Scatter

• Scatter; the one-to-all scatter operation is performed in MPI using the MPI_Scatter function.

  int MPI_Scatter(void *sendbuf, int sendcount, 
          MPI_Datatype senddatatype, void *recvbuf, int recvcount, 
          MPI_Datatype recvdatatype, int source, MPI_Comm comm)
  

• The source process sends a different part of the send buffer sendbuf to each processes, including itself.
• The data that are received are stored in recvbuf.
• Process i receives sendcount contiguous elements of type senddatatype starting from the i * sendcount location of the sendbuf of the source process (assuming that sendbuf is of the same type as senddatatype).
• Similarly to the gather operation, MPI provides a vector variant of the scatter operation, called MPI_Scatterv, that allows different amounts of data to be sent to different processes.

Figure 5.5: Diagram for Scatter.