Nathan Wichmann

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The Gemini interconnect on the Cray XE6 platform provides for lightweight remote direct memory access (RDMA) between nodes, which is useful for implementing partitioned global address space languages like UPC and Co-Array Fortran. In this paper, we perform a study of Gemini performance using a set of communication microbenchmarks and compare the performance(More)
We present novel parallel language constructs for the communication intensive part of a magnetic fusion simulation code. The focus of this work is the shift phase of charged particles of a tokamak simulation code in toroidal geometry. We introduce new hybrid PGAS/OpenMP implementations of highly optimized hybrid MPI/OpenMP based communication kernels. The(More)
In this paper we explore new parallel language constructs for the communication kernel of a real world magnetic fusion simulation code using the Partitioned Global Address Space (PGAS) model. The studied kernel is the particle shift phase of a tokamak simulation code in a toroidal geometry, which models the transit of charged particles between neighboring(More)
NERSC has partnered with 20 representative application teams to evaluate performance on the Xeon-Phi Knights Landing architecture and develop an application-optimization strategy for the greater NERSC workload on the recently installed Cori system. In this article, we present early case studies and summarized results from a subset of the 20 applications(More)
We develop a method for improving the parallel scalability of the recently developed parallel selected inversion algorithm [Jacquelin, Lin and Yang 2014], named PSelInv, on massively parallel distributed memory machines. In the PSelInv method, we compute selected elements of the inverse of a sparse matrix A that can be decomposed as A = LU , where L is(More)
MSC.Nastran V70.7 was used on the Cray SV1 to perform large-scale NVH problems typically encountered in the automotive industry. Several MSC.Nastran solution sequences such as SOL 103, 111, 108, and 107 are heavily used by automotive customers in a production environment on the Cray SV1. Significant performance improvements were recently made to key(More)
CHIMERA is a multi-dimensional radiation hydrodynamics code designed to study core-collapse supernovae. The code is made up of three essentially independent parts: hydrodynamics, nuclear burning, and a neutrino transport solver combined within an operator-split approach. The multi-physics nature of the problem, and the specific implementation of that(More)