Example: Why MPI Datatypes

Example: Why MPI Datatypes

• Handling non-contiguous data
• Assume must pack/unpack on each end
  • cn + (s + rn) + cn
• Can move directly
  • s + r’ n
  • r’ probably > r but < (2c+r)
• MPI implementation must copy data anyway (into network buffer or shared memory); having the datatype permits removing 2 copies

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