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MPI Barrier

COMP328 Lectures

Barrier (Synchronisation)

We may use syncrnonisation for the following reasons:

  • Debugging:
    • We can test communication speed (not load imbalance) by using a barrier before a gather.
  • Ensure various task have been completed before continuing:
    • We could also test for completion in a loop while running other non-dependant tasks.
  • Reducing side-effects for time sensitive code.
  • Enforce ordering.

Barrier Syntax

C Syntax
       #include <mpi.h>
       int MPI_Barrier(MPI_Comm comm)

We should be careful when using barrier as it can significantly slow down code.