@misc{BorndoerferEisenblaetterGroetscheletal., author = {Bornd{\"o}rfer, Ralf and Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Martin, Alexander}, title = {The Orientation Model for Frequency Assignment Problems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5627}, number = {TR-98-01}, abstract = {Mobile telecommunication systems establish a large number of communication links with a limited number of available frequencies; reuse of the same or adjacent frequencies on neighboring links causes interference. The task to find an assignment of frequencies to channels with minimal interference is the frequency assignment problem. The frequency assignment problem is usually treated as a graph coloring problem where the number of colors is minimized, but this approach does not model interference minimization correctly. We give in this paper a new integer programming formulation of the frequency assignment problem, the orientation model, and develop a heuristic two-stage method to solve it. The algorithm iteratively solves an outer and an inner optimization problem. The outer problem decides for each pair of communication links which link gets the higher frequency and leads to an acyclic subdigraph problem with additional longest path restrictions. The inner problem to find an optimal assignment respecting an orientation leads to a min-cost flow problem.}, language = {en} } @misc{GroetschelHenk, author = {Gr{\"o}tschel, Martin and Henk, Martin}, title = {On the Representation of Polyhedra by Polynomial Inequalities}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6826}, number = {02-15}, abstract = {A beautiful result of Br{\"o}cker and Scheiderer on the stability index of basic closed semi-algebraic sets implies, as a very special case, that every \$d\$-dimensional polyhedron admits a representation as the set of solutions of at most \$d(d+1)/2\$ polynomial inequalities. Even in this polyhedral case, however, no constructive proof is known, even if the quadratic upper bound is replaced by any bound depending only on the dimension. Here we give, for simple polytopes, an explicit construction of polynomials describing such a polytope. The number of used polynomials is exponential in the dimension, but in the 2- and 3-dimensional case we get the expected number \$d(d+1)/2\$.}, language = {en} } @misc{BosseGroetschelHenk, author = {Bosse, Hartwig and Gr{\"o}tschel, Martin and Henk, Martin}, title = {Polynomial Inequalities Representing Polyhedra}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8284}, number = {04-53}, abstract = {Our main result is that every \$n\$-dimensional polytope can be described by at most \$2n-1\$ polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an \$n\$-dimensional pointed polyhedral cone we prove the bound \$2n-2\$ and for arbitrary polyhedra we get a constructible representation by \$2n\$ polynomial inequalities.}, language = {en} } @misc{BosseGroetschelHenk, author = {Bosse, Hartwig and Gr{\"o}tschel, Martin and Henk, Martin}, title = {Polynomial Inequalities Representing Polyhedra}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7473}, number = {03-25}, abstract = {Our main result is that every n-dimensional polytope can be described by at most (2n-1) polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an n-dimensional pointed polyhedral cone we prove the bound 2n-2 and for arbitrary polyhedra we get a constructible representation by 2n polynomial inequalities.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Optimum Path Packing on Wheels: The Consecutive Case}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1976}, number = {SC-95-31}, abstract = {We show that, given a wheel with nonnegative edge lengths and pairs of terminals located on the wheel's outer cycle such that the terminal pairs are in consecutive order, then a path packing, i.~e., a collection of edge disjoint paths connecting the given terminal pairs, of minimum length can be found in strongly polynomial time. Moreover, we exhibit for this case a system of linear inequalities that provides a complete and nonredundant description of the path packing polytope, which is the convex hull of all incidence vectors of path packings and their supersets.}, language = {en} } @misc{BorndoerferEisenblaetterGroetscheletal., author = {Bornd{\"o}rfer, Ralf and Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Martin, Alexander}, title = {Frequency Assignment in Cellular Phone Networks}, doi = {10.1023/A:1018908907763}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3044}, number = {SC-97-35}, abstract = {We present a graph-theoretic model for the \emph{frequency assignment problem} in Cellular Phone Networks: Obeying several technical and legal restrictions, frequencies have to be assigned to transceivers so that interference is as small as possible. This optimization problem is NP-hard. Good approximation cannot be guaranteed, unless P = NP. We describe several assignment heuristics. These heuristics are simple and not too hard to implement. We give an assessment of the heuristics' efficiency and practical usefulness. For this purpose, typical instances of frequency assignment problems with up to 4240 transceivers and 75 frequencies of a German cellular phone network operator are used. The results are satisfying from a practitioner's point of view. The best performing heuristics were integrated into a network planning system used in practice.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner Trees: Polyhedral Investigations.}, doi = {10.1007/BF02592085}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-786}, number = {SC-92-08}, abstract = {Let \$G=(V,E)\$ be a graph and \$T\subseteq V\$ be a node set. We call an edge set \$S\$ a Steiner tree with respect to \$T\$ if \$S\$ connects all pairs of nodes in \$T\$. In this paper we address the following problem, which we call the weighted Steiner tree packing problem. Given a graph \$G=(V,E)\$ with edge weights \$w_e\$, edge capacities \$c_e, e \in E,\$ and node sets \$T_1,\ldots,T_N\$, find edge sets \$S_1,\ldots,S_N\$ such that each \$S_k\$ is a Steiner tree with respect to \$T_k\$, at most \$c_e\$ of these edge sets use edge \$e\$ for each \$e\in E\$, and such that the sum of the weights of the edge sets is minimal. Our motivation for studying this problem arises from the routing problem in VLSI-design, where given sets of points have to be connected by wires. We consider the Steiner tree packing Problem from a polyhedral point of view and define an appropriate polyhedron, called the Steiner tree packing polyhedron. The goal of this paper is to (partially) describe this polyhedron by means of inequalities. It turns out that, under mild assumptions, each inequality that defines a facet for the (single) Steiner tree polyhedron can be lifted to a facet-defining inequality for the Steiner tree packing polyhedron. The main emphasis of this paper lies on the presentation of so-called joint inequalities that are valid and facet-defining for this polyhedron. Inequalities of this kind involve at least two Steiner trees. The classes of inequalities we have found form the basis of a branch \& cut algorithm. This algorithm is described in our companion paper SC 92-09.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiners Trees: A Cutting Plane Algorithm and Computational Results.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-792}, number = {SC-92-09}, abstract = {In this paper we describe a cutting plane algorithm for the Steiner tree packing problem. We use our algorithm to solve some switchbox routing problems of VLSI-design and report on our computational experience. This includes a brief discussion of separation algorithms, a new LP-based primal heuristic and implementation details. The paper is based on the polyhedral theory for the Steiner tree packing polyhedron developed in our companion paper SC 92-8 and meant to turn this theory into an algorithmic tool for the solution of practical problems.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {The Steiner Tree Packing Problem in VLSI-Design.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1328}, number = {SC-94-02}, abstract = {In this paper we describe several versions of the routing problem arising in VLSI design and indicate how the Steiner tree packing problem can be used to model these problems mathematically. We focus on switchbox routing problems and provide integer programming formulations for routing in the knock-knee and in the Manhattan model. We give a brief sketch of cutting plane algorithms that we developed and implemented for these two models. We report on computational experiments using standard test instances. Our codes are able to determine optimum solutions in most cases, and in particular, we can show that some of the instances have no feasible solution if Manhattan routing is used instead of knock-knee routing.}, language = {en} } @misc{FerreiraGroetschelKiefletal., author = {Ferreira, Carlos E. and Gr{\"o}tschel, Martin and Kiefl, Stefan and Krispenz, Ludwig and Martin, Alexander and Weismantel, Robert}, title = {Some Integer Programs Arising in the Design of Main Frame Computers.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-957}, number = {SC-92-25}, abstract = {In this paper we describe and discuss a problem that arises in the (global) design of a main frame computer. The task is to assign certain functional units to a given number of so called multi chip modules or printed circuit boards taking into account many technical constraints and minimizing a complex objective function. We describe the real world problem. A thorough mathematical modelling of all aspects of this problem results in a rather complicated integer program that seems to be hopelessly difficult -- at least for the present state of integer programming technology. We introduce several relaxations of the general model, which are also \$NP\$-hard, but seem to be more easily accessible. The mathematical relations between the relaxations and the exact formulation of the problem are discussed as well.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Routing in Grid Graphs by Cutting Planes.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-967}, number = {SC-92-26}, abstract = {{\def\N{{\cal N}} \def\R{\hbox{\rm I\kern-2pt R}} \def\MN{{\rm I\kern-2pt N}} In this paper we study the following problem, which we call the weighted routing problem. Let be given a graph \$G=(V,E)\$ with non-negative edge weights \$w_e\in\R_+\$ and integer edge capacities \$c_e\in\MN\$ and let \$\N=\{T_1,\ldots,T_N\}\$, \$N\ge 1\$, be a list of node sets. The weighted routing problem consists in finding edge sets \$S_1,\ldots,S_N\$ such that, for each \$k\in\{1,\ldots,N\}\$, the subgraph \$(V(S_k),S_k)\$ contains an \$[s,t]\$-path for all \$s,t\in T_k\$, at most \$c_e\$ of these edge sets use edge \$e\$ for each \$e\in E\$, and such that the sum of the weights of the edge sets is minimal. Our motivation for studying this problem arises from the routing problem in VLSI-design, where given sets of points have to be connected by wires. We consider the weighted routing problem from a polyhedral point of view. We define an appropriate polyhedron and try to (partially) describe this polyhedron by means of inequalities. We briefly sketch our separation algorithms for some of the presented classes of inequalities. Based on these separation routines we have implemented a branch and cut algorithm. Our algorithm is applicable to an important subclass of routing problems arising in VLSI-design, namely to problems where the underlying graph is a grid graph and the list of node sets is located on the outer face of the grid. We report on our computational experience with this class of problem instances.}}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner Trees: Further Facets.}, doi = {10.1006/eujc.1996.0004}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-975}, number = {SC-93-01}, abstract = {In this paper we continue the investigations in [GMW92a] for the \def\sbppo{Steiner tree packing polyhedron} \sbppo. We present several new classes of valid inequalities and give sufficient (and necessary) conditions for these inequalities to be facet-defining. It is intended to incorporate these inequalities into an existing cutting plane algorithm that is applicable to practical problems arising in the design of electronic circuits.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner Trees: Separation Algorithms.}, doi = {10.1137/S0895480193258716}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-984}, number = {SC-93-02}, abstract = {In this paper we investigate separation problems for classes of inequalities valid for the polytope associated with the Steiner tree packing problem, a problem that arises, e.~g., in VLSI routing. The separation problem for Steiner partition inequalities is \${\cal N}\hskip-2pt{\cal P}\$-hard in general. We show that it can be solved in polynomial time for those instances that come up in switchbox routing. Our algorithm uses dynamic programming techniques. These techniques are also applied to the much more complicated separation problem for alternating cycle inequalities. In this case we can compute in polynomial time, given some point \$y\$, a lower bound for the gap \$\alpha-a^Ty\$ over all alternating cycle inequalities \$a^Tx\ge\alpha\$. This gives rise to a very effective separation heuristic. A by-product of our algorithm is the solution of a combinatorial optimization problem that is interesting in its own right: Find a shortest path in a graph where the ``length'' of a path is its usual length minus the length of its longest edge.}, language = {en} } @misc{GroetschelMartinWeismantel, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Optimum Path Packing on Wheels: The Noncrossing Case.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1225}, number = {SC-93-26}, abstract = {We show that, given a wheel with nonnegative edge lengths and pairs of terminals located on the wheel's outer cycle such that no two terminal pairs cross, then a path packing, i.~e.,a collection of edge disjoint paths connecting the given terminal pairs, of minimum length can be found in strongly polynomial time. Moreover, we exhibit for this case a system of linear inequalities that provides a complete and nonredundant description of the path packing polytope, which is the convex hull of all incidence vectors of path packings and their supersets.}, language = {en} } @article{BosseGroetschelHenk2005, author = {Bosse, Hartwig and Gr{\"o}tschel, Martin and Henk, Martin}, title = {Polynomial inequalities representing polyhedra}, series = {Mathematical Programming}, volume = {103}, journal = {Mathematical Programming}, number = {1}, doi = {10.1007/s10107-004-0563-2}, pages = {35 -- 44}, year = {2005}, language = {en} } @inproceedings{GroetschelMartinWeismantel1993, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Routing in grid graphs by cutting planes}, series = {Integer Programming and Combinatorial Optimization. Proceedings of a Conference held at Centro Ettore Majorana, Erice, Italy, April 29 - May 1, 1993}, booktitle = {Integer Programming and Combinatorial Optimization. Proceedings of a Conference held at Centro Ettore Majorana, Erice, Italy, April 29 - May 1, 1993}, editor = {Rinaldi, Giovanni and Wolsey, Laurence}, publisher = {Librarian CORE}, address = {Louvain-la-Neuve}, pages = {447 -- 461}, year = {1993}, language = {en} } @article{GroetschelMartinWeismantel1997, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {The Steiner tree packing problem in VLSI design}, series = {Mathematical Programming}, volume = {78}, journal = {Mathematical Programming}, number = {2}, pages = {265 -- 281}, year = {1997}, language = {en} } @article{BorndoerferEisenblaetterGroetscheletal.1998, author = {Bornd{\"o}rfer, Ralf and Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Martin, Alexander}, title = {Frequency assignment in cellular phone networks}, series = {Annals of Operations Research}, volume = {76}, journal = {Annals of Operations Research}, publisher = {J. C. Baltzer AG, Science Publishers}, doi = {10.1023/A:1018908907763}, pages = {73 -- 93}, year = {1998}, language = {en} } @article{GroetschelMartinWeismantel1995, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Routing in Grid Graphs by Cutting Planes}, series = {ZOR - Mathematical Methods of Operations Research}, volume = {41}, journal = {ZOR - Mathematical Methods of Operations Research}, number = {3}, pages = {255 -- 275}, year = {1995}, language = {en} } @article{GroetschelMartinWeismantel1996, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner Trees: Further Facets}, series = {European Journal of Combinatorics}, volume = {17}, journal = {European Journal of Combinatorics}, number = {1}, doi = {10.1006/eujc.1996.0004}, pages = {39 -- 52}, year = {1996}, language = {en} } @article{GroetschelMartinWeismantel1996, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner Trees: Separation Algorithms}, series = {SIAM Journal on Discrete Mathematics}, volume = {9}, journal = {SIAM Journal on Discrete Mathematics}, number = {2}, doi = {10.1137/S0895480193258716}, pages = {233 -- 257}, year = {1996}, language = {en} } @article{GroetschelMartinWeismantel1996, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Optimum Path Packing on Wheels}, series = {Computers and Mathematics with Applications}, volume = {31}, journal = {Computers and Mathematics with Applications}, number = {11}, publisher = {Elsevier}, pages = {23 -- 35}, year = {1996}, language = {en} } @article{GroetschelMartinWeismantel1996, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner trees: Polyhedral Investigations}, series = {Mathematical Programming, Series A}, volume = {72}, journal = {Mathematical Programming, Series A}, number = {2}, doi = {10.1007/BF02592085}, pages = {101 -- 123}, year = {1996}, language = {en} } @article{GroetschelMartinWeismantel1996, author = {Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert}, title = {Packing Steiner trees: a cutting plane algorithm and computational results}, series = {Mathematical Programming, Series A}, volume = {72}, journal = {Mathematical Programming, Series A}, number = {2}, doi = {10.1007/BF02592086}, pages = {125 -- 145}, year = {1996}, language = {en} } @article{GroetschelHenk2003, author = {Gr{\"o}tschel, Martin and Henk, Martin}, title = {The Representation of Polyhedra by Polynomial Inequalities}, series = {Discrete \& Computational Geometry}, volume = {29}, journal = {Discrete \& Computational Geometry}, number = {4}, doi = {10.1007/s00454-003-0782-y}, pages = {485 -- 504}, year = {2003}, language = {en} } @article{FerreiraGroetschelMartinetal.1993, author = {Ferreira, Carlos and Gr{\"o}tschel, Martin and Martin, Alexander and Weismantel, Robert and Kiefl, Stefan and Krispenz, Ludwig}, title = {Some Integer Programs Arising in the Design of Main Frame Computers}, series = {ZOR - Methods and Models of Operations Research}, volume = {38}, journal = {ZOR - Methods and Models of Operations Research}, number = {1}, pages = {77 -- 100}, year = {1993}, language = {en} } @inproceedings{BorndoerferEisenblaetterGroetscheletal.1996, author = {Bornd{\"o}rfer, Ralf and Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Martin, Alexander}, title = {Stable-Set and Other Techniques for Frequency Assignment Problems}, series = {Anais da I Oficina Nacional em Problemas de Corte \& Empacotamento}, booktitle = {Anais da I Oficina Nacional em Problemas de Corte \& Empacotamento}, publisher = {Universidade de S{\~a}o Paulo, Instituto de Matem{\´a}tica e Estat{\´i}stica}, pages = {17 -- 21}, year = {1996}, language = {en} } @misc{GroetschelKuberekLilletal., author = {Gr{\"o}tschel, Martin and Kuberek, Monika and Lill, Monika and Lohrum, Stefan and L{\"u}gger, Joachim and Rusch, Beate}, title = {Kooperativer Bibliotheksverbund Berlin-Brandenburg (KOBV)}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6118}, number = {00-43}, abstract = {Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) wurde in den Jahren 1997-2000 im Rahmen eines wissenschaftlichen Projektes eingerichtet. Er stellt eine neuartige Form von Bibliotheksverbund dar. Sein technisches Konzept und sein organisatorischer Aufbau basieren auf der Internetphilosophie. Den informationstechnischen Kern bildet eine Suchmaschine, die die heterogenen lokalen Bibliothekssysteme miteinander verbindet. Die KOBV-Organisation ist dezentral. Sie wird getragen von der Kooperation der Bibliotheken in Berlin und Brandenburg; diese werden von einer kleinen Verbundzentrale unterst{\"u}tzt. Die KOBV-Suchmaschine ist zu erreichen unter: {\begin{rawhtml} http://www.kobv.de/suche/ \end{rawhtml}}}, language = {de} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Mathematik in der Industrie: interessante Branchen und zuk{\"u}nftige Einsatzfelder}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6125}, number = {00-44}, abstract = {Dieser kurze Artikel hat keine umfassende {\"U}bersicht zum Ziel. Basierend auf eigenen Erfahrungen durch Projekte mit Industriefirmen m{\"o}chte ich einige Branchen erw{\"a}hnen, bei denen nach meiner Einsch{\"a}tzung Mathematik in Zukunft zunehmend Anwendung finden wird. Ich werde das anhand konkreter Beispiele erl{\"a}utern. Mathematik ersetzt in der Regel traditionelle Analyse-, Planungs- und Entwurfstechniken. Den (nicht leichten) Schritt zum Einsatz mathematischer Methoden macht ein Praktiker nur, wenn es sich f{\"u}r ihn ``lohnt''. Wann sich dies lohnt, ist schwer abzusch{\"a}tzen. Man kann aber einige Indikatoren daf{\"u}r finden, ob eine Branche f{\"u}r den Einsatz von Mathematik ``reif'' ist. Ob es dann dazu kommt, h{\"a}ngt von vielen Faktoren ab, nicht zuletzt von der Psychologie und dem sozialen Umfeld der beteiligten Personen sowie der Bereitschaft, sich auf ein so schwieriges Terrain zu begeben und Kompromisse einzugehen. Gerade letzteres f{\"a}llt Mathematikern gelegentlich schwer.}, language = {de} } @misc{EisenblaetterGroetschelKoster, author = {Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Koster, Arie M.C.A.}, title = {Frequency Planning and Ramifications of Coloring}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6152}, number = {00-47}, abstract = {This paper surveys frequency assignment problems coming up in planning wireless communication services. It particularly focuses on cellular mobile phone systems such as GSM, a technology that revolutionizes communication. Traditional vertex coloring provides a conceptual framework for the mathematical modeling of many frequency planning problems. This basic form, however, needs various extensions to cover technical and organizational side constraints. Among these ramifications are \$T\$-coloring and list coloring. To model all the subtleties, the techniques of integer programming have proven to be very useful. The ability to produce good frequency plans in practice is essential for the quality of mobile phone networks. The present algorithmic solution methods employ variants of some of the traditional coloring heuristics as well as more sophisticated machinery from mathematical programming. This paper will also address this issue. Finally, this paper discusses several practical frequency assignment problems in detail, states the associated mathematical models, and also points to public electronic libraries of frequency assignment problems from practice. The associated graphs have up to several thousand nodes and range from rather sparse to almost complete.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Telota - was soll das?}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6538}, number = {01-27}, abstract = {Telota ist ein Kunstwort, das f{\"u}r alle Aktivit{\"a}ten der Berlin-Brandenburgischen Akademie der Wissenschaften steht, die der F{\"o}rderung von Forschung, Kommunikation und Pr{\"a}sentation durch elektronische Medien dienen. In diesem Artikel werden die Entstehung des Telota-Projektes geschildert und die Ziele diskutiert, die mit diesem Projekt erreicht werden sollen. Es geht darum, moderne Informationstechnik bewusst, geplant und nachhaltig f{\"u}r alle Belange der {\rm BBAW} einzusetzen. Informationstechnische Werkzeuge sollen f{\"u}r die wissenschaftliche Arbeit effizient genutzt werden; die Information nach innen und nach außen soll deutlich verbessert werden; eine bessere Kommunikationsinfrastuktur soll die Zusammenarbeit f{\"o}rdern.}, language = {de} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Empfehlungen des Wissenschaftsrates zur digitalen Informationsversorgung durch Hochschulbibliotheken}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6546}, number = {01-28}, abstract = {Der Wissenschaftsrat hat in seiner Juli-Sitzung 2001 \glqq Empfehlungen zur digitalen Informationsversorgung durch Hochschulbibliotheken \grqq verabschiedet. Einige der Vorschl{\"a}ge des Wissenschaftsrates k{\"o}nnen, falls sie von den angesprochenen Institutionen aufgenommen werden, zu einer nachhaltigen Ver{\"a}nderung der wissenschaftlichen Informationslandschaft f{\"u}hren. In meinem kurzen Kommentar zu diesem Papier m{\"o}chte ich auf einige dieser Anregungen hinweisen.}, language = {de} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Mein digitaler Traum}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6558}, number = {01-29}, abstract = {Von welcher "Informationsumwelt" tr{\"a}umt jemand, der f{\"u}r seine wissenschaftliche (und sonstige) Arbeit digitale Informationstechnologie intensiv einsetzt? In diesem Artikel beschreibe ich meinen "digitalen Traum". Er ist ganz einfach zu formulieren:"Ich will alles und zwar sofort, jederzeit, "{\"u}berall" und kostenlos zur Verf{\"u}gung haben." Ich schildere, was davon heute schon (fast) realisiert ist und was noch fehlt. Ich skizziere einige zentrale Schwierigkeiten der vollst{\"a}ndigen Realisierung und skizziere m{\"o}gliche L{\"o}sungen.}, language = {de} } @misc{EisenblaetterGroetschelKoster, author = {Eisenbl{\"a}tter, Andreas and Gr{\"o}tschel, Martin and Koster, Arie M.C.A.}, title = {Frequenzplanung im Mobilfunk}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6762}, number = {02-09}, abstract = {Telekommunikation ist seit Jahren \glqq in\grqq. Zun{\"a}chst gab es einen enormen Aufschwung; neue Technologien und Dienste haben eine {\"u}berw{\"a}ltigende, nicht vorhersehbare Akzeptanz gefunden. Derzeit ist -- ausgel{\"o}st durch die UMTS-Lizenzversteigerungen, Rezessions- und S{\"a}ttigungstendenzen -- eine Krise zu verzeichnen. Viele (auch wir) sind davon {\"u}berzeugt, dass technischer Fortschritt und n{\"u}tzliche Dienste demn{\"a}chst die Stimmung wieder {\"a}ndern werden. Wenigen ist allerdings bewusst, welche Rolle Mathematik bei der Entwicklung und dem effizienten Einsatz vieler der neuen Kommunikationstechnologien spielt. In diesem Artikel soll kein {\"U}berblick {\"u}ber diesen umfangreichen Themenkreis gegeben werden. Wir zeigen lediglich an einem konkreten Beispiel aus dem Mobilfunk, der Frequenzplanung in GSM-Funknetzen, was man durch geeignete Modellierung der praktischen Fragestellung und den Einsatz problemad{\"a}quater Algorithmen erreichen kann.}, language = {de} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Neueste Entwicklungen der Informations- und Kommunikationstechnik und ihre Auswirkungen auf den Wissenschaftsbetrieb}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5417}, number = {TR-96-12}, abstract = {Dieser Aufsatz ist die Ausarbeitung eines Vortrags auf der 4. Jahrestagung der Gesellschaft Information Bildung (GIB) am 10. und 11. Oktober 1996 an der Humboldt-Universit{\"a}t Berlin. Er enth{\"a}lt einen {\"U}berblick {\"u}ber die neuesten Entwicklungen in der Informations- und Kommunikationstechnik und beleuchtet deren Auswirkungen auf den Wissenschaftsbetrieb. Er beginnt mit historischen Anmerkungen zur Entstehung der Schrift und zur Speicherung und {\"U}bertragung von Information. Er f{\"u}hrt, nach einer knappen Diskussion der Defizite in der gegenw{\"a}rtigen Informationsversorgung und einem kurzen Ausflug in die Geschichte des Internet und des World Wide Web, zu einer Darstellung ausgew{\"a}hlter aktueller Aktivit{\"a}ten der Wissenschaften im Bereich elektronischer Information, Kommunikation, Dokumentation und Archivierung. Dabei zeigt sich, dass sich der Begriff wissenschaftlicher Information bereits zu wandeln beginnt. Zur traditionellen papiergebundenen Information treten v{\"o}llig neue Informationsarten hinzu, von Software- und Datensammlungen {\"u}ber multimediale Information bis hin zu Fern{\"u}bertagungen von wissenschaftlichen Vortr{\"a}gen und Experimenten. Eine Vielzahl von Links; (URL's bzw. anklickbaren Verweisen) soll diesen Wandel nicht nur belegen, sondern auch das rasche Auffinden wichtiger Dokumente und Quellen im Internet erm{\"o}glichen.}, language = {de} } @misc{DalitzGroetschelHeyeretal., author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and Heyer, Gernot and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Informationsdienste f{\"u}r die Mathematik im Internet (Math-Net)}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5421}, number = {TR-96-13}, abstract = {Der Informationsaustausch in den Wissenschaften befindet sich in einer Umbruchsituation. Traditionelle, papiergebundene Publikationsformen werden durch elektronische Medien erg{\"a}nzt und sogar abgel{\"o}st. Moderne Client/Server basierende Systeme und Zugriffswerkzeuge erlauben heute v{\"o}llig neue Distributions- und Kommunikationsformen. In einem vom DFN und der Deutschen Telekom gef{\"o}rderten Projekt geht es in der vorliegenden Vorhabenbeschreibung um die konkrete inhaltliche und organisatorische Planung, ein umfassendes, m{\"o}glichst alle mathematisch relevanten Ressourcen ber{\"u}cksichtigendes, Informationssystem f{\"u}r die Mathematik aufzubauen.}, language = {de} } @misc{GroetschelKrumkeRambauetal., author = {Gr{\"o}tschel, Martin and Krumke, Sven and Rambau, J{\"o}rg and Torres, Luis Miguel}, title = {Making the Yellow Angels Fly: Online Dispatching Of Service Vehicles in Real Time}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6858}, number = {02-18}, abstract = {Combinatorial online optimization is an area with lots of applications and potential for significant progress, both in theory and practice. In this short note we sketch the ADACproblem, a typical large-scale online optimization problem, discuss some theoretical and pratical issues coming up, and explain, very briefly, how we approach this problem mathematically. Online problems are a battlefield of heuristics with many strong claims about their solution quality. We indicate that a stronger problem orientation and the use of a little more mathematics may yield.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Cardinality Homogeneous Set Systems, Cycles in Matroids, and Associated Polytopes}, doi = {10.1137/1.9780898718805.ch8}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6868}, number = {02-19}, abstract = {A subset \${\cal C}\$ of the power set of a finite set \$E\$ is called cardinality homogeneous if, whenever \${\cal C}\$ contains some set \$F\$, \${\cal C}\$ contains all subsets of \$E\$ of cardinality \$|F|\$. Examples of such set systems \${\cal C}\$ are the sets of circuits and the sets of cycles of uniform matroids and the sets of all even or of all odd cardinality subsets of \$E\$. With each cardinality homogeneous set system \${\cal C}\$, we associate the polytope \$P({\cal C})\$, the convex hull of the incidence vectors of all sets in \${\cal C}\$, and provide a complete and nonredundant linear description of \$P({\cal C})\$. We show that a greedy algorithm optimizes any linear function over \$P({\cal C})\$, give an explicit optimum solution of the dual linear program, and provide a polynomial time separation algorithm for the class of polytopes of type \$P({\cal C})\$.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {P=NP?}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6939}, number = {02-26}, abstract = {Hinter der f{\"u}r den Uneingeweihten etwas kryptischen Frage "P = NP?" verbirgt sich das derzeit wichtigste Problem der Komplexit{\"a}tstheorie. Dieser Artikel erl{\"a}utert einige Aspekte der Theorie und erkl{\"a}rt informell, was "P = NP?" bedeutet. Es geht nicht nur um komplizierte algorithmische Mathematik und Informatik, sondern um grunds{\"a}tzliche Fragen unserer Lebensumwelt. Kann man vielleicht beweisen, dass es f{\"u}r viele Probleme unseres Alltags keine effizienten L{\"o}sungsmethoden gibt?}, language = {de} } @misc{GroetschelKrumkeRambauetal., author = {Gr{\"o}tschel, Martin and Krumke, Sven and Rambau, J{\"o}rg and Winter, Thomas and Zimmermann, Uwe}, title = {Combinatorial Online Optimization in Real Time}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6424}, number = {01-16}, abstract = {Optimization is the task of finding an optimum solution to a given problem. When the decision variables are discrete we speak of a combinatorial optimization problem. Such a problem is online when decisions have to be made before all data of the problem are known. And we speak of a real-time online problem when online decisions have to be computed within very tight time bounds. This paper surveys the are of combinatorial online and real-time optimization, it discusses, in particular, the concepts with which online and real-time algorithms can be analyzed.}, language = {en} } @misc{GroetschelKrumkeRambau, author = {Gr{\"o}tschel, Martin and Krumke, Sven and Rambau, J{\"o}rg}, title = {Online Optimization of Complex Transportation Systems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6438}, number = {01-17}, abstract = {This paper discusses online optimization of real-world transportation systems. We concentrate on transportation problems arising in production and manufacturing processes, in particular in company internal logistics. We describe basic techniques to design online optimization algorithms for such systems, but our main focus is decision support for the planner: which online algorithm is the most appropriate one in a particular setting? We show by means of several examples that traditional methods for the evaluation of online algorithms often do not suffice to judge the strengths and weaknesses of online algorithms. We present modifications of well-known evaluation techniques and some new methods, and we argue that the selection of an online algorithm to be employed in practice should be based on a sound combination of several theoretical and practical evaluation criteria, including simulation.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Copyright und elektronisches Publizieren: Auf dem Weg zu vern{\"u}nftigen Regelungen?}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6395}, number = {01-13}, abstract = {Das \emph{Committee on Electronic Information and Communication} (CEIC) der \emph{International Mathematical Union} (IMU) hat die Aufgabe, sich {\"u}ber die langfristige Informationsversorgung in der Mathematik Gedanken zu machen und L{\"o}sungsvorschl{\"a}ge hierf{\"u}r zu erarbeiten. Das Kernthema ist nat{\"u}rlich "`Elektronisches Publizieren"'. Dazu geh{\"o}ren auch Copyright-Regelungen. \% Sie sind -- \% neben einer Andeutung der weiteren CEIC-Pl{\"a}ne -- der Fokus dieses \% kurzen Artikels. Er schließt mit einem von der IMU verabschiedeten \% Aufruf zu vern{\"u}nftigem Verhalten bei Copyright-Vereinbarungen. Eine \% nachhaltige Befolgung dieses Aufrufs -- verbunden mit weiteren \% Aktivit{\"a}ten -- k{\"o}nnte die (derzeit kaum noch bezahlbare und \% dadurch gef{\"a}hrdete) Literaturversorgung nachhaltig zum Positiven \% ver{\"a}ndern. Mit diesem Artikel beginnt eine kleine Serie von Aufs{\"a}tzen, in denen ich (in meiner Funktion als eines von elf CEIC-Mitgliedern) die Empfehlungen des CEIC erl{\"a}utern werde. \% Das heutige Thema sind die \% CEIC-Vorschl{\"a}ge zum Copyright}, language = {de} } @misc{BorndoerferGroetschelLukacetal.2005, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Lukac, Sascha and Mitusch, Kay and Schlechte, Thomas and Schultz, S{\"o}ren and Tanner, Andreas}, title = {An Auctioning Approach to Railway Slot Allocation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8786}, number = {05-45}, year = {2005}, abstract = {We present an approach to implement an auction of railway slots. Railway network, train driving characteristics, and safety requirements are described by a simplified, but still complex macroscopic model. In this environment, slots are modelled as combinations of scheduled track segments. The auction design builds on the iterative combinatorial auction. However, combinatorial bids are restricted to some types of slot bundles that realize positive synergies between slots. We present a bidding language that allows bidding for these slot bundles. An integer programming approach is proposed to solve the winner determination problem of our auction. Computational results for auction simulations in the Hannover-Fulda-Kassel area of the German railway network give evidence that auction approaches can induce a more efficient use of railway capacity.}, language = {en} } @misc{BorndoerferGroetschelPfetsch, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Pfetsch, Marc}, title = {A Column-Generation Approach to Line Planning in Public Transport}, doi = {/10.1287/trsc.1060.0161}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8522}, number = {05-18}, abstract = {The line planning problem is one of the fundamental problems in strategic planning of public and rail transport. It consists in finding lines and corresponding frequencies in a transport network such that a given travel demand can be satisfied. There are (at least) two objectives. The transport company wishes to minimize operating costs, the passengers want to minimize travel times. We propose a n ew multi-commodity flow model for line planning. Its main features, in comparison to existing models, are that the passenger paths can be freely routed and that the lines are generated dynamically. We discuss properties of this model and investigate its complexity. Results with data for the city of Potsdam, Germany, are reported.}, language = {en} } @misc{BorndoerferGroetschelPfetsch, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Pfetsch, Marc}, title = {Public Transport to the fORe!}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8562}, number = {05-22}, abstract = {Can OR methods help the public transport industry to break even? The article gives evidence that there exist significant potentials in this direction, which can be harnessed by a combination of modern mathematical methods and local planning knowledge. Many of the planning steps in public transport are classical combinatorial problems, which can be solved in unprecedented size and quality due the rapid progress in large-scale optimization. Three examples on vehicle scheduling, duty scheduling, and integrated vehicle and duty scheduling illustrate the level that has been reached and the improvements that can be achieved today. Extensions of such methods to further questions of strategic, online, and market-oriented planning are currently investigated. In this way, OR can make a significant contribution to answer the basic but extremely difficult question ``What is a good public transport network?.}, language = {en} } @misc{GroetschelRoggenbuckSperber, author = {Gr{\"o}tschel, Martin and Roggenbuck, Robert and Sperber, Wolfram}, title = {Entwicklung und Aufbau des Internet-Dienstes "Math\&Industry"}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8573}, number = {05-23}, abstract = {Die Anwendung mathematischer Methoden und Verfahren wird immer mehr zur Voraussetzung innovativer Produkte und Dienstleistungen. Um neue Produkte und Dienstleistungen zu entwickeln, m{\"u}ssen die Produktions- und technologischen Prozesse mathematisch modelliert, beschrieben und optimiert werden. Diesen Umstand Rechnung tragend, hat das Bundesministerium f{\"u}r Bildung und Forschung (BMBF) 1993 begonnen, den Einsatz mathematischer Verfahren und Methoden in der Mathematik {\"u}ber ein spezielles Mathematikprogramm zu f{\"o}rdern. Inzwischen hat die vierte F{\"o}rderperiode des Mathematikprogramms begonnen. \par Das Medium Internet und insbesondere das WWW sind f{\"u}r die Sichtbarkeit und Transparenz wissenschaftlicher Resultate in den letzten zehn Jahren immer wichtiger geworden. Wer nicht im Web "'sichtbar"' ist, l{\"a}uft Gefahr, nicht wahrgenommen zu werden. Intention und Ziel des durchgef{\"u}hrten Projekts war es, ein Konzept f{\"u}r eine qualitativ hochwertige und umfassende Darstellung des BMBF Mathematikprogramms, insbesondere der in den Projekten erzielten Ergebnisse, zu entwickeln und zu realisieren und damit den Stellenwert und die Akzeptanz mathematischer Forschung in der Gesellschaft zu festigen und den Wissenstransfer zwischen mathematischer Forschung sowie Forschung und Entwicklung in der Wirtschaft und dem Dienstleistungsbereich zu f{\"o}rdern.}, language = {de} } @misc{BorndoerferGroetschelPfetsch, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Pfetsch, Marc}, title = {Models for Line Planning in Public Transport}, doi = {10.1007/978-3-540-73312-6_18}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7854}, number = {04-10}, abstract = {The \emph{line planning problem} is one of the fundamental problems in strategic planning of public and rail transport. It consists of finding lines and corresponding frequencies in a public transport network such that a given travel demand can be satisfied. There are (at least) two objectives. The transport company wishes to minimize its operating cost; the passengers request short travel times. We propose two new multi-commodity flow models for line planning. Their main features, in comparison to existing models, are that the passenger paths can be freely routed and that the lines are generated dynamically.}, language = {en} } @misc{LuceDuintjerTebbensLiesenetal., author = {Luce, Robert and Duintjer Tebbens, Jurjen and Liesen, J{\"o}rg and Nabben, Robert and Gr{\"o}tschel, Martin and Koch, Thorsten and Schenk, Olaf}, title = {On the Factorization of Simplex Basis Matrices}, organization = {TU Berlin, Zuse Institute Berlin, University of Basel}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-11392}, number = {09-24}, abstract = {In the simplex algorithm, solving linear systems with the basis matrix and its transpose accounts for a large part of the total computation time. We investigate various methods from modern numerical linear algebra to improve the computation speed of the basis updates arising in LPs. The experiments are executed on a large real-world test set. The most widely used solution technique is sparse LU factorization, paired with an updating scheme that allows to use the factors over several iterations. Clearly, small number of fill-in elements in the LU factors is critical for the overall performance. Using a wide range of LPs we show numerically that after a simple permutation the non-triangular part of the basis matrix is so small, that the whole matrix can be factorized with (relative) fill-in close to the optimum. This permutation has been exploited by simplex practitioners for many years. But to our knowledge no systematic numerical study has been published that demonstrates the effective reduction to a surprisingly small non-triangular problem, even for large scale LPs. For the factorization of the non-triangular part most existing simplex codes use some variant of dynamic Markowitz pivoting, which originated in the late 1950s. We also show numerically that, in terms of fill-in and in the simplex context, dynamic Markowitz is quite consistently superior to other, more recently developed techniques.}, language = {en} } @misc{GroetschelRoggenbuckSperberetal., author = {Gr{\"o}tschel, Martin and Roggenbuck, Robert and Sperber, Wolfram and Dalitz, Wolfgang}, title = {Weiterentwicklung und Ausbau des Internet-Informationsdienstes "Math\&Industry"}, organization = {ZIB}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10584}, number = {08-06}, abstract = {Mit dem Informationsdienst Math\&Industry soll ein Prototyp eines dezentralen Informationssystems f{\"u}r F{\"o}rderprogramme und Forschungsprojekte geschaffen werden, das sich auf andere Programme (bez{\"u}glich angewandter Mathematik, aber auch dar{\"u}ber hinaus) {\"u}bertragen l{\"a}sst. Das betrifft sowohl die Konzeption (Strukturierung der Informationen) als auch die Werkzeuge, die anderen BMBF-F{\"o}rderprogrammen zur Verf{\"u}gung gestellt werden k{\"o}nnen. Damit sollen diese in die Lage versetzt werden, die in Math\&Industry entwickelten Konzepte und Werkzeuge an ihre spezifischen Bed{\"u}rfnisse anzupassen.}, language = {de} } @misc{BorndoerferGroetschelJaeger, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Jaeger, Ulrich}, title = {Planning Problems in Public Transit}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-11252}, number = {09-13}, abstract = {Every day, millions of people are transported by buses, trains, and airplanes in Germany. Public transit (PT) is of major importance for the quality of life of individuals as well as the productivity of entire regions. Quality and efficiency of PT systems depend on the political framework (state-run, market oriented) and the suitability of the infrastructure (railway tracks, airport locations), the existing level of service (timetable, flight schedule), the use of adequate technologies (information, control, and booking systems), and the best possible deployment of equipment and resources (energy, vehicles, crews). The decision, planning, and optimization problems arising in this context are often gigantic and "scream" for mathematical support because of their complexity. This article sketches the state and the relevance of mathematics in planning and operating public transit, describes today's challenges, and suggests a number of innovative actions. The current contribution of mathematics to public transit is — depending on the transportation mode — of varying depth. Air traffic is already well supported by mathematics. Bus traffic made significant advances in recent years, while rail traffic still bears significant opportunities for improvements. In all areas of public transit, the existing potentials are far from being exhausted. For some PT problems, such as vehicle and crew scheduling in bus and air traffic, excellent mathematical tools are not only available, but used in many places. In other areas, such as rolling stock rostering in rail traffic, the performance of the existing mathematical algorithms is not yet sufficient. Some topics are essentially untouched from a mathematical point of view; e.g., there are (except for air traffic) no network design or fare planning models of practical relevance. PT infrastructure construction is essentially devoid of mathematics, even though enormous capital investments are made in this area. These problems lead to questions that can only be tackled by engineers, economists, politicians, and mathematicians in a joint effort. Among other things, the authors propose to investigate two specific topics, which can be addressed at short notice, are of fundamental importance not only for the area of traffic planning, should lead to a significant improvement in the collaboration of all involved parties, and, if successful, will be of real value for companies and customers: • discrete optimal control: real-time re-planning of traffic systems in case of disruptions, • model integration: service design in bus and rail traffic. Work on these topics in interdisciplinary research projects could be funded by the German ministry of research and education (BMBF), the German ministry of economics (BMWi), or the German science foundation (DFG).}, language = {en} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {E-Learning and the Working Mathematician}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-11455}, number = {09-29}, abstract = {Eigentlich war der erste Autor nur zu einem Grußwort zur Tagung „GML² 2009 - Grundfragen Multi¬medialen Lehrens und Lernens" eingeladen. Daraus wurde ein E-Learning-bezogener Vortrag, der - basierend auf Erfahrungen im Fach Mathematik - einen kritischen Blick auf die E-Learning-Szene in Deutschland wirft und diese mit entsprechenden Aktivit{\"a}ten weltweit vergleicht. Dies ist die in seinen mathematischen Teilen gek{\"u}rzte, in den E-Learning-Anteilen ein wenig erweiterte schriftliche Fassung des Vortrags. Der Artikel stammt nicht von E-Learning-Spezialisten sondern von Personen, die sich seit fast zwanzig Jahren mit elektronischer Information und Kommunikation (kurz: IuK) - insbesondere in der Mathematik - besch{\"a}ftigen. Nach einer Definition von Michael Kerres kennzeichnet der Begriff E-Learning (electronic learning - elektronisch unterst{\"u}tztes Lernen) alle Formen von Lernen, bei denen digitale Medien f{\"u}r die Pr{\"a}sentation und Distribution von Lernmaterialien und/oder zur Unterst{\"u}tzung zwischenmenschlicher Kommunikation zum Einsatz kommen, siehe z.B. http://de.wikipedia.org/wiki/E-Learning. IuK und E-Learning haben nach dieser Begriffsbildung viele Ber{\"u}hrungspunkte. Deswegen wagen wir es, unsere positiven und negativen Erfahrungen im Bereich IuK in diesem Er{\"o}ffnungsvortrag zu berichten, einige Entwicklungslinien zu vergleichen und eine eigene Kurzversion der Definition von E-Learning (besser E-Teaching and -Learning) voranzustellen: „Lehren und Lernen mit Unterst{\"u}tzung elektronischer Hilfsmittel".}, language = {de} } @misc{BorndoerferGroetschelJaeger, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Jaeger, Ulrich}, title = {Planung von {\"o}ffentlichem Personenverkehr}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10744}, number = {08-20}, abstract = {Millionen von Menschen werden allein in Deutschland t{\"a}glich von Bussen, Bahnen und Flugzeugen transportiert. Der {\"o}ffentliche Personenverkehr ({\"O}V) ist von großer Bedeutung f{\"u}r die Lebensqualit{\"a}t einzelner aber auch f{\"u}r die Leistungsf{\"a}higkeit ganzer Regionen. Qualit{\"a}t und Effizienz von {\"O}V-Systemen h{\"a}ngen ab von politischen Rahmenbedingungen (staatlich geplant, wettbewerblich organisiert) und der Eignung der Infrastruktur (Schienensysteme, Flughafenstandorte), vom vorhandenen Verkehrsangebot (Fahr- und Flugplan), von der Verwendung angemessener Technologien (Informations-, Kontroll- und Buchungssysteme) und dem bestm{\"o}glichen Einsatz der Betriebsmittel (Energie, Fahrzeuge und Personal). Die hierbei auftretenden Entscheidungs-, Planungs- und Optimierungsprobleme sind z.T. gigantisch und "schreien" aufgrund ihrer hohen Komplexit{\"a}t nach Unterst{\"u}tzung durch Mathematik. Dieser Artikel skizziert den Stand und die Bedeutung des Einsatzes von Mathematik bei der Planung und Durchf{\"u}hrung von {\"o}ffentlichem Personenverkehr, beschreibt die bestehenden Herausforderungen und regt zukunftsweisende Maßnahmen an.}, language = {de} } @misc{GroetschelLutzWestphal, author = {Gr{\"o}tschel, Martin and Lutz-Westphal, Brigitte}, title = {Diskrete Mathematik und ihre Anwendungen: Auf dem Weg zu authentischem Mathematikunterricht}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10758}, number = {08-21}, abstract = {Das heutige Leben ist durchdrungen von komplexen Technologien. Ohne Kommunikationsnetze, Internet, Mobilfunk, Logistik, Verkehrstechnik, medizinische Apparate, etc. k{\"o}nnte die moderne Gesellschaft nicht funktionieren. Fast alle dieser Technologien haben einen hohen Mathematikanteil. Der "normale B{\"u}rger"' weiss davon nichts, der Schulunterricht k{\"o}nnte dem ein wenig abhelfen. Einige mathematische Aspekte dieser Technologien sind einfach und sogar spielerisch intuitiv zug{\"a}nglich. Solche Anwendungen, die zus{\"a}tzlich noch der Lebensumwelt der Sch{\"u}ler zugeh{\"o}ren, k{\"o}nnen dazu genutzt werden, die mathematische Modellierung, also die mathematische Herangehensweise an die L{\"o}sung praktischer Fragen, anschaulich zu erl{\"a}utern. Gerade in der diskreten Mathematik k{\"o}nnen hier, quasi "nebenbei" mathematische Theorien erarbeitet und Teilaspekte (Definitionen, Fragestellungen, einfache Sachverhalte) durch eigenst{\"a}ndiges Entdecken der Sch{\"u}ler entwickelt werden. Wir beginnen mit einigen Beispielen.}, language = {de} } @misc{AbboudGroetschelKoch, author = {Abboud, Nadine and Gr{\"o}tschel, Martin and Koch, Thorsten}, title = {Mathematical Methods for Physical Layout of Printed Circuit Boards: An Overview}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9231}, number = {06-29}, abstract = {This article surveys mathematical models and methods used for physical PCB layout, i.e., component placement and wire routing. The main concepts are briefly described together with relevant references.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Das Problem mit der Komplexit{\"a}t: P = NP?}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8916}, number = {05-58}, abstract = {Was Komplexit{\"a}t ist, weiß niemand so richtig. In vielen Wissenschaftsgebieten wird der Begriff Komplexit{\"a}t verwendet, {\"u}berall mit etwas anderer Bedeutung. Mathematik und Informatik hab en eine eigene Theorie hierzu entwickelt: die Komplexit{\"a}tstheorie. Sie stellt zwar grundlegende Begriffe bereit, aber leider sind die meisten wichtigen Fragestellungen noch ungel{\"o}st. Diese kurze Einf{\"u}hrung konzentriert sich auf einen speziellen, aber bedeutenden Aspekt der Theorie: L{\"o}sbarkeit von Problemen in deterministischer und nichtdeterministischer polynomialer Zeit. Hinter der f{\"u}r Uneingeweihte etwas kryptischen Frage "P = NP?" verbirgt sich das derzeit wichtigste Problem der Komplexit{\"a}tstheorie. Anhand dieser Fragestellung werden einige Aspekte der Theorie erl{\"a}utert und formell erkl{\"a}rt, was "P = NP?" bedeutet. Es geht nicht nur um komplizierte algorithmische Mathematik und Informatik, sondern um grunds{\"a}tzliche Fragen unserer Lebensumwelt. Kann man vielleicht beweisen, dass es f{\"u}r viele Probleme unseres Alltags keine effizienten L{\"o}sungsmethoden gibt?}, language = {de} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Schnelle Rundreisen: Das Travelling Salesman-Problem}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8901}, number = {05-57}, abstract = {Das Travelling-Salesman-Problem (TSP) ist das am intensivsten untersuchte kombinatorische Optimierungsproblem. In diesem Abschnitt wird eine Einf{\"u}hrung in das TSP gegeben. Es werden Problemstellungen erl{\"a}utert, Anwendungen skizziert und einige Schwierigkeiten bei der korrekten Modellierung der Zielfunktion dargelegt. Es ist gar nicht so klar, was in einem konkreten Problem die wirkliche Entfernung ist. Exakte und approximative L{\"o}sungsverfahren werden an Beispielen skizziert, und es wird angedeutet, dass man, obwohl TSPs zu den theoretisch schweren Problemen z{\"a}hlen, in der Praxis TSPs von atemberaubender Gr{\"o}ße l{\"o}sen kann.}, language = {de} } @misc{AchterbergGroetschelKoch, author = {Achterberg, Tobias and Gr{\"o}tschel, Martin and Koch, Thorsten}, title = {Software for Teaching Modeling of Integer Programming Problems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9176}, number = {06-23}, abstract = {Modern applications of mathematical programming must take into account a multitude of technical details, business demands, and legal requirements. Teaching the mathematical modeling of such issues and their interrelations requires real-world examples that are well beyond the toy sizes that can be tackled with the student editions of most commercial software packages. We present a new tool, which is freely available for academic use including complete source code. It consists of an algebraic modeling language and a linear mixed integer programming solver. The performance and features of the tool are in the range of current state-of-the-art commercial tools, though not in all aspects as good as the best ones. Our tool does allow the execution and analysis of large real-world instances in the classroom and can therefore enhance the teaching of problem solving issues. Teaching experience has been gathered and practical usability was tested in classes at several universities and a two week intensive block course at TU Berlin. The feedback from students and teachers has been very positive.}, language = {en} } @misc{GroetschelLoebelVoelker, author = {Gr{\"o}tschel, Martin and L{\"o}bel, Andreas and V{\"o}lker, Manfred}, title = {Optimierung des Fahrzeugumlaufs im {\"O}ffentlichen Nahverkehr}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2195}, number = {SC-96-08}, abstract = {This paper addresses the problem of scheduling vehicles in a public mass transportation system. We show how this problem can be modelled as a special multicommodity flow problem and outline the solution methodology we have developed. Based on polyhedral investigations, we have designed and implemented a branch\&cut algorithm and various heuristics with which real vehicle scheduling problems of truely large scale can be solved to optimality. We describe some implementation issues and report computational results.}, language = {de} } @misc{GroetschelLueggerSperber, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {DMV-Vorhaben. "Verbesserung des benutzerorientierten Zugriffs auf fachspezifische Online-Datenbanken und CD-ROM f{\"u}r Mathematische Institute der Bundesrepublik Deutschland"}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5318}, number = {TR-96-02}, abstract = {Der Report analysiert die Ergebnisse des Projektes ,,Verbesserung des benutzerorientierten Zugriffs auf fachspezifische Online und CD-ROM Datenbanken f{\"u}r Mathematische Institute der Bundesrepublik Deutschland'' der Deutschen Mathematiker-Vereinigung. An dem Projekt, das vom ZIB geleitet und koordiniert worden ist, haben mehr als 50 mathematische Fachbereiche und Forschungsinstitute teilgenommen. Dieses vom damaligen BMFT (einem Teil des jetzigen Bundesministeriums f{\"u}r Bildung, Wissenschaft, Forschung und Technologie) gef{\"o}rderte Projekt hat wesentlich dazu beigetragen, dass fachspezifische Datenbanken heute in den mathematischen Fachbereichen in Deutschland zu den selbstverst{\"a}ndlichen Arbeitsmitteln geh{\"o}ren. Dar{\"u}ber hinaus hat das Projekt die Grundlagen f{\"u}r eine moderne elektronische Informations- und Kommunikationsstruktur in den mathematischen Fachbereichen gelegt.}, language = {de} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Neue Produkte f{\"u}r die digitale Bibliothek: die Rolle der Wissenschaften}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5343}, number = {TR-96-05}, abstract = {Der Artikel ist die ausgearbeitete und erweiterte Fassung eines eingeladenen Vortrags der Tagung ,,Die unendliche Bibliothek - Digitale Information in Wissenschaft, Verlag und Bibliothek''. Dieses Treffen, eine Veranstaltung des B{\"o}rsenvereins des Deutschen Buchhandels e.V., der Deutschen Bibliothek und der Bundesvereinigung Deutscher Bibliothkesverb{\"a}nde, fand im Dezember 1995 in Bonn als Beitrag zur der heute aktuellen Debatte unter Wissenschaftlern, Verlegern, Buchh{\"a}ndlern, Bibliothekaren und Politikern statt, wie unser Wissen und unsere Informationen digital transferiert werden k{\"o}nnen. Der Vortrag stellte das zentrale Problem des heutigen wissenschaftlichen Informationswesens dar, die gleichzeitige Existenz von Informationsflut und Informationsmangel. Nach einer knappen Bestimmung der Ver{\"a}nderung der Kommunikationsstrukturen in den Wissenschaften fragte er nach den essentiellen Ver{\"a}nderungen der Informationsarten, d.h. nach der Natur der kommenden Globalen Digitalen Bibliothek, die als ein {\"u}ber die ganze Welt und auf viele Institutionen verteilter globaler Speicher gesehen wird. Der Vortrag diskutierte zum Schluss die Bed{\"u}rfnisse und Interessen der Wissenschaften und ihre spezifische Verantwortung beim {\"U}bergang in die elektronische Welt. Der Tagungsband ist erschienen beim Harrassowitz Verlag, Wiesbaden, 1996.}, language = {de} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Wissenschaftliche Information und Kommunikation im Umbruch}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5365}, number = {TR-96-07}, abstract = {Steht uns das Ende des traditionellen wissenschaftlichen Publizierens bevor? Neue Technologien er{\"o}ffnen neue Chancen zur Bew{\"a}ltigung der Informationsflut und des gleichzeitigen Informationsmangels. Doch der Einsatz von Technik allein reicht nicht aus.}, language = {de} } @misc{GroetschelKrumkeRambau, author = {Gr{\"o}tschel, Martin and Krumke, Sven and Rambau, J{\"o}rg}, title = {Wo bleibt der Aufzug?}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4175}, number = {SC-99-29}, abstract = {Dieser Artikel gibt eine allgemeinverst{\"a}ndliche Einf{\"u}hrung in die spezielle Problematik kombinatorischer Online-Problem am Beispiel der Fahrstuhlsteuerung.}, language = {de} } @misc{AscheuerFischettiGroetschel, author = {Ascheuer, Norbert and Fischetti, Matteo and Gr{\"o}tschel, Martin}, title = {Solving the Asymmetric Travelling Salesman Problem with Time Windows by Branch-and-Cut}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4191}, number = {SC-99-31}, abstract = {Many optimization problems have several equivalent mathematical models. It is often not apparent which of these models is most suitable for practical computation, in particular, when a certain application with a specific range of instance sizes is in focus. Our paper addresses the Asymmetric Travelling Salesman Problem with time windows (ATSP-TW) from such a point of view. The real--world application we aim at is the control of a stacker crane in a warehouse. We have implemented codes based on three alternative integer programming formulations of the ATSP-TW and more than ten heuristics. Computational results for real-world instances with up to 233 nodes are reported, showing that a new model presented in a companion paper outperforms the other two models we considered --- at least for our special application --- and that the heuristics provide acceptable solutions.}, language = {en} } @misc{BorndoerferGroetschelLoebel, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and L{\"o}bel, Andreas}, title = {Der Schnellste Weg zum Ziel}, doi = {10.1007/978-3-322-96366-6_5}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4209}, number = {SC-99-32}, abstract = {Wir geben eine Einf{\"u}hrung in die Mathematik von und mit Wegen. Nicht auf dem k{\"u}rzesten, aber auf einem hoffentlich kurzweiligen Weg!}, language = {de} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Verkehrsplanung: Bessere L{\"o}sungen mit Mathematik}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4439}, number = {SC-99-54}, abstract = {Anwendungen der Mathematik in der Verkehrs- und Transporttechnologie haben eine große und bedeutende Tradition. Nat{\"u}rlich wurden die ersten Fahrzeuge mit der ingenieurm{\"a}ßigen Methode von Versuch, Irrtum und Verbesserung entworfen. Aber schon sehr bald kamen mathematische Berechnungen hinzu, mit denen mechanische Eigenschaften von Fahrzeugteilen ermittelt und zum Teil optimiert wurden. Die hierzu erforderliche Mathematik wurde in diesem Jahrhundert zu einem m{\"a}chtigen Werkzeugkasten ausgebaut. Mit diesem kann man heute z.B. hocheffiziente Motoren mit geringem Schadstoffausstoß entwerfen, aerodynamisch g{\"u}nstige Fahrzeugprofile ermitteln und Flugzeugfl{\"u}gel berechnen, die die gew{\"u}nschte Last sicher und mit geringem Treibstoffaufwand tragen. Die Mathematik unterst{\"u}tzt die Technologie des Verkehrs beginnend bei globalen Designfragen bis hin zur Spezifizierung von Materialeigenschaften kleinster Bauteile; sie berechnet mit hoher Pr{\"a}zision energieoptimale Bahnen von Raumflugk{\"o}rpern oder zeitoptimale Trajektorien f{\"u}r Flugzeuge, steuert automatische Roboteranlagen oder innerbetriebliche Transportsysteme.}, language = {de} } @misc{GroetschelLueggerSperber, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Elektronische Fachinformation im Bereich der Mathematik an Hochschulen und Statusbericht zum DMV-Projekt. "Fachinformation".}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4910}, number = {TR-92-06}, abstract = {Im Bereich der Mathematik entwickelte sich in Deutschland die elektronische Fachinformation in Form der Online-Datenbank MATH und der CD-ROM CompactMATH auf der Grundlage der Arbeiten des Referateorgans "Zentralblatt f{\"u}r Mathematik und Ihre Grenzgebiete". Das "Zentralblatt" fand weithin Anerkennung und Verbreitung. Die Rezeption elektronischer Fachinformation ging jedoch - nicht nur im Bereich der Mathematik - nur z{\"o}gerlich vonstatten. Die Gr{\"u}nde daf{\"u}r werden in einer vom Bundesminister f{\"u}r Forschung und Technologie (BMFT) initiierten Studie analysiert. Ein k{\"u}rzlich von der Deutschen Mathematiker - Vereinigung begonnenes und vom BMFT gef{\"o}rdertes Vorhaben hat die "Verbesserung des benutzerorientierten Zugriffs auf fachspezifische Online-Datenbanken und CD-ROM f{\"u}r Mathematische Institute in der Bundesrepublik Deutschland" zum Ziel. Insgesamt 51 mathematische Fachbereiche und Institute nehmen daran teil. Elektronische Fachinformation soll zu einem festen Bestandteil des methodischen Instrumentariums der wissenschaftlichen Arbeit werden. Diese Schrift soll die Ausgangslage in den Fachbereichen darstellen und die organisatorischen und technischen Infrastrukturmaßnahmen erl{\"a}utern, mit denen den spezifischen Nutzungshemmnissen begegnet werden soll.}, language = {de} } @misc{BorndoerferGroetschelKlostermeieretal., author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Klostermeier, Fridolin and K{\"u}ttner, Christian}, title = {Telebus-Disposition: Ein Konzept zur Serviceverbesserung bei gleichzeitiger Kostensenkung.[nur hausintern]}, number = {TR-93-03}, abstract = {"`Telebus"' ist der soziale Behindertenfahrdienst im Land Berlin. Das Telebus-Forschungsprojekt des Konrad-Zuse-Zentrums f{\"u}r Informationstechnik (ZIB) hat das Ziel, den Fahrdienst (insbesondere die Disposition der Telebusse) zu verbessern, d.h. kundenfreundlicher zu gestalten und gleichzeitig billiger zu machen. In diesem Bericht werden die bisherigen Ergebnisse dargestellt und weitere M{\"o}glichkeiten zur Verbesserung des Service und zur Reduzierung der Kosten skizziert. \originalTeX}, language = {de} } @misc{GroetschelLueggerSperber, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Wissenschaftliches Publizieren und Elektronische Fachinformation im Umbruch: ein Situationsbericht aus der Sicht der Mathematik.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4966}, number = {TR-93-04}, abstract = {In diesem Aufsatz geben wir einen Bericht {\"u}ber den Stand der elektronischen Fachinformation in der Mathematik in Deutschland. Wir sehen diesen Bereich nicht als ein organisatorisch isoliertes Unterfangen, sondern eingebettet in weltweite Bestrebungen und Entwicklungen in der Informationstechnik, im wissenschaftlichen Publikationswesen und nat{\"u}rlich auch in der Mathematik selber. Unser Artikel endet mit einigen weitreichenden (und einigen Lesern m{\"o}glicherweise spektakul{\"a}r erscheinenden) Vorschl{\"a}gen, die sowohl die Informationsanbieter (wie die Fachinformationszentren und Verlage), die {\"o}ffentlichen Geldgeber als auch die mathematischen Organisationen (wie z.~B.~ die DMV und die mathematischen Fachbereiche) betreffen. Um den gegenw{\"a}rtigen Zustand der elektronischen Fachinformation und unsere Gedanken zu diesem Thema ad{\"a}quat beschreiben zu k{\"o}nnen, pr{\"a}sentieren wir eine breit angelegte Situationsanalyse. Wir stellen den gegenw{\"a}rtigen Stand der technologischen Entwicklung im elektronischen Publizieren dar und skizzieren seine Auswirkungen. Wir beschreiben das Feld der Interessen und Kr{\"a}fte im Bereich des mathematischen Publizierens. Wir geben einen kurzen historischen Abriss der Geschichte der Klassifikation und des Referatewesens und zeigen, wie dieses in die elektronische Fachinformation auf dem Gebiet der Mathematik m{\"u}ndete und dann zum DMV-Projekt Fachinformation f{\"u}hrte, das der Anlass zur Abfassung dieses Artikels war. Wir skizzieren die gegenw{\"a}rtige Rezeption elektronischer Fachinformation in der Mathematik in Deutschland. Ausgehend von einer Darstellung und Bewertung verschiedener Modelle des Referatewesens zeigen wir unter Einbeziehung der vorhandenen technischen Gegebenheiten (elektronische Netze etc.) verschiedene M{\"o}glichkeiten zur Liberalisierung und Rationalisierung des weltweiten mathematischen Informationswesens auf. Wir sehen den Austausch von Information in engem Zusammenhang mit dem Austausch von Software im Wissenschaftsbereich und regen auch in diesem Bereich an, internationale Kooperation und Offenheit anzustreben. \originalTeX}, language = {de} } @misc{DalitzGroetschelLueggeretal., author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Verteiltes Informationssystem f{\"u}r die Mathematik}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5218}, number = {TR-95-06}, abstract = {``Das System ist zerbrochen!'', so lautet das Urteil von Keith Dennis, Professor an der Cornell University und neuer Verantwortlicher f{\"u}r die Mathematical Reviews, {\"u}ber das traditionelle Publikationswesen in der Mathematik. Was sind die Ursachen? Haupts{\"a}chlich sind es das starke Wachstum der mathematischen Literatur, die langen Verz{\"o}gerungen von der Erstellung bis zum Erscheinen einer Arbeit, die hohen Ablehnungsraten bei mathematischen Journalen aufgrund beschr{\"a}nkter Seitenzahlen (und nicht wegen mangelnder Qualit{\"a}t) sowie drastisch steigende Preise f{\"u}r Zeitschriften und B{\"u}cher bei gleichzeitiger Reduktion der Bibliotheksetats.}, language = {de} } @misc{DalitzGroetschelLueggeretal., author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Distributed Information System for Mathematics (Available only in german, TR 95-06)}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5225}, number = {TR-95-07}, abstract = {"The system is broken'' is how Keith Dennis, professor at Cornell University and the new editor-in-chief of the Mathematical Reviews characterizes the traditional ways and means of publication in mathematics. What are the reasons? The main reasons are the extreme growth in the mathematical literature, the long delays between preparation and publication of an article, the high number of rejected papers due to page limitations (not lack of quality) as well as drastic price increases for journals and books with library budgets being reduced at the same time.}, language = {en} } @misc{GroetschelLueggerZimmermann, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Zimmermann, Uwe}, title = {Wissenschaftliche Information am Wendepunkt? Zw{\"a}nge, Krisen und Chancen aus Sicht der Mathematik}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5239}, number = {TR-95-08}, language = {de} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Aufbau elektronischer Informations- und Kommunikationsstrukturen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5252}, number = {TR-95-10}, abstract = {Die vorliegende Arbeit ist die (z.T.~wesentlich) erweiterte Fassung eines Vortrages auf dem Deutschen Dokumentartag im September 1995 an der Fachhochschule Potsdam. Unser Ziel ist eine Bestandsaufnahme der gegenw{\"a}rtigen Entwicklungen auf dem Gebiet der elektronischen Information und Kommunikation. Wir diskutieren Chancen und Risiken, beleuchten gesellschaftliche Rahmenbedingungen - vor allem im Vergleich mit den Vereinigten Staaten von Amerika - und skizzieren Aufgaben im Bereich von Forschung, Staat und Wirtschaft, die unserer Meinung nach noch zu bew{\"a}ltigen sind. Wir f{\"u}hren insbesondere in Gebiete ein, die vermutlich in naher Zukunft die Landschaft des Dokumentierens und Archivierens wesentlich ver{\"a}ndern werden. Wir benutzen dabei h{\"a}ufig Beispiele und Modellvorstellungen aus der Mathematik, unserem eigenen Fachgebiet, die u.a. zeigen, wie Elemente des Informierens, Dokumentierens und Archivierens durch die neuen Technologien der elektronischen Datenverarbeitung und Kommunikation ineinander flie\"sen. Mehr Leistung kann mit geringeren Kosten erzielt werden. Wir schliessen mit einer Auflistung von neuen Perspektiven und M{\"o}glichkeiten zum Handeln in diesem Bereich.}, language = {de} } @misc{DalitzGroetschelLueggeretal., author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {Neue Perspektiven eines verteilten Informationssystems f{\"u}r die Mathematik.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5122}, number = {TR-94-07}, abstract = {Die Kombination von elektronischer Fachinformation mit den neuen Mitteln der Kommunikation er{\"o}ffnet neue Perspektiven f{\"u}r die Mathematik in Deutschland. Aufbauend auf das laufende, BMFT-gef{\"o}rderte Projekt ``Fachinformation'' der Deutschen Mathematiker-Vereinigung (DMV) plant die DMV eine Querschnittsaktivit{\"a}t f{\"u}r die Mathematik. Diese soll nicht nur die mathematischen Fachbereiche und Forschungsinstitute einbeziehen, sondern auch mathematische Forschungslabors aus der Industrie und die Informationsversorger der Mathematik, insbesondere die wissenschaftlichen Verlage, die TIB Hannover, die Bibliotheken der Universit{\"a}ten und \mbox{-- nicht zuletzt --} das FIZ Karlsruhe mit dem Zentralblatt f{\"u}r Mathematik. \noindent Auf der technischen Grundlage des Internet und seiner weltweit verbreiteten Informationsdienste (Gopher, WAIS, WorldWideWeb, Hyper-G, ftp und E-mail) soll ein verteiltes, mathematisches Informationssystem geschaffen werden, bei dem die Partner des gemeinsamen Vorhabens ihre {\"o}rtlichen Ressourcen untereinander und zugleich weltweit verf{\"u}gbar machen. Diese Ziele sind durch konsequenten Einsatz von Software erreichbar, die nach dem Client-Server-Modell strukturiert und die im Internet verbreitet bzw.~anerkannt ist. \noindent Die Bereitstellung von Technik reicht keineswegs aus. Ohne die Schaffung einer personellen, organisatorischen und technischen Infrastruktur ist die Durchf{\"u}hrung eines solchen Projekts nicht m{\"o}glich. Als Massnahmen sind - f{\"u}r alle Partner - geplant: \hspace*{2mm} * Schaffung der Funktion des Informationsbeauftragten \hspace*{2mm} * Einrichtung eines gemeinsamen ``Forums f{\"u}r mathematische Information'' \hspace*{2mm} * Errichtung und Betreuung von mathematischen Informationsstationen \hspace*{2mm} * Teilnahme an nationalen und internationalen Standardisierungsmassnahmen \hspace*{2mm} * Workshops und regelm{\"a}ssige Schulungen, {\"O}ffentlichkeitsarbeit \noindent Als Aktivit{\"a}ten - mit Focus auf mathematische Fachinformation - sind folgende Teilaufgaben und Pilotvorhaben bei allen Partnern geplant: \hspace*{2mm} * Einrichtung von elektronischen Informationssystemen \hspace*{2mm} * Verteiltes elektronisches Angebot von Preprints und Skripten (Volltexte) \hspace*{2mm} * Verteiltes elektronisches Angebot von Software- und Datensammlungen \hspace*{2mm} * Zugriff auf globale Informationssysteme in der Mathematik \hspace*{2mm} * Organisation eines Lebenden Mathematischen Museums \hspace*{2mm} * Zugriff auf elektronische Kataloge von Bibliotheken, insbesondere Fachbereichsbibliotheken \hspace*{2mm} * Schaffung eines organisatorischen Rahmens f{\"u}r elektronische mathematische Journale \hspace*{2mm} * Elektronisches Angebot von eingescannten historischen Dokumenten und B{\"u}chern \hspace*{2mm} * Schaffung einer Organisationsform f{\"u}r elektronisches Reviewing \hspace*{2mm} * Erprobung von Verfahren zur elektronischen Lieferung von Dokumenten \hspace*{2mm} * Elektronische Projektorganisation \noindent Das Vorhaben zielt ab auf die Schaffung einer informationstechnischen Infrastruktur f{\"u}r Datenbank-Retrieval, E-mail, ``Electronic Conferencing'' und fachspezifische Informationsnetze in exemplarischer Form f{\"u}r Wissenschaft und Industrie - auch f{\"u}r andere Fachgebiete.}, language = {de} } @misc{DalitzGroetschelLueggeretal., author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and L{\"u}gger, Joachim and Sperber, Wolfram}, title = {New Perspectives of a Distributed Information System for Mathematics.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5139}, number = {TR-94-08}, abstract = {\begin{footnotesize} \noindent Combining electronic specialized information, such as electronic information retrieval from central databases, with the new means of communication opens up new perspectives for mathematics in Germany. Based on the current Fachinformationsprojekt (Specialized Information Project) run by the Deutsche Mathematiker-Vereinigung (DMV) and supported by the Federal Minister for Research and Technology (BMFT), the DMV is planning a new infrastructure activity for mathematics. This activity will not only include mathematical university departments and research institutes, but also partners from mathematical research laboratories in industry as well as suppliers of mathematical information, in particular, scientific publishing houses, the Technical Information Library (TIB) Hannover, university libraries and -- last but not least -- the Fachinformationszentrum (FIZ) Karlsruhe with the Zentralblatt f{\"u}r Mathematik. \noindent On the technical basis of the Internet and its worldwide information services (Gopher, WAIS, World Wide Web, Hyper-G, ftp and e-mail), a distributed mathematical information system is to be created, whose partners make their local resources available both to other partners and to the worldwide Internet community. These aims can be achieved by means of the consequent use of software that is structured according to the client-server model and distributed and accepted within the Internet. \noindent Providing the technical equipment, however, is by far not enough. Without the creation of a personal, technical and organizational infrastructure, realization of such a project will not be possible. For every partner the realization of the following measures is envisaged:\\[-7mm] \noindent \end{footnotesize} \begin{small} \begin{itemize} \item[*] Establishing an Information Coordinator\/ at every participating institution\\[-8mm] \item[*] Creation of a Forum for Mathematical Information\/\\[-8mm] \item[*] Installation and maintenance of Mathematical Information Stations\/\\[-8mm] \item[*] Participation in national and international Standardization Activities\/\\[-8mm] \item[*] Regular workshops and training courses, public relations\\[-7mm] \end{itemize} \noindent The following activities (carried out by all partners or within pilot projects by special groups) focusing on mathematical and mathematics-related information are planned:\\[-7mm] \noindent \begin{itemize} \item[*] Set up of Electronic Information Systems\/ by all partners \\[-8mm] \item[*] Distributed\/ electronic offer of Preprints\/ and scripts (full texts) by all partners\\[-8mm] \item[*] Distributed\/ electronic offer of Software and Data Collections\/ by all partners\\[-8mm] \item[*] Access to Global Information Systems in Mathematics\/\\[-8mm] \item[*] Organization of a Living Museum of Mathematics\/\\[-8mm] \item[*] Access to {\it Electronic Library Catalogs,}\/ esp.~to libraries of university departments\\[-8mm] \item[*] Electronic offer of Scanned Historical Books and Documents\/\\[-8mm] \item[*] Creation and management of Electronic Mathematical Journals\/\\[-8mm] \item[*] Creation of a framework for various kinds of Electronic Reviewing\/\\[-8mm] \item[*] Testing of new methods for Electronic Document Delivery\/\\[-8mm] \item[*] Electronic Project Organization\/\\[-7mm] \end{itemize} \noindent \end{small} \begin{footnotesize} The project aims, at its beginning, at the creation of an information infrastructure for database retrieval, e-mail, electronic conferencing and subject-specific information networks. Its focus is on mathematics in Germany. The general scope, however, is broader. The project is open for discussion, coordination, and cooperation with partners in other areas of science, industry or in other countries. It is also hoped that this project may form an example along which other models of electronic information and communication can be developed. Moreover, the project is also meant to enhance the offer from German mathematics to the worldwide "give and take" within the Internet community. \end{footnotesize}}, language = {en} } @misc{GroetschelLuegger, author = {Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Wissenschaftliche Kommunikation am Wendepunkt - Bibliotheken im Zeitalter globaler elektronischer Netze -}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5164}, number = {TR-95-01}, abstract = {Durch extrem steigende Preise f{\"u}r traditionelle wissenschaftliche Zeitschriften bei gleichzeitiger Stagnation der Bibliotheksetats an den Hochschulen und bei weltweit weiterhin anwachsenden Forschungsleistungen ist die ad{\"a}quate Versorgung der Wissenschaften mit relevanter Literatur gef{\"a}hrdet. Dokumentenliefersysteme werden vielerorts als L{\"o}sung dieser ``Bibliothekskrise'' propagiert. Dieser Weg ist f{\"u}r den derzeitigen Literaturversorgungsmarkt sinnvoll, aber er bietet keine langfristig stabile L{\"o}sung. Wenn die Grundversorgung der Bibliotheken weiter schrumpft, wird Dokumentenlieferung in der zur Zeit {\"u}blichen bzw. geplanten Form die Kosten nur noch zus{\"a}tzlich in die H{\"o}he treiben. Wir pl{\"a}dieren in diesem Aufsatz f{\"u}r einen grunds{\"a}tzlich neuen Ansatz. Wir sind der Meinung, da\ss{} einzig der {\"U}bergang auf elektronische Medien eine bezahlbare, umfassende und benutzerfreundliche Versorgung der Wissenschaftler mit Literatur sichern kann. Wir zeigen -- unter anderem anhand elektronischer Zeitschriften -- wie zum Beispiel durch Kooperation von Bibliotheken mit Fachbereichen und wissenschaftlichen Gesellschaften neue Wege der Informationsversorgung beschritten werden k{\"o}nnen. Dieser Vorschlag einer neuen Organisation des wissenschaftlichen Publikationswesen erfordert Umdenken in vielen Bereichen. Neue Organisationsformen sind erforderlich, Rechte m{\"u}ssen anders verteilt, Aufgaben auf andere Schultern geladen werden. Die Bibliotheken werden besonders betroffen sein. Aber f{\"u}r sie ist die konsequente Nutzung der sich rasch ausbreitenden Informationstechnik (darunter verstehen wir u. a. globale elektronische Netze, leistungsf{\"a}hige Rechner, kosteng{\"u}nstige Speichermedien, benutzerfreundliche Such- und Retrieval-Systeme, Entwicklung weltweit akzeptierter Datenformate) eine wirkliche und m{\"o}glicherweise die einzige Chance, ihrem Auftrag zur umfassenden Versorgung der Wissenschaften mit Literatur zu gesamtwirtschaftlich niedrigen Kosten weiterhin nachzukommen. Au\ss{}erdem bietet die Bereitstellung und Archivierung wissenschaftlicher Literatur auf elektronischem Wege bedeutende Vorteile gegen{\"u}ber der traditionellen Dokumentation auf Papier, die im {\"u}brigen, falls erw{\"u}nscht, weiterhin betrieben werden kann.}, language = {de} } @misc{BorndoerferGroetschelLoebel, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and L{\"o}bel, Andreas}, title = {Alcuin's Transportation Problems and Integer Programming}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1932}, number = {SC-95-27}, abstract = {The need to solve {\it transportation problems\/} was and still is one of the driving forces behind the development of the mathematical disciplines of graph theory, optimization, and operations research. Transportation problems seem to occur for the first time in the literature in the form of the four ''River Crossing Problems'' in the book Propositiones ad acuendos iuvenes. The {\it Propositiones\/} ---the oldest collection of mathematical problems written in Latin--- date back to the \$8\$th century A.D. and are attributed to Alcuin of York, one of the leading scholars of his time, a royal advisor to Charlemagne at his Frankish court. Alcuin's river crossing problems had no impact on the development of mathematics. However, they already display all the characteristics of today's large-scale real transportation problems. From our point of view, they could have been the starting point of combinatorics, optimization, and operations research. We show the potential of Alcuin's problems in this respect by investigating his problem~18 about a wolf, a goat and a bunch of cabbages with current mathematical methods. This way, we also provide the reader with a leisurely introduction into the modern theory of integer programming.}, language = {en} } @misc{AscheuerGroetschelKrumkeetal., author = {Ascheuer, Norbert and Gr{\"o}tschel, Martin and Krumke, Sven and Rambau, J{\"o}rg}, title = {Combinatorial Online Optimization}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3674}, number = {SC-98-24}, abstract = {In ``classical'' optimization, all data of a problem instance are considered given. The standard theory and the usual algorithmic techniques apply to such cases only. Online optimization is different. Many decisions have to be made before all data are available. In addition, decisions once made cannot be changed. How should one act ``best'' in such an environment? In this paper we survey online problems coming up in combinatorial optimization. We first outline theoretical concepts, such as competitiveness against various adversaries, to analyze online problems and algorithms. The focus, however, lies on real-world applications. We report, in particular, on theoretical investigations and our practical experience with problems arising in transportation and the automatic handling of material.}, language = {en} } @misc{BorndoerferGroetschelKlostermeieretal., author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Klostermeier, Fridolin and K{\"u}ttner, Christian}, title = {Optimierung des Berliner Behindertenfahrdienstes}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2799}, number = {SC-97-10}, abstract = {In diesem Artikel geben wir einen {\"U}berblick {\"u}ber das Telebus-Projekt am Konrad-Zuse-Zentrum, Berlin, durch das der Behindertenfahrdienst in Berlin reorganisiert und optimiert wurde. Wir berichten kurz {\"u}ber die mathematischen Probleme und, etwas ausf{\"u}hrlicher, {\"u}ber die nicht-mathematischen Schwierigkeiten, die bei der Durchf{\"u}hrung dieses Projektes auftraten.}, language = {de} } @misc{AscheuerFischettiGroetschel, author = {Ascheuer, Norbert and Fischetti, Matteo and Gr{\"o}tschel, Martin}, title = {A polyhedral study of the asymmetric travelling salesman problem with time windows}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2807}, number = {SC-97-11}, abstract = {The asymmetric travelling salesman problem with time windows (ATSP-TW) is a basic model for scheduling and routing applications. In this paper we present a formulation of the problem involving only 0/1-variables associated with the arcs of the underlying digraph. This has the advantage of avoiding additional variables as well as the associated (typically very ineffective) linking constraints. In the formulation, time window restrictions are modelled by means of ``infeasible path elimination'' constraints. We present the basic form of these constraints along with some possible strengthenings. Several other classes of valid inequalities derived from related asymmetric travelling salesman problems are also described, along with a lifting theorem. We also study the ATSP-TW polytope, \$P_{TW}\$, defined as the convex hull of the integer solutions of our model. We show that determining the dimension of \$P_{TW}\$ is strongly {\em NP}--complete problem, even if only one time window is present. In this latter case, we provide a minimal equation system for \$P_{TW}\$. Computational experiments on the new formulation are reported in a companion paper [1997] where we show that it outperforms alternative formulations on some classes of problem instances.}, language = {en} } @misc{GodsilGroetschelWelsh, author = {Godsil, C. D. and Gr{\"o}tschel, Martin and Welsh, D. J. A.}, title = {Combinatorics in Statistical Physics}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-694}, number = {SC-91-19}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {Discrete Mathematics in Manufacturing.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-738}, number = {SC-92-03}, abstract = {Manufacturing is a topic that provides rich opportunities for important mathematical contributions to real-world problems. The purpose of this paper is to show, by means of several examples, where and how mathematical problems of a discrete nature arise in manufacturing and to demonstrate the savings and improvements that can be achieved by employing the techniques of combinatorial optimization. The topics covered range from the design phase of a product (e. g.,routing, placement and via minimization in VLSI design), the control of CNC machines (e. g., drilling and plotting), to the management of assembly lines, storage systems and whole factories. We also point out difficulties in the modelling of complex situations and outline the algorithmic methods that are used for the solution of the mathematical problems arising in manufacturing. {\bf Key words:} discrete mathematics , combinatorial optimization, applications to manufacturing.}, language = {en} } @misc{GroetschelMonmaStoer, author = {Gr{\"o}tschel, Martin and Monma, Clyde and Stoer, Mechthild}, title = {Design of Survivable Networks}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1054}, number = {SC-93-09}, language = {en} } @misc{GroetschelLovasz, author = {Gr{\"o}tschel, Martin and Lov{\´a}sz, L{\´a}szlo}, title = {Combinatorial Optimization.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1098}, number = {SC-93-13}, abstract = {This paper will appear as Chapter 28 of the forthcoming "Handbook on Combinatorics" (editors: R. Graham, M. Gr{\"o}tschel, L. Lovasz) to be published in 1994, by North-Holland.}, language = {en} } @misc{AbdelHamidAscheuerGroetscheletal., author = {Abdel-Hamid, Atef Abdel-Aziz and Ascheuer, Norbert and Gr{\"o}tschel, Martin and Schorer, Herbert}, title = {Simulation und Optimierung einer PC-Fertigung unter Echtzeitbedingungen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1700}, number = {SC-95-04}, abstract = {Die Business Unit PC in Augsburg ist die zentrale Produktionsst{\"a}tte der Siemens--Nixdorf Informationssysteme (SNI) AG f{\"u}r Personal Computer sowie f{\"u}r einige Periph{\"a}rger{\"a}te. Das Werk, entworfen nach modernen CIM/CAI--Konzepten (Computer Integrated Manufacturing/ Computer Aided Industry), wurde 1987 errichtet. Bald zeigte sich jedoch, daß es f{\"u}r ein zu geringes Produktionsvolumen ausgelegt war und einige Komponenten des Systems Engp{\"a}sse im Produktionsbetrieb darstellen. Das Management suchte nach M{\"o}glichkeiten, den Produktionsfluß zu verbessern, ohne teure technische {\"A}nderungen am System vornehmen zu m{\"u}ssen. Eine Forschungsgruppe des Konrad--Zuse--Zentrums f{\"u}r Informationstechnik (die ehemals an der Universit{\"a}t Augsburg ans{\"a}ssig war) analysierte, unterst{\"u}tzt von einigen Studenten und Ingenieuren der SNI, den Produktionsfluß und lokalisierte Schwachstellen. Basierend auf diesen Erkenntnissen wurden mathematische Fragestellungen erarbeitet und auf mathematischen Optimierungsverfahren basierende Softwarepakete entwickelt, die jetzt teilweise bei SNI im Einsatz sind. Im folgenden werden einige dieser Fragestellungen, deren Modellierung und mathematische Behandlung beschrieben. Einige der Ans{\"a}tze, die hier dargestellt werden sollen, sind teilweise schon in Gr{\"o}tschel [Gr{\"o}92] angesprochen worden.}, language = {de} } @misc{GroetschelMonmaStoer, author = {Gr{\"o}tschel, Martin and Monma, Clyde and Stoer, Mechthild}, title = {A Polyhedral Approach to Network Connectivity Problems (Extended Abstract).}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-924}, number = {SC-92-22}, abstract = {We present a polyhedral approach for the general problem of designing a minimum-cost network with specified connectivity requir}, language = {en} } @misc{GroetschelMonmaStoer, author = {Gr{\"o}tschel, Martin and Monma, Clyde and Stoer, Mechthild}, title = {Polyhedral and Computational Investigations for Designing Communication Networks with High Survivability Requirements.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-944}, number = {SC-92-24}, abstract = {We consider the important practical and theoretical problem of designing a low-cost communications network which can survive failures of certain network components. Our initial interest in this area was motivated by the need to design certain ``two-connected" survivable topologies for fiber optic communication networks of interest to the regional telephone companies. In this paper, we describe some polyhedral results for network design problems with higher connectivity requirements. We also report on some preliminary computational results for a cutting plane algorithm for various real-world and random problems with high connectivity requirements which shows promise for providing good solutions to these difficult problems. \def\NP{\$\cal NP\$}}, language = {en} } @misc{GroetschelPadberg, author = {Gr{\"o}tschel, Martin and Padberg, Manfred}, title = {Ulysses 2000: In Search of Optimal Solutions to Hard Combinatorial Problems.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-1296}, number = {SC-93-34}, abstract = {Combinatorial optimization problems pervade many areas of human problem solving especially in the fields of business, economics and engineering. Intensive mathematical research and vast increases in raw computing power have advanced the state of the art in exact and heuristic problem solving at a pace that is unprecedented in human history. We survey here in layman's terms some of the fundamental concepts and principles that have led this progress. (This article will appear -- possibly in modified form -- in a popular science magazine.)}, language = {en} } @misc{AlevrasGroetschelWessaely, author = {Alevras, Dimitris and Gr{\"o}tschel, Martin and Wess{\"a}ly, Roland}, title = {Cost-Efficient Network Synthesis from Leased Lines}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2912}, number = {SC-97-22}, abstract = {Given a communication demand between each pair of nodes of a network we consider the problem of deciding what capacity to install on each edge of the network in order to minimize the building cost of the network and to satisfy the demand between each pair of nodes. The feasible capacities that can be leased from a network provider are of a particular kind in our case. There are a few so-called basic capacities having the property that every basic capacity is an integral multiple of every smaller basic capacity. An edge can be equipped with a capacity only if it is an integer combination of the basic capacities. We treat, in addition, several restrictions on the routings of the demands (length restriction, diversification) and failures of single nodes or single edges. We formulate the problem as a mixed integer linear programming problem and develop a cutting plane algorithm as well as several heuristics to solve it. We report on computational results for real world data.}, language = {en} } @misc{BorndoerferGroetschelKlostermeieretal., author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Klostermeier, Fridolin and K{\"u}ttner, Christian}, title = {Telebus Berlin: Vehicle Scheduling in a Dial-a-Ride System}, doi = {10.1007/978-3-642-85970-0_19}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2925}, number = {SC-97-23}, abstract = {{\em Telebus\/} is Berlin's dial-a-ride system for handicapped people that cannot use the public transportation system. The service is provided by a fleet of about 100 mini-busses and includes aid to get in and out of the vehicle. Telebus has between 1,000 and 1,500 transportation requests per day. The problem arises to schedule these requests into the vehicles such that punctual service is provided while operation costs should be minimum. Additional constraints include pre-rented vehicles, fixed bus driver shift lengths, obligatory breaks, and different vehicle capacities. We use a {\em set partitioning\/} approach for the solution of the bus scheduling problem that consists of two steps. The first {\em clustering\/} step identifies segments of possible bus tours (``orders'') such that more than one person is transported at a time; the aim in this step is to reduce the size of the problem and to make use of larger vehicle capacities. The problem to select a set of orders such that the traveling distance of the vehicles within the orders is minimal is a set partitioning problem that we can solve to optimality. In the second step the selected orders are {\em chained\/} to yield possible bus tours respecting all side constraints. The problem to select a set of such bus tours such that each order is serviced once and the total traveling distance of the vehicles is minimum is again a set partitioning problem that we solve approximately. We have developed a computer system for the solution of the bus scheduling problem that includes a branch-and-cut algorithm for the solution of the set partitioning problems. A version of this system is in operation at Telebus since July 1995. Its use made it possible that Telebus can service today about 30\\% more requests per day for the same amount of money than before.}, language = {en} } @misc{AlevrasGroetschelWessaely, author = {Alevras, Dimitris and Gr{\"o}tschel, Martin and Wess{\"a}ly, Roland}, title = {Capacity and Survivability Models for Telecommunication Networks}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2931}, number = {SC-97-24}, abstract = {Designing low-cost networks that survive certain failure situations is one of the prime tasks in the telecommunication industry. In this paper we survey the development of models for network survivability used in practice in the last ten years. We show how algorithms integrating polyhedral combinatorics, linear programming, and various heuristic ideas can help solve real-world network dimensioning instances to optimality or within reasonable quality guarantees in acceptable running times. The most general problem type we address is the following. Let a communication demand between each pair of nodes of a telecommunication network be given. We consider the problem of choosing, among a discrete set of possible capacities, which capacity to install on each of the possible edges of the network in order to (i) satisfy all demands, (ii) minimize the building cost of the network. \noindent In addition to determining the network topology and the edge capacities we have to provide, for each demand, a routing such that (iii) no path can carry more than a given percentage of the demand, (iv) no path in the routing exceeds a given length. \noindent We also have to make sure that (v) for every single node or edge failure, a certain percentage of the demand is reroutable. \noindent Moreover, for all failure situations feasible routings must be computed. The model described above has been developed in cooperation with a German mobile phone provider. We present a mixed-integer programming formulation of this model and computational results with data from practice.}, language = {en} } @misc{DalitzGroetschelLuegger, author = {Dalitz, Wolfgang and Gr{\"o}tschel, Martin and L{\"u}gger, Joachim}, title = {Information Services for Mathematics in the Internet (Math-Net)}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2949}, number = {SC-97-25}, abstract = {The present paper gives a brief description of the Math-Net project which is carried out by nine mathematical institutions in Germany, supported by Deutsches Forschungsnetz (DFN) and Deutsche Telekom. The project aims at setting up the technical and organizational infrastructure for efficient, inexpensive and user-driven information services for mathematics. With the aid of active (structured retrieval mechanisms) and passive (profile services) components, electronic mathematical information in Germany will be made available to the scientist at his workplace. The emphasis is put on information about publications, software and data collections, teaching and research activities, but also on organizational and bibliographical information. Decentral organization structures, distributed search systems as well as the use of meta-information (metadata) in accordance with the Dublin Core (hopefully) guarantee a longterm, high-quality repository of data. The well-known mathematical software and data collection netlib\/ will be used as an example to illustrate how such a collection can be adapted to Math-Net. An integration of netlib into HyperWave offers additional perspectives and functionalities.}, language = {en} } @misc{AbdelHamidAscheuerGroetschel, author = {Abdel-Hamid, Atef Abdel-Aziz and Ascheuer, Norbert and Gr{\"o}tschel, Martin}, title = {Order Picking in an Automatic Warehouse: Solving Online Asymmetric TSPs}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3519}, number = {SC-98-08}, abstract = {We report on a joint project with industry that had the aim to sequence transportation requests within an automatic storage system in such a way that the overall travel time is minimized. The manufacturing environment is such that scheduling decisions have to be made before all jobs are known. We have modeled this task as an \emph{online} Asymmetric Traveling Salesman Problem (ATSP). Several heuristics for the online ATSP are compared computationally within a simulation environment to judge which should be used in practice. Compared to the priority rule used so far, the optimization package reduced the unloaded travel time by about 40~\\%. Because of these significant savings our procedure was implemented as part of the control software for the stacker cranes of the storage systems.}, language = {en} } @misc{BorndoerferGroetschelLoebel, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and L{\"o}bel, Andreas}, title = {Optimization of Transportation Systems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3529}, number = {SC-98-09}, abstract = {The world has experienced two hundred years of unprecedented advances in vehicle technology, transport system development, and traffic network extension. Technical progress continues but seems to have reached some limits. Congestion, pollution, and increasing costs have created, in some parts of the world, a climate of hostility against transportation technology. Mobility, however, is still increasing. What can be done? There is no panacea. Interdisciplinary cooperation is necessary, and we are going to argue in this paper that {\em Mathematics\/} can contribute significantly to the solution of some of the problems. We propose to employ methods developed in the {\em Theory of Optimization\/} to make better use of resources and existing technology. One way of optimization is better planning. We will point out that {\em Discrete Mathematics\/} provides a suitable framework for planning decisions within transportation systems. The mathematical approach leads to a better understanding of problems. Precise and quantitative models, and advanced mathematical tools allow for provable and reproducible conclusions. Modern computing equipment is suited to put such methods into practice. At present, mathematical methods contribute, in particular, to the solution of various problems of {\em operational planning}. We report about encouraging {\em results\/} achieved so far.}, language = {en} } @misc{BleyGroetschelWessaely, author = {Bley, Andreas and Gr{\"o}tschel, Martin and Wess{\"a}ly, Roland}, title = {Design of Broadband Virtual Private Networks: Model and Heuristics for the B-WiN}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3565}, number = {SC-98-13}, abstract = {We investigate the problem of designing survivable broadband virtual private networks that employ the Open Shortest Path First (OSPF) routing protocol to route the packages. The capacities available for the links of the network are a minimal capacity plus multiples of a unit capacity. Given the directed communication demands between all pairs of nodes, we wish to select the capacities in a such way, that even in case of a single node or a single link failure a specified percentage of each demand can be satisfied and the costs for these capacities are minimal. We present a mixed--integer linear programming formulation of this problem and several heuristics for its solution. Furthermore, we report on computational results with real-world data.}, language = {en} } @misc{BorndoerferGroetschelHerzogetal., author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Herzog, Werner and Klostermeier, Fridolin and Konsek, Wilhelm and K{\"u}ttner, Christian}, title = {K{\"u}rzen muß nicht Kahlschlag heißen - das Beispiel Telebus-Behindertenfahrdienst Berlin}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2510}, number = {SC-96-41}, abstract = {M{\"u}ssen Etatk{\"u}rzungen bei staatlichen Dienstleistungseinrichtungen notwendig zu Leistungseinschr{\"a}nkungen oder Geb{\"u}hrenerh{\"o}hungen f{\"u}hren? Wir zeigen am Beispiel des Berliner Behindertenfahrdienstes {\em Telebus}, da\ss{} Sparzwang auch als Chance zur Verbesserung der eigenen Verwaltungs- und Arbeitsabl{\"a}ufe genutzt werden kann. Durch st{\"a}rkere Dienstleistungsorientierung, Vereinfachung der Arbeitsabl{\"a}ufe und durch den Einsatz von moderner EDV und von mathematischen Optimierungsmethoden zur Fahrzeugeinsatzplanung werden bei Telebus heute staatliche Leistungen trotz geringeren Etats besser erbracht als vorher.}, language = {de} } @misc{AlevrasGroetschelJonasetal., author = {Alevras, Dimitris and Gr{\"o}tschel, Martin and Jonas, Peter and Paul, Ulrich and Wess{\"a}ly, Roland}, title = {Survivable Mobile Phone Architectures: Models and Solution Methods}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2582}, number = {SC-96-48}, abstract = {In the highly competitive area of telecommunications, cost, quality, and network management are among the most important aspects to be considered when designing a network. We study the problem of dimensioning a telecommunication network that is still operating in case of a failure of a network component. Given a demand between each pair of nodes of a telecommunication network and a finite set of possible capacities for each edge of the network, we consider the problem of deciding what capacity to install on each edge of the network in order to minimize the building cost of the network and to satisfy the demand between each pair of nodes, even if a network component fails. The routing of the demands must satisfy the following additional restrictions: (a) there is a maximum number of nodes allowed in each path between any pair of nodes (path length restriction), and (b) there is a maximum percentage of the demand between each pair of nodes that can be routed through any network component (diversification restriction). Moreover, the chosen capacities must be such that, for every single node or single edge failure, a certain percentage of the demand between any pair of nodes is reroutable (i.e. it ``survives'' the particular failure). We formulate the problem as a mixed integer linear programming problem and present a cutting plane algorithm as well as several heuristics for its solution. Furthermore, we discuss several ways to implement survivability into a telecommunication network.}, language = {en} } @misc{AlevrasGroetschelWessaely, author = {Alevras, Dimitris and Gr{\"o}tschel, Martin and Wess{\"a}ly, Roland}, title = {A Network Dimensioning Tool}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2591}, number = {SC-96-49}, abstract = {Designing low cost networks that survive certain failure situations belongs to one of the prime tasks in the telecommunications industry. In this paper we describe a mathematical model combining several aspects of survivability that are elsewhere treated in a hierarchical fashion. We present mathematical investigations of this integrated model, a cutting plane algorithm, as well as several heuristics for its solution. Moreover, we report computational results with real world data. The problem we address is the following. Suppose, between each pair of nodes in a region, a communication demand is given. We want to determine the topology of a telecommunication network connecting the given nodes and to dimension all potential physical links. For each link, the possible capacities are restricted to a given finite set. The capacities must be chosen such that the communication demands are satisfied, even if certain network components fail, and such that the network building costs are as small as possible. Moreover, for each pair of nodes and each failure situation, we want to determine the paths on which the demand between the nodes is routed.}, language = {en} } @misc{BorndoerferGroetschelKlostermeieretal., author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and Klostermeier, Fridolin and K{\"u}ttner, Christian}, title = {Telebus Berlin - Mobilit{\"a}t f{\"u}r Behinderte}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-2500}, number = {SC-96-40}, abstract = {Steigendes Mobilit{\"a}tsbed{\"u}rfnis der Behinderten bei angespannter Haushaltslage --- diese Situation ergab vor drei Jahren beim Berliner Behindertenfahrdienst {\em Telebus\/} Handlungsbedarf. Gleichzeitig stie\ss{} die verwendete manuelle (Fahrzeug-)Tourenplanung mit damals etwa 1.000 Fahrtw{\"u}nschen pro Tag an ihre Grenzen. Zur L{\"o}sung dieser Probleme war der effiziente Einsatz von Computern und von {\em mathematischen Optimierungsverfahren\/} erforderlich. Ergebnis des daraufhin gestarteten {\em Telebus-Projektes\/} ist die Entwicklung eines neuen, alle Arbeitsabl{\"a}ufe unterst{\"u}tzenden Computersystems, das seit {\"u}ber einem Jahr im Einsatz ist. Herzst{\"u}ck dieses Systems ist ein auf mathematischen Methoden der ganzzahligen Optimierung basierendes Verfahren zur Tourenplanung. Ziel dieses Artikels ist die Beschreibung dieses Verfahrens und seiner Verwendung bei der Behindertenbef{\"o}rderung. Das Beispiel Telebus zeigt, da\ss{} der Einsatz mathematischer Optimierungstechniken neue M{\"o}glichkeiten f{\"u}r Kosteneinsparungen bei gleichzeitiger Serviceverbesserung auch in anderen Bereichen des {\"O}PNV er{\"o}ffnet.}, language = {de} } @misc{AscheuerGroetschelKaminetal., author = {Ascheuer, Norbert and Gr{\"o}tschel, Martin and Kamin, Nicola and Rambau, J{\"o}rg}, title = {Combinatorial Online Optimization in Practice}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-3508}, number = {SC-98-07}, abstract = {This paper gives a short introduction into combinatorial online optimization. It explains a few evaluation concepts of online algorithms, such as competitiveness, and discusses limitations in their application to real--world problems. The main focus, however, is a survey of combinatorial online problems coming up in practice, in particular, in large scale material flow and flexible manufacturing systems.}, language = {en} } @misc{Groetschel, author = {Gr{\"o}tschel, Martin}, title = {My Favorite Theorem: Characterizations of Perfect Graphs}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4053}, number = {SC-99-17}, abstract = {This paper summarizes and discusses various characterizations of perfect graphs and mentions some open problems in this area.}, language = {en} }