Institution
University of Stuttgart
Education•Stuttgart, Germany•
About: University of Stuttgart is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Laser & Finite element method. The organization has 27715 authors who have published 56370 publications receiving 1363382 citations. The organization is also known as: Universität Stuttgart.
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Papers
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01 Feb 2005TL;DR: The work on improving the performance of collective communication operations in MPICH is described, with results indicating that to achieve the best performance for a collective communication operation, one needs to use a number of different algorithms and select the right algorithm for a particular message size and number of processes.
Abstract: We describe our work on improving the performance of collective communication operations in MPICH for clusters connected by switched networks. For each collective operation, we use multiple algorithms depending on the message size, with the goal of minimizing latency for short messages and minimizing bandwidth use for long messages. Although we have implemented new algorithms for all MPI Message Passing Interface collective operations, because of limited space we describe only the algorithms for allgather, broadcast, all-to-all, reduce-scatter, reduce, and allreduce. Performance results on a Myrinet-connected Linux cluster and an IBM SP indicate that, in all cases, the new algorithms significantly outperform the old algorithms used in MPICH on the Myrinet cluster, and, in many cases, they outperform the algorithms used in IBM's MPI on the SP. We also explore in further detail the optimization of two of the most commonly used collective operations, allreduce and reduce, particularly for long messages and nonpower-of-two numbers of processes. The optimized algorithms for these operations perform several times better than the native algorithms on a Myrinet cluster, IBM SP, and Cray T3E. Our results indicate that to achieve the best performance for a collective communication operation, one needs to use a number of different algorithms and select the right algorithm for a particular message size and number of processes.
838 citations
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TL;DR: In this paper, the physics of the nitrogen vacancy and other defect centers from the perspective of single defect center spectroscopy were discussed, where the electron spin wave function hyperfine coupling to close nuclei leads to a splitting in the spectrum which allows for optically detected electron nuclear double resonance.
Abstract: The nitrogen vacancy and some nickel related defects in diamond can be observed as single quantum systems in diamond by their fluorescence. The fabrication of single colour centres occurs via generation of vacancies or via controlled nitrogen implantation in the case of the nitrogen vacancy (NV) centre. The NV centre shows an electron paramagnetic ground and optically excited state. As a result electron and nuclear magnetic resonance can be carried out on single defects. Due to the localized nature of the electron spin wavefunction hyperfine coupling to nuclei more than one lattice constant away from the defect as dominated by dipolar interaction. As a consequence the coupling to close nuclei leads to a splitting in the spectrum which allows for optically detected electron nuclear double resonance. The contribution discusses the physics of the NV and other defect centre from the perspective of single defect centre spectroscopy.
837 citations
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TL;DR: In this article, a review of the fundamentals of zeolite materials science and their application as catalysts is presented, and the most important parameters which allow the preparation of an almost infinite variety of zeolitic materials tailored for a given catalytic application.
835 citations
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TL;DR: In this paper, a polarization potential is incorporated into semi-empirical and Hartree-Fock adjusted pseudopotentials, and very accurate results are obtained for the dimer and hydride ions of alkali elements up to K.
833 citations
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TL;DR: In this paper, an efficient method for the calculation of Breit-Pauli spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions is presented, instead of taking all two-electron contributions of the wavefunction explicitly into account, the most important two-Electron contributions are incorporated by means of an effective oneelectron Fock operator.
Abstract: An efficient method for the calculation of Breit-Pauli spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions is presented. Instead of taking all two-electron contributions of the wavefunction explicitly into account, the most important two-electron contributions of the spin-orbit operator are incorporated by means of an effective one-electron Fock operator. As a further refinement, explicit two-electron contributions can be reinstated for the dominant all-internal parts of the wavefunctions.
826 citations
Authors
Showing all 28043 results
Name | H-index | Papers | Citations |
---|---|---|---|
Yi Chen | 217 | 4342 | 293080 |
Robert J. Lefkowitz | 214 | 860 | 147995 |
Michael Kramer | 167 | 1713 | 127224 |
Andrew G. Clark | 140 | 823 | 123333 |
Stephen D. Walter | 112 | 513 | 57012 |
Fedor Jelezko | 103 | 413 | 42616 |
Ulrich Gösele | 102 | 603 | 46223 |
Dirk Helbing | 101 | 642 | 56810 |
Ioan Pop | 101 | 1370 | 47540 |
Niyazi Serdar Sariciftci | 99 | 591 | 54055 |
Matthias Komm | 99 | 832 | 43275 |
Hans-Joachim Werner | 98 | 317 | 48508 |
Richard R. Ernst | 96 | 352 | 53100 |
Xiaoming Sun | 96 | 382 | 47153 |
Feng Chen | 95 | 2138 | 53881 |