@misc{ReinefeldStuebenSchintkeetal.2002, author = {Reinefeld, Alexander and St{\"u}ben, Hinnerk and Schintke, Florian and Din, George}, title = {GuiGen: A Toolset for Creating Customized Interfaces for Grid User Communities}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-6737}, number = {02-06}, year = {2002}, abstract = {\textsf{\itshape{GuiGen}} is a comprehensive set of tools for creating customized graphical user interfaces (GUIs). It draws from the concept of computing portals, which are here seen as interfaces to application-specific computing services for user communities. While \textsf{\itshape{GuiGen}} was originally designed for the use in computational grids, it can be used in client/server environments as well. Compared to other GUI generators, \textsf{\itshape{GuiGen}} is more versatile and more portable. It can be employed in many different application domains and on different target platforms. With \textsf{\itshape{GuiGen}}, application experts (rather than computer scientists) are able to create their own individually tailored GUIs.}, language = {en} } @misc{BuschDroebesFroehlichetal.2007, author = {Busch, Hubert and Droebes, Ursula and Fr{\"o}hlich, Marek and Schimmel, Christian}, title = {Das Berliner Wissenschaftsnetz BRAIN 2007}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10458}, number = {07-42}, year = {2007}, abstract = {Berlin als Stadtstaat ist Kommune und Land der Bundesrepublik zugleich und Standort vieler renommier-ter Wissenschafts- und Kultureinrichtungen. In enger Zusammenarbeit der Wissenschaftseinrichtungen mit dem IT-Dienstleistungszentrum Berlin (ITDZ, ehemals Landesbetrieb f{\"u}r Informationstechnik), der f{\"u}r die Beh{\"o}rden Berlins zust{\"a}ndigen Einrichtung, wurde seit 1993 ein landeseigenes Glasfasernetz mit einer derzeitigen L{\"a}nge von 856 km Glasfaserkabel (je Kabel bis zu 144 Einzelfasern) zur gemeinsamen Nutzung von Wissenschaft und Verwaltung errichtet und weiter ausgebaut. 1994 erfolgte der offizielle Start des Berliner Wissenschaftsnetzes BRAIN (Berlin Research Area Information Network), als durch einen Beschluss des Senats von Berlin die Nutzung des landeseigenen Glasfasernetzes durch die Wissen-schaftseinrichtungen festgeschrieben wurde. Bereits 1995 wurden durch die Wissenschaftseinrichtungen auf diesem Glasfasernetz die ersten sieben Anschl{\"u}sse in ATM-Technik (Classical BRAIN-ATM) in Betrieb genommen, 1999 wurden anschließend auch erste Strecken in Ethernet-Technik (Classical BRAIN-GE) betrieben. Diese heterogenen Netze mit unterschiedlichen Netzger{\"a}ten wurden dezentral von den Netzadministratoren der beteiligten Einrichtungen nach globalen Absprachen betreut. Die dezentrale Administration erschwerte das Management und die Erweiterungen der Gesamtnetze. Basierend auf den vorliegenden Erfahrungen vereinbarten die Berliner Wissenschaftseinrichtungen, ein technisch neues Verbundnetz in Gigabit-Ethernet-Technik mit einheitlichen Ger{\"a}ten und einem zentralen Netzwerkmana-gement aufzubauen und zu betreiben. Seit November 2003 betreibt BRAIN auf dem landeseignen Glasfasernetz ein auf MPLS-Technik basie-rendes Gigabit-Ethernet-Netz, das „BRAIN-Verbundnetz", mit den Diensten LAN-to-LAN-Kopplung der Einrichtungen, regionaler IP-Verkehr, {\"U}bergang zum Verwaltungsnetz und WiN-Backup. Das BRAIN-Verbundnetz l{\"o}ste die dezentral betreuten Vorl{\"a}ufernetze komplett ab. Von den derzeit 27 BRAIN-Teilnehmern nutzen 24 Einrichtungen an 53 in der Stadt verteilten Standorten die Dienste des BRAIN-Verbundnetzes, 18 Standorte sind mit 1000 Mbit/s und 35 Standorte mit 100 Mbit/s angeschlossen. F{\"u}r verteilte Standorte einer Einrichtung besteht zudem die M{\"o}glichkeit, diese {\"u}ber dedizierte Fasern oder Bandbreiten miteinander zu vernetzen. Seit dem 2. Quartal 2007 wird im Rahmen eines Pilotprojekts der Nutzen eines zentral gemanagten Fibre Channel-Netzwerks "BRAIN-SAN" ermittelt, um M{\"o}glichkeiten einer verteilten Datenhaltung der Berliner Hochschulen und wissenschaftlichen Einrichtungen zu schaf-fen. Zus{\"a}tzlich zu den vorgenannten Diensten nutzt der DFN-Verein die BRAIN-Struktur f{\"u}r die Verbindun-gen der X-WiN-Kernnetzknoten in Berlin und Potsdam untereinander und f{\"u}r Zugangsleitungen zu den Anwendern. Mit Stand 2007 nutzt das Berliner Wissenschaftsnetz BRAIN vom landeigenen Glasfasernetz 2100 km Einzelfasern und verbindet insgesamt 43 Einrichtungen (BRAIN-Teilnehmer und DFN-Anwender) aus Wissenschaft, Bildung und Kultur mit 129 Standorten. Der Betrieb von BRAIN wird im wesentlichen durch seine Nutzer finanziert. Das Land Berlin tr{\"a}gt aller-dings pauschal die {\"u}berwiegenden Kosten f{\"u}r die Wartung des Glasfasernetzes, soweit es vom ITDZ be-reit gestellt wird. Zentrales Planungs- und Steuerungsorgan f{\"u}r BRAIN ist die von der Senatsverwaltung f{\"u}r Bildung, Wis-senschaft und Forschung eingerichtete BRAIN-Planungsgruppe. Sie besteht aus Mitarbeitern der Rechen-zentren der drei Berliner Universit{\"a}ten und des ZIB. Nach außen wird BRAIN in rechtlicher und wirtschaftlicher Hinsicht treuh{\"a}nderisch vom ZIB vertreten, die BRAIN-Gesch{\"a}ftsstelle befindet sich ebenfalls im ZIB.}, language = {de} } @misc{Plantikow2007, author = {Plantikow, Stefan}, title = {Transaktionen f{\"u}r verteilte Wikis auf strukturierten Overlay-Netzwerken}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10466}, number = {07-43}, year = {2007}, abstract = {Die Arbeit pr{\"a}sentiert ein Transaktionsverfahren f{\"u}r strukturierte Overlay-Netzwerke, das an die Erfordernisse verteilter Informationssysteme mit relationalem Datenmodell angepasst ist. Insbesondere wird der Einsatz von Transaktionen f{\"u}r verteilte Wikis betrachtet, die moderne Funktionalit{\"a}ten, wie Metadaten und zus{\"a}tzliche Indexe f{\"u}r die Navigation, unterst{\"u}tzen. Konsistenz und Dauerhaftigkeit der gespeicherten Daten erfordert die Behandlung von Knotenausf{\"a}llen. Die Arbeit schl{\"a}gt daf{\"u}r das Zellenmodell vor: Das Overlay wird aus replizierten Zustandsmaschinen gebildet, um Verf{\"u}gbarkeit zu gew{\"a}hrleisten. Das Transaktionsverfahren baut darauf auf und verwendet Two-Phase-Commit mit Fehlererkennung und Widerherstellung von ausgefallenen Transaktionsmanagern. Anwendungen wird eine Auswahl an pessimistischen und hybrid-optimistischen Nebenl{\"a}ufigkeitskontrollverfahren geboten, die die Minimierung von Latenzeffekten und die schnelle Ausf{\"u}hrung von Nur-Lese-Transaktionen erm{\"o}glichen. F{\"u}r die Beispielanwendung Wiki wird der erforderliche Pseudocode angegeben und die verschiedenen Nebenl{\"a}ufigkeitskontrollverfahren hinsichtlich ihrer Nachrichtenkomplexit{\"a}t verglichen.}, language = {de} } @misc{Lichtenstein2006, type = {Master Thesis}, author = {Lichtenstein, Tom}, title = {Implementation eines Resourcebrokers im Kontext eines Grid-Datenmanagement-Systems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9968}, school = {Zuse Institute Berlin (ZIB)}, year = {2006}, language = {de} } @misc{Meltzer2006, type = {Master Thesis}, author = {Meltzer, J{\"o}rg}, title = {Vergleich von Co-Reservierungs-Algorithmen in Grid-Umgebungen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9972}, school = {Zuse Institute Berlin (ZIB)}, year = {2006}, abstract = {In dieser Arbeit werden effiziente Co-Reservierungs-Algorithmen vorgestellt, mit denen Rechenressourcen mehrerer Cluster im Grid reserviert werden k{\"o}nnen. Es werden f{\"u}nf Algorithmen vorgestellt, die flexible Co-Reservierungsanfragen erm{\"o}glichen. In einer Co-Reservierungsanfrage m{\"u}ssen die angeforderten CPUs der Teilreservierungen exakt festgelegt werden. Die Cluster und die Startzeiten, bei denen die Teilreservierungen durchgef{\"u}hrt werden, ermittelt ein Co-Reservierungs-Algorithmus erst bei der Anfragebearbeitung. Die Benutzer k{\"o}nnen die Startzeit in der Anfrage eingrenzen, in dem sie eine fr{\"u}heste Startzeit und eine Deadline angeben. In den bisher entwickelten Reservierungsverfahren k{\"o}nnen Benutzer nur starre Co-Reservierungsanfragen stellen, in denen sie f{\"u}r alle Attribute der Teilreservierungen exakte Werte angeben m{\"u}ssen. Eine flexible Co-Reservierungsanfrage erlaubt einem Grid-Reservierungsdienst optimierte Reservierungsvarianten durchzuf{\"u}hren, da er aus vielen Reservierungsvarianten ausw{\"a}hlen kann. Die Anwendungen von lokalen Benutzern k{\"o}nnen durch die Grid-Reservierungen verz{\"o}gert werden. Bei der Auswahl der Reservierungsvarianten kann ein Grid-Reservierungsdienst dies ber{\"u}cksichtigen und den negativen Einfluß der Grid-Reservierungen verringern. Bei zwei Co-Reservierungs-Algorithmen werden auch zus{\"a}tzliche Sortiervorgaben des Klienten bei der Auswahl der Reservierungsvarianten beachtet. Die Algorithmen wurden durch Simulationen mit dem Workload eines realen großen Supercomputers ausgewertet. Die Untersuchungen zeigen, daß sowohl die lokalen als auch die Grid-Benutzer von den flexiblen Anfragen profitieren k{\"o}nnen. Den lokalen Benutzern wurden die Ressourcen weniger oft durch zu fr{\"u}h gestellte Reservierungsanfragen entzogen. Die Grid- Benutzer k{\"o}nnen ihrerseits komfortabel eine optimierte Reservierungsvariante durchf{\"u}hren lassen.}, language = {de} } @misc{Moser2006, type = {Master Thesis}, author = {Moser, Monika}, title = {Platzierung von Replikaten in Verteilten Systemen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9995}, school = {Zuse Institute Berlin (ZIB)}, year = {2006}, language = {de} } @misc{ReinefeldSchintkeSchuett2007, author = {Reinefeld, Alexander and Schintke, Florian and Sch{\"u}tt, Thorsten}, title = {P2P Routing of Range Queries in Skewed Multidimensional Data Sets}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9671}, number = {07-23}, year = {2007}, abstract = {We present a middleware to store multidimensional data sets on Internet-scale distributed systems and to efficiently perform range queries on them. Our structured overlay network \emph{SONAR (Structured Overlay Network with Arbitrary Range queries)} puts keys which are adjacent in the key space on logically adjacent nodes in the overlay and is thereby able to process multidimensional range queries with a single logarithmic data lookup and local forwarding. The specified ranges may have arbitrary shapes like rectangles, circles, spheres or polygons. Empirical results demonstrate the routing performance of SONAR on several data sets, ranging from real-world data to artificially constructed worst case distributions. We study the quality of SONAR's routing information which is based on local knowledge only and measure the indegree of the overlay nodes to find potential hot spots in the routing process. We show that SONAR's routing table is self-adjusting, even under extreme situations, keeping always a maximum of \$\lceil \log N \rceil\$ routing entries.}, language = {en} } @misc{Pham2005, type = {Master Thesis}, author = {Pham, The Anh}, title = {Einbettung neuer Verwaltungsmethoden in die hierarchische Dateisystemsicht}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10014}, school = {Zuse Institute Berlin (ZIB)}, year = {2005}, abstract = {Die hierarchische Organisation von Dateien beherrscht Computersysteme seit vielen Jahren und wird sich vermutlich auch in Zukunft weiterhin durchsetzen. Dennoch st{\"o}ßt diese Verwaltungsmethode in einem klassischen hierarchischen Dateisystem bei dem j{\"a}hrlichen rasanten Zuwachs an neuen Daten an ihre Grenzen, auch wenn Nutzer eine ausgefeilte Verzeichnisstruktur mit einer disziplinierten Namensgebung konsequent auf- und ausbauen. Um den {\"U}berblick {\"u}ber die Dateien zu behalten, werden in dieser Arbeit neue Verwaltungsmethoden vorgestellt und in die hierarchische Dateisystemsicht eingebettet. Auf der Basis des hierarchischen Dateisystems bietet ein metadatenbasiertes Dateisystem neben dem hierarchischen Zugriff noch einen flexiblen, assoziativen Zugriff auf Dateien {\"u}ber virtuelle Objekte, indem Suchmethoden in Form einer Anfrage auf in einer Datenbank gespeicherte Index- und Metadaten angewendet werden. Das Ergebnis dieser Abfrage wird mit Hilfe von virtuellen Verzeichnissen und virtuellen Dateien in einer {\"u}bersichtlichen Form dargestellt, so dass eine Nutzung der hierarchischen Sicht weiterhin intuitiv fortgesetzt wird. Das Datenmanagementsystem ZIBDMS, welches einen verteilten Metadatenkatalog und einen Dateireplikationskatalog beinhaltet, erm{\"o}glicht es, die oben genannten Verwaltungsmethoden f{\"u}r die NFS-Schnittstelle, CORBA-Middleware und Web Services transparent zu implementieren. Zudem stellt ZIBDMS weitere neue Dateiverwaltungsmethoden zur Verf{\"u}gung, die sich in die hierarchische Dateisystemsicht integrieren lassen. Metadaten in Form von Attribut-Wert-Paaren lassen sich als virtuelle Datei darstellen und editieren. Eine Collection bietet die M{\"o}glichkeit, Dateien in einem logischen virtuellen Ordner zu organisieren. Mit einem Dependency-Graph lassen sich Dateien zueinander in Relation stellen, so dass eine Linkstruktur zwischen Dateien ausgedr{\"u}ckt werden kann. Das Verweiskonzept eines klassischen hierarchischen Dateisystems wird im ZIBDMS um eine neue Verweisart Weak-Link erweitert, um einen aktualisierbaren, konsistenten und zyklenfreien symbolischen Link anzubieten. In einer hierarchischen Sicht l{\"a}sst sich durch Verweise ein Baum bilden, in dem eine Navigation und Verweisauflistung m{\"o}glich sind, was außer ZIBDMS noch kein anderes System bietet.}, language = {de} } @misc{Rieche2003, type = {Master Thesis}, author = {Rieche, Simon}, title = {Lastbalancierung in Peer-to-Peer Systemen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10048}, school = {Zuse Institute Berlin (ZIB)}, year = {2003}, abstract = {Peer-to-Peer (P2P) Systeme werden u.a. zur Verwaltung von großen Datenmengen benutzt, die auf verschiedene Rechner verteilt sind. Benutzern soll damit der Zugriff auf Daten innerhalb des Systems leicht erm{\"o}glicht werden. Damit in P2P Systemen die Daten effizient verteilt und gesucht werden k{\"o}nnen, existieren Distributed Hash Tables. Distributed Hash Tables (DHT) sind eine Methode, um globale Informationen persistent speichern zu k{\"o}nnen. Der Wertebereich der Hashfunktion, welche die zu ver{\"o}ffentlichenden Eintr{\"a}ge auf Werte abbildet, wird in Abschnitte aufgeteilt, die einzelnen Knoten zugeteilt werden. Die meisten DHTs haben aber ein Problem bei der Verteilung der Last. Die verschiedenen DHT Systeme beruhen meist auf einem identischen Ansatz der Lastverteilung. Die Last wird nur mit Hilfe einer Hashfunktion verteilt. Es wird davon ausgegangen, dass diese Funktion die Last gleichm{\"a}ßig verteilt. Im Rahmen dieser Arbeit wurde ein Verfahren zur Last Verteilung entwickelt, simuliert und implementiert. Bei dem Verfahren wird die Last wie bei der Verteilung von W{\"a}rme an die Umgebung abgegeben. Es wird mit existierenden Lastbalancierungsalgorithmen verglichen. Mit diesem neuen Verfahren ist es m{\"o}glich, Last in DHTs besser zu verteilen ohne große {\"A}nderungen an den DHTs vorzunehmen. Es wird gezeigt, wie mit dem Verfahren zus{\"a}tzlich die Fehlertoleranz des P2P Systems erh{\"o}ht werden kann.}, language = {de} } @misc{Schintke2000, type = {Master Thesis}, author = {Schintke, Florian}, title = {Ermittlung von Programmlaufzeiten anhand von Speicherzugriffen, Microbenchmarks und Simulation von Speicherhierarchien}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10063}, school = {Zuse Institute Berlin (ZIB)}, year = {2000}, abstract = {Kostenmodelle dienen der Ermittlung von Programmlaufzeiten, zum Vergleich der Effizienz von Algorithmen und zur Analyse des Verhaltens von Speicherhierarchien. Ein neuartiges Kostenmodell ist das Latency-of-Data-Access (LDA) Modell, das mehrere hierarchische Speicherebenen mit unterschiedlichen Latenzzeiten ber{\"u}cksichtigt. In dieser Diplomarbeit wird ein Simulator f{\"u}r Speicherhierarchien pr{\"a}sentiert, der die Berechnung von Programmausf{\"u}hrungszeiten nach dem LDA-Modell erlaubt. Mit Hilfe des Simulators wird die These gepr{\"u}ft, daß mit diesem Modell die Ausf{\"u}hrungszeit eines Programms ad{\"a}quat abgesch{\"a}tzt werden kann. Mit dem Simulator ist es erstmals praktikabel m{\"o}glich, Programmausf{\"u}hrungszeiten nach dem LDA-Modell zu bestimmen. Der Simulator kann f{\"u}r Systeme mit unterschiedlichen Speicherarchitekturen konfiguriert werden und unterst{\"u}tzt Mehrprozessorsysteme mit gemeinsamem Speicher (SMP-Systeme) mit verschiedenen Koh{\"a}renzprotokollen. Der Simulator kann mit den Ergebnissen von Microbenchmarks konfiguriert werden, die die Architekturparameter einer Speicherhierarchie messen. Die Ergebnisse best{\"a}tigen die These nicht nur f{\"u}r Einzelprozessorsysteme, sondern auch f{\"u}r SMP-Systeme, wo gleichzeitig interagierende Prozessoren gegenseitig ihre Zugriffsse-quenz auf Zwischenspeicher beeinflussen. Zus{\"a}tzlich wurde eine neue Einsatzm{\"o}glichkeit des LDA-Modells entwickelt, um die Ausf{\"u}hrungszeit von Programmteilen zu bestimmen. Einzelne Zugriffskosten k{\"o}nnen einem mehrerer parallel laufender Modelle zugeordnet werden. Dadurch k{\"o}nnen Kosten, die Zugriffe auf einzelne Speicherbereiche verursachen, separat bestimmt werden. Diese Profiling-Technik erlaubt Optimierungen an Datenstrukturen und Speicherzugriffsmustern durch pr{\"a}zise und gezielte Informationsproduktion.}, language = {de} } @misc{Schuett2002, type = {Master Thesis}, author = {Sch{\"u}tt, Thorsten}, title = {Synchronisation von verteilten Verzeichnisstrukturen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10071}, school = {Zuse Institute Berlin (ZIB)}, year = {2002}, abstract = {Das Management von großen Datenmengen spielt eine immer wichtigere Rolle, wie aktuelle Entwicklungen in der Hochenergiephysik [2] zeigen. F{\"u}r das DataGrid-Projekt zum Beispiel ist es notwendig, große Datenmengen auf mehrere Rechenzentren in Europa zu verteilen und die Daten untereinander zu synchronisieren. Auch innerhalb von Clustern gewinnen mit zunehmender Anzahl der Knoten Werkzeuge zur effizienten Synchronisation und Verteilung von Daten an Bedeutung. Im Rahmen dieser Arbeit wurde ein effizientes Verfahren zur Synchronisation von verteilten Verzeichnisstrukturen entwickelt und implementiert. Mit diesem Verfahren ist es m{\"o}glich, unabh{\"a}ngige {\"A}nderungen an beliebigen Repositories gleichzeitig durchzuf{\"u}hren. Das Verfahren ben{\"o}tigt keine zentrale Instanz, wodurch eine gegen{\"u}ber vielen existierenden Verfahren verbesserte Skalierbarkeit erreicht werden konnte. Dabei wurden Erkenntnisse aus der Graphentheorie eingesetzt und weiterentwickelt, um die Netzwerktopolo-gie und -handbreiten zwischen den Rechnern zu ber{\"u}cksichtigen. Durch die Verwendung einer Offline-Synchronisation werden {\"A}nderungen erst dann an andere Rechner propagiert, wenn der Nutzer dies anst{\"o}ßt. Das kann zum Beispiel nach einer abgeschlossenen Transaktion, die {\"A}nderungen an mehreren Dateien beinhaltet, angemessen sein.}, language = {de} } @misc{Witte2005, type = {Master Thesis}, author = {Witte, Jochen}, title = {Implementierung einer NFS Schnittstelle im Kontext eines Grid-Datenmanagement-Systems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10081}, school = {Zuse Institute Berlin (ZIB)}, year = {2005}, abstract = {Diese Arbeit dokumentiert den Entwurf und die Implementierung einer NFS-Schnittstelle zum ZIBDMS. Das ZIBDMS, welches derzeit am Zuse-Institut Berlin entwickelt wird, ist ein Managementsystem f{\"u}r verteilte Daten in heterogenen Umgebungen [10]. Es soll die einfache Benutzung von Mechanismen zur Replikation sowie neue M{\"o}glichkeiten des Zugriffs und der Verwaltung von Metadaten und Datenobjekten erm{\"o}glichen. Dem Nutzer bietet das System verschiedene Sichten: Neben der klassischen, hierarchischen Sicht mit Verzeichnissen und Dateien wird auch eine attributbasierte Zugriffsmethode angeboten, in der Datenobjekte ausschließlich {\"u}ber Attribut/Wert-Paare referenziert werden. F{\"u}r den Benutzer transparent, soll sich das System im Hinblick auf die Verf{\"u}gbarkeit von Daten und Metadaten selbstt{\"a}tig optimieren. Um Skalierbarkeit gew¨ahrleisten zu k{\"o}nnen, werden intern Peer-to-Peer- Techniken entwickelt und benutzt. Die NFS-Schnittstelle erh{\"o}ht die Nutzbarkeit des Systems, da Client- Implementierungen f{\"u}r nahezu alle Betriebssysteme zur Verf{\"u}gung stehen. Der Benutzer kann so {\"u}ber das gewohnte Dateisystem Daten und Metadaten pflegen, ohne spezifisches Vorwissen zu ben{\"o}tigen. In dieser Arbeit wird untersucht, inwiefern sich die Semantik des ZIBDMS auf jene des NFS-Protokolls {\"u}bertragen l{\"a}ßt. Weiterhin wird das Konzept von Pseudodateien beschrieben und diskutiert, inwiefern es eine brauchbare L{\"o}sung darstellt, den im Vergleich zur NFS-Semantik wesentlich gr{\"o}ßeren Funktionsumfang des ZIBDMS f{\"u}r den Anwender nutzbar zu machen. Pseudodateien sind nicht-persistente Objekte, welche f{\"u}r den Benutzer als regul{\"a}re Datei sichtbar werden und die erweiterte Funktionalit{\"a}ten wie die Bearbeitung von Metadaten oder die Platzierung von Replikaten {\"u}ber die Dateisystem-Sicht des NFS zur Verf{\"u}gung stellen sollen. Schließlich werden Leistungsmessungen an den benutzten Komponenten des ZIBDMS vorgenommen und vergleichbaren Systemen gegen {\"u}bergestellt. Die Aufmerksamkeit liegt hier auf der zugrundeliegenden Katalog-Technologie sowie dem durch das NFS-Protokoll verursachten Overhead.}, language = {de} } @misc{SchuettSchintkeReinefeld2005, author = {Sch{\"u}tt, Thorsten and Schintke, Florian and Reinefeld, Alexander}, title = {Chord\#: Structured Overlay Network for Non-Uniform Load-Distribution}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-8736}, number = {05-40}, year = {2005}, abstract = {\newcommand{\chordsharp}{Chord\$^\\#\#\$} Data lookup is a fundamental problem in peer-to-peer systems: Given a key, find the node that stores the associated object. Chord and other P2P algorithms use distributed hash tables (DHTs) to distribute the keys and nodes evenly across a logical ring. Using an efficient routing strategy, DHTs provide a routing performance of \$O (\log N)\$ in networks of \$N\$ nodes. While the routing performance has been shown to be optimal, the uniform key distribution makes it impossible for DHTs to support range queries. For range queries, consecutive keys must be stored on lo gically neighboring nodes. In this paper, we present an enhancement of Chord that eliminates the hash function while keeping the same routing performance. The resulting algorithm, named \chordsharp{}, provides a richer function ality while maintaining the same complexity. In addition to Chord, \chordsharp{} adapts to load imbalance.}, language = {en} } @article{SalemSchintke2021, author = {Salem, Farouk and Schintke, Florian}, title = {Load balancing mechanism for FLESnet}, journal = {CBM Progress Report 2020}, doi = {10.15120/GSI-2021-00421}, pages = {156 -- 157}, year = {2021}, language = {en} } @misc{MokhtariPattersonHoefling2021, author = {Mokhtari, Zahra and Patterson, Robert I. A. and H{\"o}fling, Felix}, title = {Spontaneous trail formation in populations of auto-chemotactic walkers}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-84466}, year = {2021}, abstract = {We study the formation of trails in populations of self-propelled agents that make oriented deposits of pheromones and also sense such deposits to which they then respond with gradual changes of their direction of motion. Based on extensive off-lattice computer simulations aiming at the scale of insects, e.g., ants, we identify a number of emerging stationary patterns and obtain qualitatively the non-equilibrium \add{state} diagram of the model, spanned by the strength of the agent--pheromone interaction and the number density of the population. In particular, we demonstrate the spontaneous formation of persistent, macroscopic trails, and highlight some behaviour that is consistent with a dynamic phase transition. This includes a characterisation of the mass of system-spanning trails as a potential order parameter. We also propose a dynamic model for a few macroscopic observables, including the sub-population size of trail-following agents, which captures the early phase of trail formation.}, language = {en} } @misc{LemkeSteinHoelteretal.2021, author = {Lemke, Mathias and Stein, Lewin and H{\"o}lter, Arne and Weinzierl, Stefan}, title = {Adjungierten-basierte Synthese und Bestimmung optimaler Treiberfunktionen von Lautsprechern mit komplexer Richtcharakteristik}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, isbn = {978-3-939296-18-8}, doi = {https://doi.org/10.14279/depositonce-12515}, year = {2021}, abstract = {Die Bestimmung optimaler Treiberfunktionen von Lautsprechern mit frequenzabh{\"a}ngiger Richtcharakteristik ist ein schlecht gestelltes Optimierungsproblem. Zu dessen L{\"o}sung haben die Autoren in vorangegangenen Beitr{\"a}gen eine adjungierten-basierte Methode zur Optimierung von Lautsprecher-Arrays im Zeitbereich vorgestellt [5, 6, 8]. Diese erm{\"o}glicht unter anderem die Ber{\"u}cksichtigung von Berandungen und Umgebungseffekten wie Wind, war jedoch bisher auf monopol-artige Quellen beschr{\"a}nkt. Um diese Einschr{\"a}nkung zu beheben, haben die Autoren einen adjungierten-basierten Zeitbereichsansatz mit Finiten-Differenzen (FDTD) zur Synthese komplexer synthetischer Schallquellen durch diskrete, gitter-basierte Monopole vorgestellt [4, 9]. In diesem Beitrag demonstrieren die Autoren die entsprechende Modellierung eines realen Zweiwege-Monitors (A). Zudem wird gezeigt, wie sich die Vielzahl der zur Synthese verwendeten Monopole in eine Lautsprecher-Treiberfunktion {\"u}berf{\"u}hren lassen (B).}, language = {de} } @article{LeserHilbrichDraxletal.2021, author = {Leser, Ulf and Hilbrich, Marcus and Draxl, Claudia and Eisert, Peter and Grunske, Lars and Hostert, Patrick and Kainm{\"u}ller, Dagmar and Kao, Odej and Kehr, Birte and Kehrer, Timo and Koch, Christoph and Markl, Volker and Meyerhenke, Henning and Rabl, Tilmann and Reinefeld, Alexander and Reinert, Knut and Ritter, Kerstin and Scheuermann, Bj{\"o}rn and Schintke, Florian and Schweikardt, Nicole and Weidlich, Matthias}, title = {The Collaborative Research Center FONDA}, volume = {21}, journal = {Datenbank-Spektrum}, number = {3}, doi = {10.1007/s13222-021-00397-5}, pages = {255 -- 260}, year = {2021}, language = {en} } @article{PathaniaChakrabortyHoefling2021, author = {Pathania, Yogyata and Chakraborty, Dipanjan and H{\"o}fling, Felix}, title = {Continuous demixing transition of binary liquids: finite-size scaling from the analysis of sub-systems}, volume = {4}, journal = {Advances Theory and Simulation}, doi = {10.1002/adts.202000235}, pages = {2000235}, year = {2021}, language = {en} } @article{FroembergHoefling2021, author = {Fr{\"o}mberg, Daniela and H{\"o}fling, Felix}, title = {Generalized master equation for first-passage problems in partitioned spaces}, volume = {54}, journal = {Journal of Physics A: Mathematical and Theoretical}, doi = {10.1088/1751-8121/abf2ec}, pages = {215601}, year = {2021}, language = {en} } @article{KleinEbrahimiViandHoeflingetal.2021, author = {Klein, Rupert and Ebrahimi Viand, Roya and H{\"o}fling, Felix and Delle Site, Luigi}, title = {Nonequilibrium induced by reservoirs: Physico-mathematical model and numerical tests}, volume = {4}, journal = {Advances Theory and Simulation}, doi = {10.1002/adts.202100071}, pages = {2100071}, year = {2021}, language = {en} } @article{GholamiHoeflingKleinetal.2021, author = {Gholami, Abbas and H{\"o}fling, Felix and Klein, Rupert and Delle Site, Luigi}, title = {Thermodynamic relations at the coupling boundary in adaptive resolution simulations for open systems}, volume = {4}, journal = {Advances Theory and Simulation}, doi = {10.1002/adts.202000303}, pages = {2000303}, year = {2021}, language = {en} } @article{MokhtariPattersonHoefling2022, author = {Mokhtari, Zahra and Patterson, Robert I. A. and H{\"o}fling, Felix}, title = {Spontaneous trail formation in populations of auto-chemotactic walkers}, volume = {24}, journal = {New Journal of Physics}, doi = {10.1088/1367-2630/ac43ec}, pages = {013012}, year = {2022}, language = {en} } @inproceedings{ClauseckerKaiser2021, author = {Clausecker, Robert and Kaiser, Benjamin}, title = {Sliding Tile Puzzles}, booktitle = {Proceedings of SAT Competition 2021 : Solver and Benchmark Descriptions}, pages = {57}, year = {2021}, language = {en} } @article{RodriguesPelaHsiaoHultmanetal.2024, author = {Rodrigues Pela, Ronaldo and Hsiao, Ching-Lien and Hultman, Lars and Birch, Jens and Gueorguiev, Gueorgui Kostov}, title = {Electronic and optical properties of core-shell InAlN nanorods: a comparative study via LDA, LDA-1/2, mBJ, HSE06, G0W0 and BSE methods}, volume = {26}, journal = {Physical Chemistry Chemical Physics}, publisher = {Royal Society of Chemistry}, arxiv = {http://arxiv.org/abs/https://arxiv.org/abs/2309.14889}, doi = {10.1039/D3CP05295H}, pages = {7504 -- 7514}, year = {2024}, language = {en} } @article{JuhaszSerraLakatosetal.2023, author = {Juhasz, Anett and Serra, Uneri Haymana and Lakatos, Csilla and Vadkerti, Bence and Ragyanszki, Anita and Farkas, Odon and Keki, Sandor and Nagy, Lajos}, title = {The kinetics of uncatalyzed and catalyzed urethane forming reactions of aliphatic diisocyanates with butan-1-ol}, volume = {47}, journal = {New J. Chem.}, doi = {10.1039/d3nj02747c}, pages = {16096 -- 16107}, year = {2023}, abstract = {The kinetics of the urethane forming reactions of hexamethylene diisocyanate (HDI), 4,4′-dicyclohexyl-methane-diisocyanate (HMDI) and isophorone diisocyanate (IPDI) with butan-1-ol were systematically studied by electrospray ionization mass spectrometry (ESI-MS) in the off-line mode. The reactions were performed in toluene solution in the temperature range of 50-80 °C and perdeuterated butan-1-ol was used for quenching the reaction. The butan-1-ol was employed in high excess to diisocyanates to obtain pseudo first-order rate coefficients. For rendering the kinetics, a simple A → B → C consecutive model was applied and found to adequately describe the observed kinetic behaviors. The corresponding rate coefficients were determined and reactivities of the diisocyanates were found to decrease in the order HDI > IPDI > HMDI. Furthermore, it was observed that the second isocyanate group in HDI, due to the ring formation by intramolecular hydrogen bonds, reacted faster with butan-1-ol after the first isocyanate moiety had reacted. The formation of hydrogen bonding rings was also confirmed by DFT calculations. However, the reactivity of the second isocyanate moiety (after the first one has reacted) did not change significantly in the case of HMDI. From the temperature dependences the apparent activation parameters such as the pre-exponential factors and activation energies were determined. In addition, the reactions were also studied at 80 °C in the presence of tin(II)-2-ethylhexanoate at different concentrations and a mechanism was proposed for the catalytic process.}, language = {en} } @article{JiRagyanszkiFournier2023, author = {Ji, Hongchen and Ragyanszki, Anita and Fournier, Rene A.}, title = {Machine learning estimation of reaction energy barriers}, volume = {1229}, journal = {Computational and Theoretical Chemistry}, doi = {10.1016/j.comptc.2023.114332}, pages = {114332}, year = {2023}, abstract = {We describe a machine learning approach to approximate reaction energy barriers (E), requiring as input only estimates of geometry and energies of reactants and products. Using the dataset of Grambow, Pattanaik, and Green [Sci. Data 7 (1 3 7) (2020)] for reactions involving seven or fewer non-hydrogen atoms, 300 reaction features are computed, and an estimate of E is obtained by fitting a Kernel Ridge Regression (KRR) model with Laplacian kernel to a subset of Density Functional Theory reaction barriers. Our main interest is small energy barriers with the goal of modeling reactions in the interstellar medium and circumstellar envelope. We omitted reactions with E > 40 kcal mol-1 to obtain a subset of 5,276 reactions for 5-fold cross-validation. For this set, the KRR model predicts E with a mean absolute error of 4.13 kcal mol-1 and a root-mean square error of 6.02 kcal mol-1.}, language = {en} } @inproceedings{ChristgauEveringhamMikolajczaketal.2023, author = {Christgau, Steffen and Everingham, Dylan and Mikolajczak, Florian and Schelten, Niklas and Schnor, Bettina and Schroetter, Max and Stabernack, Benno and Steinert, Fritjof}, title = {Enabling Communication with FPGA-based Network-attached Accelerators for HPC Workloads}, booktitle = {Proceedings of the SC'23 Workshops of The International Conference on High Performance Computing, Network, Storage, and Analysis, SC-W 2023, Denver, CO, USA, November 12-17, 2023}, publisher = {ACM}, doi = {10.1145/3624062.3624540}, pages = {530 -- 538}, year = {2023}, abstract = {The use of stand-alone, network-coupled Field Programmable Gate Array (FPGA) accelerators is intended to significantly increase the energy efficiency of HPC applications and thus also of HPC data centers. A loose coupling between the nodes of the HPC data center and the FPGAs is established through the high-speed network of the data center. This allows greater flexibility in combining different nodes and accelerators. Both the resulting energy savings and the increased flexibility through the network connection, enable the economical use of FPGAs. This work presents a communication stack to integrate the so-called Network-attached Accelerator (NAA) into the HPC data center. A low-level Remote Direct Memory Access (RDMA) Application Programming Interface (API) and a high-level Remote Procedure Call (RPC) API is designed on top of the RDMA over Converged Ethernet v2 (RoCEv2) communication stack. The experimental results over 100 Gbps RoCEv2 show that our design and implementation deliver performance close to the theoretical maximum.}, language = {en} } @article{HoeflingDietrich2024, author = {H{\"o}fling, Felix and Dietrich, Siegfried}, title = {Structure of liquid-vapor interfaces: perspectives from liquid state theory, large-scale simulations, and potential grazing-incidence X-ray diffraction}, volume = {160}, journal = {The Journal of Chemical Physics}, arxiv = {http://arxiv.org/abs/2311.06425}, doi = {10.1063/5.0186955}, pages = {104107}, year = {2024}, abstract = {Grazing-incidence X-ray diffraction (GIXRD) is a scattering technique which allows one to characterize the structure of fluid interfaces down to the molecular scale, including the measurement of the surface tension and of the interface roughness. However, the corresponding standard data analysis at non-zero wave numbers has been criticized as to be inconclusive because the scattering intensity is polluted by the unavoidable scattering from the bulk. Here we overcome this ambiguity by proposing a physically consistent model of the bulk contribution which is based on a minimal set of assumptions of experimental relevance. To this end, we derive an explicit integral expression for the background scattering, which can be determined numerically from the static structure factors of the coexisting bulk phases as independent input. Concerning the interpretation of GIXRD data inferred from computer simulations, we account also for the finite sizes of the bulk phases, which are unavoidable in simulations. The corresponding leading-order correction beyond the dominant contribution to the scattered intensity is revealed by asymptotic analysis, which is characterized by the competition between the linear system size and the X-ray penetration depth in the case of simulations. Specifically, we have calculated the expected GIXRD intensity for scattering at the planar liquid--vapor interface of Lennard-Jones fluids with truncated pair interactions via extensive, high-precision simulations. The reported data cover interfacial and bulk properties of fluid states along the whole liquid--vapor coexistence line. A sensitivity analysis demonstrates the robustness of our findings concerning the detailed definition of the mean interface position. We conclude that previous claims of an enhanced surface tension at mesoscopic scales are amenable to unambiguous tests via scattering experiments.}, language = {en} } @inproceedings{KaiserClauseckerMavroskoufis2023, author = {Kaiser, Benjamin and Clausecker, Robert and Mavroskoufis, Michael}, title = {Prioritised Unit Propagation by Partitioning the Watch Lists}, volume = {3545}, booktitle = {Proceedings of the 14th International Workshop on Pragmatics of SAT co-located with the 26th International Conference on Theory and Applications of Satisfiability Testing (SAT 2023)}, publisher = {CEUR Workshop Proceedings}, pages = {14 -- 34}, year = {2023}, abstract = {Conflict Driven Clause Learning (CDCL) SAT solvers spend most of their execution time iterating through clauses in unit propagation. Efficient implementations of unit propagation mostly rely on the two watched literals (TWL) scheme, a specialised data structure watching two literals per clause to prevent as many clause lookups as possible. In this paper, we present Priority Propagation (PriPro)—a minimally invasive method to adapt unit propagation in existing SAT solvers. With PriPro the traditional TWL scheme is partitioned to allow for rearranging the order in which clauses are examined. This is used to achieve a prioritisation of certain clauses. Using PriPro in combination with a dynamic heuristic to prioritise resolvents from recent conflicts, the effectiveness of unit propagation can be increased. In the state-of-the-art CDCL SAT solver CaDiCaL modified to use PriPro, we obtained a 5-10 \% speedup on the SAT Competition 2021 benchmark set in a fair comparison with the unmodified CaDiCaL.}, language = {en} } @article{PolichtMittenzweyDogadovetal.2023, author = {Policht, Veronica R. and Mittenzwey, Henry and Dogadov, Oleg and Katzer, Manuel and Villa, Andrea and Li, Qiuyang and Kaiser, Benjamin and Ross, Aaron M. and Scotognella, Francesco and Zhu, Xiaoyang and Knorr, Andreas and Selig, Malte and Cerullo, Giulio and Dal Conte, Stefano}, title = {Time-domain observation of interlayer exciton formation and thermalization in a MoSe2/WSe2 heterostructure}, volume = {14}, journal = {Nature Communications}, publisher = {Springer Nature}, doi = {10.1038/s41467-023-42915-x}, pages = {1 -- 9}, year = {2023}, abstract = {Vertical heterostructures of transition metal dichalcogenides (TMDs) host interlayer excitons with electrons and holes residing in different layers. With respect to their intralayer counterparts, interlayer excitons feature longer lifetimes and diffusion lengths, paving the way for room temperature excitonic optoelectronic devices. The interlayer exciton formation process and its underlying physical mechanisms are largely unexplored. Here we use ultrafast transient absorption spectroscopy with a broadband white-light probe to simultaneously resolve interlayer charge transfer and interlayer exciton formation dynamics in a MoSe2/WSe2 heterostructure. We observe an interlayer exciton formation timescale nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute this relative delay to an interplay of a phonon-assisted interlayer exciton cascade and thermalization, and excitonic wave-function overlap. Our results may explain the efficient photocurrent generation observed in optoelectronic devices based on TMD heterostructures, as the interlayer excitons are able to dissociate during thermalization.}, language = {en} } @inproceedings{SkoblinHoeflingChristgau2023, author = {Skoblin, Viktor and H{\"o}fling, Felix and Christgau, Steffen}, title = {Gaining Cross-Platform Parallelism for HAL's Molecular Dynamics Package using SYCL}, volume = {36}, booktitle = {29. PARS-Workshop 2023}, issn = {0177-0454}, arxiv = {http://arxiv.org/abs/2406.04210}, year = {2023}, abstract = {Molecular dynamics simulations are one of the methods in scientific computing that benefit from GPU acceleration. For those devices, SYCL is a promising API for writing portable codes. In this paper, we present the case study of HAL's MD package that has been successfully migrated from CUDA to SYCL. We describe the different strategies that we followed in the process of porting the code. Following these strategies, we achieved code portability across major GPU vendors. Depending on the actual kernels, both significant performance improvements and regressions are observed. As a side effect of the migration process, we obtained impressing speedups also for execution on CPUs.}, language = {en} } @article{ClauseckerLemire2023, author = {Clausecker, Robert and Lemire, Daniel}, title = {Transcoding unicode characters with AVX-512 instructions}, volume = {53}, journal = {Software: Practice and Experience}, number = {12}, publisher = {John Wiley \& Sons Ltd.}, doi = {10.1002/spe.3261}, pages = {2430 -- 2462}, year = {2023}, abstract = {Intel includes in its recent processors a powerful set of instructions capable of processing 512-bit registers with a single instruction (AVX-512). Some of these instructions have no equivalent in earlier instruction sets. We leverage these instructions to efficiently transcode strings between the most common formats: UTF-8 and UTF-16. With our novel algorithms, we are often twice as fast as the previous best solutions. For example, we transcode Chinese text from UTF-8 to UTF-16 at more than 5 GiB s-1 using fewer than 2 CPU instructions per character. To ensure reproducibility, we make our software freely available as an open-source library. Our library is part of the popular Node.js JavaScript runtime.}, language = {en} } @article{GholamiSchintke2023, author = {Gholami, Masoud and Schintke, Florian}, title = {CAWL: A Cache-aware Write Performance Model of Linux Systems}, journal = {arXiv}, arxiv = {http://arxiv.org/abs/2306.05701}, doi = {10.48550/arXiv.2306.05701}, pages = {1 -- 22}, year = {2023}, language = {en} } @article{SchintkeDeMecquenemGuarinoetal.2023, author = {Schintke, Florian and De Mecquenem, Ninon and Guarino, Vanessa Emanuela and Hilbrich, Marcus and Lehmann, Fabian and Sattler, Rebecca and Sparka, Jan Arne and Speckhard, Daniel and Stolte, Hermann and Vu, Anh Duc and Leser, Ulf}, title = {Validity Constraints for Data Analysis Workflows}, journal = {arXiv}, arxiv = {http://arxiv.org/abs/2305.08409}, doi = {10.48550/arXiv.2305.08409}, pages = {1 -- 28}, year = {2023}, language = {en} } @article{RodriguesPelaVonaLubecketal.2024, author = {Rodrigues Pela, Ronaldo and Vona, Cecilia and Lubeck, Sven and Alex, Ben and Gonzalez Oliva, Ignacio and Draxl, Claudia}, title = {Critical assessment of G0W0 calculations for 2D materials: the example of monolayer MoS2}, volume = {10}, journal = {npj Comput. Mater.}, arxiv = {http://arxiv.org/abs/https://arxiv.org/abs/2310.04198}, doi = {10.1038/s41524-024-01253-2}, pages = {77}, year = {2024}, language = {en} } @article{CharronMusilGuljasetal.2025, author = {Charron, Nicholas and Musil, F{\´e}lix and Guljas, Andrea and Chen, Yaoyi and Bonneau, Klara and Pasos-Trejo, Aldo and Jacopo, Venturin and Daria, Gusew and Zaporozhets, Iryna and Kr{\"a}mer, Andreas and Templeton, Clark and Atharva, Kelkar and Durumeric, Aleksander and Olsson, Simon and P{\´e}rez, Adri{\`a} and Majewski, Maciej and Husic, Brooke and Patel, Ankit and De Fabritiis, Gianni and No{\´e}, Frank and Clementi, Cecilia}, title = {Navigating protein landscapes with a machine-learned transferable coarse-grained model}, volume = {17}, journal = {Nature Chemistry}, arxiv = {http://arxiv.org/abs/2310.18278}, doi = {10.1038/s41557-025-01874-0}, pages = {1284 -- 1292}, year = {2025}, abstract = {The most popular and universally predictive protein simulation models employ all-atom molecular dynamics (MD), but they come at extreme computational cost. The development of a universal, computationally efficient coarse-grained (CG) model with similar prediction performance has been a long-standing challenge. By combining recent deep learning methods with a large and diverse training set of all-atom protein simulations, we here develop a bottom-up CG force field with chemical transferability, which can be used for extrapolative molecular dynamics on new sequences not used during model parametrization. We demonstrate that the model successfully predicts folded structures, intermediates, metastable folded and unfolded basins, and the fluctuations of intrinsically disordered proteins while it is several orders of magnitude faster than an all-atom model. This showcases the feasibility of a universal and computationally efficient machine-learned CG model for proteins.}, language = {en} } @article{KrishnadasCharronFournier2025, author = {Krishnadas, Anirudh and Charron, Nicolas and Fournier, Rene}, title = {Melting Transitions in Small Aluminum Clusters Simulated with Energies Approaching DFT Accuracy.}, journal = {ACS Publications- Journal of Chemical Theory and Computation}, year = {2025}, abstract = {We describe a computational framework for modelling melting-like transitions in atomic clusters that combines first-principles energy calculations, global optimization, and machine-learned interatomic potentials. A diverse set of configurations is generated by global optimization, and energies are calculated by Density Functional Theory. The energies are fitted to an accuracy of 10 meV/atom or better with an Allegro E(3)-equivariant neural network potential. The model allows efficient parallel tempering Monte Carlo simulations with near DFT-level accuracy. This methodology was validated by simulating Na_20 and comparing it to earlier experimental and computational results. We used it to study melting-like transitions in Al_n+ clusters (n=9 to 16), and Al_n and Al_n^- (n=12, 13,14). The simulated heat capacity of these clusters, in particular Al_16+, are in qualitative agreement with experiments. The melting point of Al_n+ clusters with n=11-16 are well above the bulk melting point (934 K). The closed-shell Al_13- species has an exceptionally high melting point, close to 2100 K.}, language = {en} } @article{KrishnadasMoshiQuintanaetal.2025, author = {Krishnadas, Anirudh and Moshi, Maryam and Quintana, Ramon Alain Miranda and Fournier, Rene}, title = {Geometric Features and a Neural Network Classifier for Detecting Melting-Like Transitions in Clusters.}, journal = {AIP Publications - The Journal of Chemical Physics}, year = {2025}, abstract = {Melting-like transitions in clusters are normally identified by a peak in the heat capacity curve C(T ) at T = Tc. Computing C(T ) requires costly simulations with millions of steps. We discuss four easily calculated functions of temperature that help detect and characterize melting-like transitions. The first, f1 (or WU ), is the width of the potential energy distribution which shows an abrupt increase near Tc. The other three are statistics of the ordered set of N(N - 1)/2 interatomic distances rij: (i) f2 is a measure of dissimilarity to the lowest energy configuration, or global minimum; (ii) f3 is the effective number of rij's found in a small interval centered around (r1 + r2)/2 where r1, r2 are the positions of the first two peaks in the pair distribution function; and (iii) f4 is a measure of non-uniformity in the distribution of the ri j's. Numerical tests with empirical potentials that model three types of bonding (van der Waals, covalent, and metallic) show that f1, f2, f3, and f4 produce estimates for the middle of the melting region in general agreement with Tc. An Artificial Neural Network (ANN) classifier that takes, as inputs, f2, f3, and many variants of f4, is used to calculate the solid fraction FS(T) and find the solid-liquid coexistence region between freezing and melting temperatures, [Tf , Tm]. Inflection points in f3(T ) and FS(T ) are very sensitive indicators of phase transitions. Estimates of Tc obtained from them converge one to three orders of magnitude faster, in simulation time, than those obtained with C(T ).}, language = {en} } @article{ClauseckerLemireSchintke2025, author = {Clausecker, Robert and Lemire, Daniel and Schintke, Florian}, title = {Faster Positional-Population Counts for AVX2, AVX-512, and ASIMD}, volume = {37}, journal = {Concurrency and Computation: Practice and Experience}, number = {27-28}, publisher = {Wiley}, issn = {1532-0626}, doi = {10.1002/cpe.70435}, year = {2025}, language = {en} } @article{HoelterLemkeWeinzierletal.2025, author = {H{\"o}lter, Arne and Lemke, Mathias and Weinzierl, Stefan and Stein, Lewin}, title = {Non-Reflecting Characteristic Boundary Conditions for Adjoint Time-Domain Acoustic Simulations}, journal = {Journal of Theoretical and Computational Acoustics}, year = {2025}, abstract = {Accurate acoustic simulations in the free field require non-reflective boundary conditions to suppress spurious reflections at the computational domain boundaries. Although several characteristic-based formulations for direct (forward) simulations have been proposed in recent decades, the adjoint formulations of such characteristic-based boundary conditions (CBCs) have received limited atten- tion in the literature and lack a comprehensive analysis. This paper presents the derivation and evaluation of adjoint CBCs complementing the existing direct CBCs. Both the forward and adjoint CBCs are applied to the (nonlinear) Euler equations and linear acoustic equations in time-domain simulations. In this manner, the CBCs are investigated and subsequently compared to assess their respective accuracy and consistency. The CBCs were implemented using both a single-point and a zonal approach, with the former optionally combined with a sponge layer. Both approaches yielded comparable results in direct and adjoint simulations, while the zonal CBC exhibited improved ac- curacy at lower frequencies. Across the evaluated frequency range of approximately 350 - 5600 Hz, spurious reflections were attenuated by up to -70dB in both forward and adjoint cases, demon- strating the effectiveness and consistency of the proposed boundary treatment.}, language = {en} } @article{RaharinirinaSunkaravonKleistetal.2024, author = {Raharinirina, Nomenjanahary Alexia and Sunkara, Vikram and von Kleist, Max and Fackeldey, Konstantin and Weber, Marcus}, title = {Multi-Input data ASsembly for joint Analysis (MIASA): A framework for the joint analysis of disjoint sets of variables}, volume = {19}, journal = {PLOS ONE}, number = {5}, publisher = {Public Library of Science}, doi = {10.1371/journal.pone.0302425}, pages = {26}, year = {2024}, language = {en} } @article{RodriguesPelaDraxl2024, author = {Rodrigues Pel{\´a}, Ronaldo and Draxl, Claudia}, title = {Speeding up all-electron real-time TDDFT demonstrated by the exciting package}, volume = {304}, journal = {Comput. Phys. Commun.}, arxiv = {http://arxiv.org/abs/https://arxiv.org/abs/2403.04351}, doi = {10.1016/j.cpc.2024.109292}, pages = {109292}, year = {2024}, language = {en} } @article{HoeflingStraube2025, author = {H{\"o}fling, Felix and Straube, Arthur}, title = {Langevin equations and a geometric integration scheme for the overdamped limit of rotational Brownian motion of axisymmetric particles}, volume = {7}, journal = {Physical Review Research}, arxiv = {http://arxiv.org/abs/2403.04501}, doi = {10.1103/wzdn-29p4}, pages = {043034}, year = {2025}, abstract = {The translational motion of anisotropic or self-propelled colloidal particles is closely linked with the particle's orientation and its rotational Brownian motion. In the overdamped limit, the stochastic evolution of the orientation vector follows a diffusion process on the unit sphere and is characterized by an orientation-dependent ("multiplicative") noise. As a consequence, the corresponding Langevin equation attains different forms depending on whether Itō's or Stratonovich's stochastic calculus is used. We clarify that both forms are equivalent and derive them in a top-down approach from a geometric construction of Brownian motion on the unit sphere, based on infinitesimal random rotations. Our approach suggests further a geometric integration scheme for rotational Brownian motion, which preserves the normalization constraint of the orientation vector exactly. We show that a simple implementation of the scheme, using Gaussian random rotations, converges weakly at order 1 of the integration time step, and we outline an advanced variant of the scheme that is weakly exact for an arbitrarily large time step. Due to a favorable prefactor of the discretization error, already the Gaussian scheme allows for integration time steps that are one order of magnitude larger compared to a commonly used algorithm for rotational Brownian dynamics simulations based on projection on the constraining manifold. For torques originating from constant external fields, we prove by virtue of the Fokker-Planck equation that the constructed diffusion process satisfies detailed balance and converges to the correct equilibrium distribution. The analysis is restricted to time-homogeneous rotational Brownian motion (i.e., a single rotational diffusion constant), which is relevant for axisymmetric particles and also chemically anisotropic spheres, such as self-propelled Janus particles.}, language = {en} } @misc{SchintkeGrevedeCuveland2024, author = {Schintke, Florian and Greve, Nico and de Cuveland, Jan}, title = {Recent Flesnet developments and work in progress}, journal = {CBM Progress Report 2023}, editor = {Friese, Volker and Gasik, Piotr and Selyuzhenkov, Ilya}, publisher = {GSI Helmholtzzentrum f{\"u}r Schwerionenforschung GmbH}, doi = {10.15120/GSI-2024-00765}, pages = {132}, year = {2024}, language = {en} } @inproceedings{WitzkeLoesserBountrisetal.2024, author = {Witzke, Joel and L{\"o}ßer, Ansgar and Bountris, Vasilis and Schintke, Florian and Scheuermann, Bj{\"o}rn}, title = {I/O of Scientific Workflows Monitored in Detail}, booktitle = {20th IEEE International Conference on e-Science, e-Science 2024, Osaka, Japan, September 16-20, 2024}, doi = {10.1109/E-SCIENCE62913.2024.10678728}, pages = {1 -- 2}, year = {2024}, language = {en} } @article{WitzkeLoesserBountrisetal.2024, author = {Witzke, Joel and L{\"o}ßer, Ansgar and Bountris, Vasilis and Schintke, Florian and Scheuermann, Bj{\"o}rn}, title = {Low-level I/O Monitoring for Scientific Workflows}, volume = {abs/2408.00411}, journal = {CoRR}, arxiv = {http://arxiv.org/abs/2408.00411}, doi = {10.48550/ARXIV.2408.00411}, pages = {1 -- 10}, year = {2024}, language = {en} } @article{FritschSchorr2024, author = {Fritsch, Daniel and Schorr, Susan}, title = {Disorder induced band gap lowering in kesterite type Cu2ZnSnSe4 and Ag2ZnSnSe4: a first-principles and special quasirandom structures investigation}, volume = {36}, journal = {Journal of Physics: Condensed Matter}, number = {37}, publisher = {IOP Publishing}, issn = {0953-8984}, doi = {10.1088/1361-648X/ad52de}, year = {2024}, abstract = {Abstract Quaternary chalcogenides, i.e. Cu2ZnSnS4, crystallising in the kesterite crystal structure have already been demonstrated as potential building blocks of thin film solar cells, containing only abundant elements and exhibiting power conversion efficiencies of about 14.9\% so far. However, due to the potential presence of several structurally similar polymorphs, the unequivocal identification of their ground state crystal structures required the application of more elaborate neutron diffraction experiments. One particular complication arose from the later identified Cu-Zn disorder, present in virtually all thin film samples. Subsequently, it has been shown experimentally that this unavoidable Cu-Zn disorder leads to a band gap lowering in the respective samples. Additional theoretical investigations, mostly based on Monte-Carlo methods, tried to understand the atomistic origin of this disorder induced band gap lowering. Here, we present theoretical results from first-principles calculations based on density functional theory for the disorder induced band gap lowering in kesterite Cu2ZnSnSe4 and Ag2ZnSnSe4, where the Cu-Zn and Ag-Zn disorder is modelled via a supercell approach and special quasirandom structures. Results of subsequent analyses of structural, electronic, and optical properties are discussed with respect to available experimental results, and will provide additional insight and knowledge towards the atomistic origin of the observed disorder induced band gap lowering in kesterite type materials.}, language = {en} } @inproceedings{KramerLaeuter2024, author = {Kramer, Tobias and L{\"a}uter, Matthias}, title = {Benchmarking the rotating jet model of cometary activity with the trajectory of comet 67P/Churyumov-Gerasimenko}, volume = {17}, booktitle = {EPSC Abstracts}, doi = {10.5194/epsc2024-207}, year = {2024}, abstract = {An important tool to assess the composition and the spatial origin of cometary material is the analysis of its trajectory reflecting gravitational acceleration due to solar system bodies complemented by non-gravitational accelerations (NGA).}, language = {en} } @article{AttreeGutierrezGroussinetal.2024, author = {Attree, Nicholas and Guti{\´e}rrez, Pedro and Groussin, Olivier and B{\"u}rger, Johanna and Keller, Horst Uwe and Kramer, Tobias and LASAGNI MANGHI, RICCARDO and L{\"a}uter, Matthias and Lemos, Pablo and Markkanen, Johannes and Marschall, Raphael and Schuckart, Christian}, title = {Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques}, volume = {690}, journal = {Astronomy and Astrophysics}, arxiv = {http://arxiv.org/abs/2408.10877}, doi = {10.1051/0004-6361/202450728}, pages = {A82}, year = {2024}, abstract = {Aims. We investigate the ability of a simultaneous fitting of comet 67P/Churyumov-Gerasimenko's non-gravitational forces, torques, and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models of cometary material. Methods. We extend the previous work of fitting geographically defined surface outgassing models to the Rosetta observations by testing the effects of a more detailed geomorphological mapping, the resolution of the shape-model used, self-heating by neighbouring facets on the shape-model, thermal inertia in the outgassing solution, and the variation in the momentum coupling between the gas and the nucleus. We also directly compare the non-gravitational acceleration curves available in the literature. Results. We correct an error in the calculation of pole-orientation in the previous paper. We find that, under the assumptions of the model, non-gravitational forces and torques are driven by water sublimation from the nucleus, thermal inertia and self-heating have only minor effects, spatially uniform activity cannot explain 67P's non-gravitational dynamics, spatially uniform momentum transfer cannot explain 67P's non-gravitational dynamics, and different terrain types have different instantaneous responses to insolation. Conclusions. Consolidated terrain facing south on 67P/Churyumov-Gerasimenko has a high outgassing flux, a steep response to insolation, and a large gas momentum transfer coefficient. Instead, that facing north behaves differently, producing little to no water outgassing, and with a lower momentum transfer efficiency. Dusty terrain also has a lower outgassing rate and momentum transfer efficiency, and either depletes its volatile component or is buried in fall-back as the comet approaches the Sun. Momentum transfer appears correlated with insolation, likely due to an increased enhancement in the gas temperature as the dust it flows through is heated.}, language = {en} } @inproceedings{AttreeGutierrezGroussinetal.2024, author = {Attree, Nicholas and Guti{\´e}rrez, Pedro and Groussin, Olivier and B{\"u}rger, Johanna and Keller, Horst Uwe and Kramer, Tobias and Lasagni Manghi, Riccardo and L{\"a}uter, Matthias and Lemos, Pablo and Markkanen, Johannes and Marschall, Raphael and Schuckart, Christian}, title = {The Results of ISSI Team \#547: Understanding the Activity of Comets Through 67P's Dynamics}, volume = {17}, booktitle = {EPSC Abstracts}, doi = {10.5194/epsc2024-82}, year = {2024}, abstract = {Understanding cometary activity gives us an insight into the materials properties, and therefore formation and evolution processes of these relatively pristine protoplanetary objects. We will present the results of an International Space Science Institute project to investigate the phenomenon through the effects of the outgassing activity on the orbit and spin-state of comet 67P/Churymov-Gerasimenko, e.g. its non-gravitational dynamics. This International Team gathered experts in orbital dynamics and trajectory reconstruction together with thermophysical modellers and comet observationalists, in order to compare the available extractions of 67P's non-gravitational acceleration (NGA) from its trajectory. The team then fitted a combination of the NGA, the non-gravitational torque (NGT), and the total water-outgassing rate with a thermophysical activity model. The results of this model will be presented. In particular, it was found that: non-gravitational forces and torques are driven by water sublimation from the nucleus; thermal inertia and self-heating have only minor effects; spatially uniform activity cannot explain 67P's non-gravitational dynamics; spatially uniform momentum transfer cannot explain 67P's non-gravitational dynamics; and different terrain types have different instantaneous responses to insolation. The implications of these findings for the modelling of cometary material and the variety of surface types seen on 67P will be discussed.}, language = {en} } @article{RoyHoefling2024, author = {Roy, Sutapa and H{\"o}fling, Felix}, title = {Critical surface adsorption of confined binary liquids with locally conserved mass and composition}, volume = {122}, journal = {Molecular Physics}, number = {21-22}, doi = {10.1080/00268976.2024.2391998}, pages = {e2391998}, year = {2024}, abstract = {Close to a solid surface, the properties of a fluid deviate significantly from their bulk values. In this context, we study the surface adsorption profiles of a symmetric binary liquid confined to a slit pore by means of molecular dynamics simulations; the latter naturally entails that mass and concentration are locally conserved. Near a bulk consolute point, where the liquid exhibits a demixing transition with the local concentration as the order parameter, we determine the order parameter profiles and characterise the relevant critical scaling behaviour, in the regime of strong surface attraction, for a range of pore widths and temperatures. The obtained order parameter profiles decay monotonically near the surfaces, also in the presence of a pronounced layering in the number density. Overall, our results agree qualitatively with recent theoretical predictions from a mesoscopic field-theoretical approach for the canonical ensemble.}, language = {en} } @phdthesis{Jami2024, author = {Jami, Masoud}, title = {Optimizing Checkpoint/Restart and Input/Output for Large Scale Applications}, publisher = {Humboldt-Universit{\"a}t zu Belin}, doi = {10.18452/29985}, pages = {162}, year = {2024}, language = {en} }