Chapter

Recent Advances in Parallel Virtual Machine and Message Passing Interface

Volume 5759 of the series Lecture Notes in Computer Science pp 325-326

Hierarchical Collectives in MPICH2

  • Hao ZhuAffiliated withLancaster UniversityDepartment of Computer Science, University of Illinois
  • , David GoodellAffiliated withLancaster UniversityMathematics and Computer Science Division, Argonne National Laboratory
  • , William GroppAffiliated withLancaster UniversityDepartment of Computer Science, University of Illinois
  • , Rajeev ThakurAffiliated withLancaster UniversityMathematics and Computer Science Division, Argonne National Laboratory

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Abstract

Most parallel systems on which MPI is used are now hierarchical, such as systems with SMP nodes. Many papers have shown algorithms that exploit shared memory to optimize collective operations to good effect. But how much of the performance benefit comes from tailoring the algorithm to the hierarchical topology of the system? We describe an implementation of many of the MPI collectives based entirely on message-passing primitives that exploits the two-level hierarchy. Our results show that exploiting shared memory directly usually gives small additional benefit and suggests design approaches for where the benefit is large.

Keywords

MPI Collective Communication