An Introduction to Parallel Programming by Tobias Wittwer

By Tobias Wittwer

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Open MPI: Goals, Concept, and Design of a Next Generation MPI Implementation. Proceedings, 11th European PVM/MPI Users’ Group Meeting, Budapest, Hungary. , 2006. High-Performance Implementation of the Level-3 BLAS. ACM Transactions on Mathematical Software, submitted. , 1996. A high-performance, portable implementation of the MPI message passing interface standard. Parallel Computing 22 (6), 789-828. , 1996. User’s Guide for mpich, a Portable Implementation of MPI. Mathematics and Computer Science Division, Argonne National Laboratory, Chicago, IL.

If the observations are sorted by latitude, this can improve the computation time considerably. This technique is used in many Fortran programs, often using Fortran’s SAVE statement, which saves the values of variables between subroutine calls. Be careful, though: subroutines making use of save and being called by parallel threads will result in wrong results. Because of this, SHALE saves ji−1 outside of the subroutine actually using it, with a private copy of the variable for every thread. 1 Description The previous chapter presented the “direct method” for solving linear equation systems, in this case for spherical harmonic analysis.

7 shows the resulting runtimes for the multiplication N = AT A (PDSYRK), the solving of Nx = b (PDPOSV), and the total program runtime. 2. DIRECT METHOD 39 the resulting performance and efficiency of the PDSYRK routine. For 4 and 8 nodes, efficiency is around 60%. Using more than leads to a significant drop in efficency. Using 32 nodes actually slows the program down compared to 16 nodes, as too much time is spent communicating. Only the PDPOSV routine benefits from 32 nodes. Note that especially PDPOSV is sensitive to the selected ScaLAPACK block size.

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