Choices, Choices, Choices

• You really need to measure the costs of each to make the best decision

• Rules of thumb:

  • If the data is stored in consecutive entries of an array use the count and datatype parameters to the communication function
  • If you are sending heterogeneous data only once or very few times use MPI_Pack() and MPI_Unpack()
  • Otherwise pick the appropriate derived datatype constructor
    • Homogeneous and regular intervals - MPI_Type_vector
    • Homogeneous and irregular intervals - MPI_Type_indexed
    • Heterogeneous - MPI_Type_struct

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