Collective Operations (Time - usec) - as function of no.of CPUs

Allgather

Alltoall

Communications among groups of processors in the cluster e.g.

• Distribute data to all nodes in the cluster (scatter, all-to-all)

• Collect data from all nodes (gather)

• Collect information from all nodes to determine an overall condition e.g. minima or maxima (reduce).

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