Basic HTML version of Foils prepared August 7 98

Foil 9 Jacobi Iteration: Agglomeration

From DoD HPF Training -- 5. Parallel Programming in HPF DoD Training and Others -- 1995-98. by Chuck Koelbel -- Rice University
1 Element updates require nearest neighbors
  • CYCLIC Þ communicate entire array
  • BLOCK Þ least communication volume
  • (BLOCK,*) Þ move u(i-1,j), u(i+1,j) " j
  • (BLOCK,BLOCK) Þ move u(ILOW-1,j), u(IHIGH+1,j) " j, u(i,JLOW-1), u(i,JHIGH+1) " i
2 Convergence test requires a whole-array reduction
  • Any distribution Þ static, structured communication
3 The bottom line
  • (BLOCK,*) on high-latency machines or small problem sizes
  • (BLOCK,BLOCK) on low-latency machines
in Table To:

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