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Do MPI collective operations involve multiple hops?

  1. May 7, 2013 #1
    Consider the reduce operation for example. Do all nodes send data directly to the root? Or is there some structure where a node will recieve data from a few other nodes, perform a reduction, then pass the intermediate results to other nodes?
     
  2. jcsd
  3. May 7, 2013 #2
    Sth like that could be achieved in two steps using appropriate grouping and using MPI_ALLREDUCE (instead of MPI_REDUCE) first

    Pls attend:
    http://www.mpi-forum.org/docs/mpi22-report/node109.htm#Node109 [Broken]
    and
    Collective Communication - 86. Introduction and Overview
     
    Last edited by a moderator: May 6, 2017
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