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Overview |
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StorCloud Challenge Application
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High Accuracy Quantum Theory Computations with the Massively Parallel Quantum Chemistry (MPQC) Program
Curtis Janssen MPQC is a quantum chemistry code developed at Sandia. It can be used to compute molecular energies, geometries, and other properties. It is designed to do as little I/O as possible, keeping most of the intermediates required in main memory or re-computing relatively inexpensive quantities as needed. However, we recently implemented second order Moeller-Plesset perturbation theory explicitly including the inter-electron coordinate (MP2-R12) in MPQC and this method has larger storage requirements than standard Moeller-Plesset perturbation theory (MP2). In MP2-R12, as in MP2, a large four index array of transformed two electron integrals is generated and used to compute the molecular energy. When the distributed integral array is too large to be stored in the aggregate memory of a parallel machine, it can be computed in batches at moderate extra cost. In the MP2 approach each batch has a contribution to the energy independent of all other batches, thus each batch is discarded after the energy contribution is computed. However, in MP2-R12 the energy contains coupled contributions from all of the batches. Thus each batch must be computed, stored and read on each node to form the energy. The availability of high performance parallel storage will make possible computations that cannot currently be done, allowing larger systems to be treated or higher accuracy results to be obtained. The proposed configuration for this application is:
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