Benefits of topology aware mapping for mesh interconnects

Abhinav Bhatelé, Laxmikant V. Kalé

Research output: Contribution to journalArticlepeer-review

Abstract

The fastest supercomputers today such as Blue Gene/L, Blue Gene/P, Cray XT3 and XT4 are connected by a three-dimensional torus/mesh interconnect. Applications running on these machines can benefit from topology-awareness while mapping tasks to processors at runtime. By co-locating communicating tasks on nearby processors, the distance traveled by messages and hence the communication traffic can be minimized, thereby reducing communication latency and contention on the network. This paper describes preliminary work utilizing this technique and performance improvements resulting from it in the context of a n-dimensional k-point stencil program. It shows that even for simple benchmarks, topology-aware mapping can have a significant impact on performance. Automated topology-aware mapping by the runtime using similar ideas can relieve the application writer from this burden and result in better performance. Preliminary work towards achieving this for a molecular dynamics application, NAMD, is also presented. Results on up to 32,768 processors of IBMs Blue Gene/L, 4,096 processors of IBMs Blue Gene/P and 2,048 processors of Crays XT3 support the ideas discussed in the paper.

Original languageEnglish (US)
Pages (from-to)549-566
Number of pages18
JournalParallel Processing Letters
Volume18
Issue number4
DOIs
StatePublished - Dec 2008

Keywords

  • Mapping
  • Mesh
  • Performance
  • Scaling
  • Supercomputers
  • Topology
  • Torus

ASJC Scopus subject areas

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture

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