@misc{Stueben, author = {St{\"u}ben, Hinnerk}, title = {Hadron masses from dynamical, non-perturbatively O(a) improved Wilson fermions}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6205}, number = {00-52}, abstract = {We present results on light hadron masses from simulations of full QCD and report on experiences in running such simulations on a Hitachi SR8000-F1 supercomputer.}, language = {en} } @misc{IlgenfritzKerlerMuellerPreusskeretal., author = {Ilgenfritz, Ernst-Michael and Kerler, Werner and M{\"u}ller-Preussker, Michael and St{\"u}ben, Hinnerk}, title = {Parallel tempering in full QCD with Wilson fermions}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6593}, number = {01-33}, abstract = {We study the performance of QCD simulations with dynamical Wilson fermions by combining the Hybrid Monte Carlo algorithm with parallel tempering on \$10^4\$ and \$12^4\$ lattices. In order to compare tempered with standard simulations, covariance matrices between sub-ensembles have to be formulated and evaluated using the general properties of autocorrelations of the parallel tempering algorithm. We find that rendering the hopping parameter \$\kappa\$ dynamical does not lead to an essential improvement. We point out possible reasons for this observation and discuss more suitable ways of applying parallel tempering to QCD.}, language = {en} } @misc{BaumannBuschGottschewskietal., author = {Baumann, Wolfgang and Busch, Hubert and Gottschewski, J{\"u}rgen and Steinke, Thomas and St{\"u}ben, Hinnerk}, title = {Berliner Landesh{\"o}chstleistungsrechner Parallelrechner Cray T3D/T3E: Betrieb, Nutzung, Projekte, Perspektiven f{\"u}r den Ausbau}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5504}, number = {TR-97-08}, abstract = {Seit fast drei Jahren betreibt das Konrad-Zuse-Zentrum f{\"u}r Informationstechnik Berlin (ZIB) Parallelrechner der h{\"o}chsten Leistungsklasse im normalen Rechenzentrumsbetrieb. Bereits im Mai 1995 hat das ZIB {\"u}ber seine Erfahrungen mit dem damals leistungsst{\"a}rksten Parallelrechner Deutschlands berichtet. Das Gesamtkonzept des ZIB sieht weiterhin einen H{\"o}chstleistungsrechner als unabdingbaren Bestandteil des High Performance Scientific Computing (HPSC) im ZIB vor. Der vorliegende Bericht beschreibt die aktuelle Konfiguration, Betriebserfahrungen und die Rechnernutzung sowie typische Rechenleistungen, die f{\"u}r einzelne Anwendungsprogramme erzielt wurden. Beschreibungen der Forschungsgebiete mit den Forschungsgruppen, die den Rechner nutzen und die Anforderungen an den Rechnerausbau, die sich aus deren Arbeiten herleiten, beschließen den Bericht.}, language = {de} } @misc{IlgenfritzKerlerMuellerPreusskeretal., author = {Ilgenfritz, Ernst-Michael and Kerler, Werner and M{\"u}ller-Preussker, Michael and St{\"u}ben, Hinnerk}, title = {Parallel tempering and decorrelation of topological charge in full QCD}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5930}, number = {00-25}, abstract = {The improvement of simulations of QCD with dynamical Wilson fermions by combining the Hybrid Monte Carlo algorithm with parallel tempering is studied on \$10^4\$ and \$12^4\$ lattices. As an indicator for decorrelation the topological charge is used.}, language = {en} } @misc{KhanBakeyevGoeckeleretal., author = {Khan, Arifa Ali and Bakeyev, Timur and G{\"o}ckeler, Meinulf and Horsley, Roger and Pleiter, Dirk and Rakow, Paul and Sch{\"a}fer, Andreas and Schierholz, Gerrit and St{\"u}ben, Hinnerk}, title = {Accelerating Hasenbusch's Acceleration of Hybrid Monte Carlo}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7520}, number = {03-30}, abstract = {Hasenbusch has proposed splitting the pseudo-fermionic action into two parts, in order to speed-up Hybrid Monte Carlo simulations of QCD. We have tested a different splitting, also using clover-improved Wilson fermions. An additional speed-up between 5 and 20\\% over the original proposal was achieved in production runs.}, language = {en} } @misc{FleurenStuebenZegwaard, author = {Fleuren, Maria and St{\"u}ben, Hinnerk and Zegwaard, Gideon}, title = {MoDySim - A parallel dynamical UMTS simulator}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7489}, number = {03-26}, abstract = {UMTS is a 3rd generation mobile telecommunication system which enables multi-service and multi-bit rate communication going beyond the possibilities of previous systems. The simulator MoDySim models UMTS in great detail. Characteristics of UMTS such as soft hand-over and the interdependency of load and capacity among neighbouring cells are challenges for the parallelisation of such a system. In this paper we explain how the software was parallelised and present performance results of a UMTS simulation for the city of Berlin.}, language = {en} } @misc{IlgenfritzKerlerMuellerPreusskeretal., author = {Ilgenfritz, Ernst-Michael and Kerler, Werner and M{\"u}ller-Preussker, Michael and Sternbeck, Andr{\´e} and St{\"u}ben, Hinnerk}, title = {A numerical reinvestigation of the Aoki phase with \$N_f=2\$ Wilson fermions at zero temperature}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-7492}, number = {03-27}, abstract = {We report on a numerical reinvestigation of the Aoki phase in lattice QCD with two flavors of Wilson fermions where the parity-flavor symmetry is spontaneously broken. For this purpose the Hybrid Monte Carlo algorithm was used and an explicit symmetry-breaking source term \$h\bar{\psi} i \gamma_{5} \tau^{3}\psi\$ was added to the Wilson fermion action. The order parameter \$\langle\bar{\psi}i\gamma_{5}\tau^{3}\psi\rangle\$ was studied at several values of \$(\beta,\kappa,h)\$ on lattices of sizes \$4^4\$ to \$12^4\$. Our largest lattices can be considered as infintely large allowing to extrapolate to \$h=0\$. The existence of a parity-flavor-breaking phase can be confirmed at \$\beta=4.0\$ and \$\beta=4.3\$ while we find no sign of parity-flavor-breaking at \$\beta=4.6\$ and \$\beta=5.0\$.}, language = {en} } @misc{StreuerStueben, author = {Streuer, Thomas and St{\"u}ben, Hinnerk}, title = {Simulations of QCD in the Era of Sustained Tflop/s Computing}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10623}, number = {07-48}, abstract = {The latest machine generation installed at supercomputer centres in Germany offers a peak performance in the tens of Tflop/s range. We study performance and scaling of our quantum chromodynamics simulation programme BQCD that we obtained on two of these machines, an IBM Blue Gene/L and an SGI Altix 4700. We compare the performance of Fortran/MPI code with assembler code. The latter allows to exploit concurrency at more levels, in particular in overlapping communication and computation as well as prefetching data from main memory.}, language = {en} } @misc{IlgenfritzKerlerMuellerPreusskeretal., author = {Ilgenfritz, Ernst-Michael and Kerler, Werner and M{\"u}ller-Preussker, Michael and Sternbeck, Andre and St{\"u}ben, Hinnerk}, title = {Probing the Aoki phase with N_f=2 Wilson fermions at finite temperature}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8812}, number = {05-48}, abstract = {In this letter we report on a numerical investigation of the Aoki phase in the case of finite temperature which continues our former study at zero temperature. We have performed simulations with Wilson fermions at \$\beta=4.6\$ using lattices with temporal extension \$N_{\tau}=4\$. In contrast to the zero temperature case, the existence of an Aoki phase can be confirmed for a small range in \$\kappa\$ at \$\beta=4.6\$, however, shifted slightly to lower \$\kappa\$. Despite fine-tuning \$\kappa\$ we could not separate the thermal transition line from the Aoki phase.}, language = {en} } @misc{HegeStueben, author = {Hege, Hans-Christian and St{\"u}ben, Hinnerk}, title = {Vectorization and Parallelization of Irregular Problems via Graph coloring.}, doi = {/10.1145/109025.109042}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-443}, number = {SC-90-16}, abstract = {Efficient implementations of irregular problems on vector and parallel architectures are generally hard to realize. An important class of problems are Gauß-Seidel iteration schemes applied to irregular data sets. The unstructured data dependences arising there prevent restructuring compilers from generating efficient code for vector or parallel machines. It is shown, how to structure the data dependences by decomposing the underlying data set using graph coloring techniques and by specifying a particular execution order already on the algorithm level. Methods to master the irregularities originating from different types of tasks are proposed. An application is given and some open issues and future developments are discussed.}, language = {en} }