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Q/A Exercise 3

ANSWERS:

Q- Take a careful look at the output; is the task's order guaranteed? Try to run the code 3 times.

A- The processes are independent and their termination order is basically not guaranteed.

Q- What function call can you use instead of the pair ISEND/IRECV?

A- A send-receive operation is very useful for executing a shift operation across a chain of processes:

MPI_SENDRECV

int MPI_Sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype, int dest, int sendtag, void *recvbuf, int recvcount, MPI_Datatype recvtype, int source, int recvtag, MPI_Comm comm, MPI_Status *status)

MPI_SENDRECV(SENDBUF, SENDCOUNT, SENDTYPE, DEST, SENDTAG, RECVBUF, RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM, STATUS, IERROR) <type> SENDBUF(*), RECVBUF(*) INTEGER SENDCOUNT, SENDTYPE, DEST, SENDTAG, RECVCOUNT, RECVTYPE, SOURCE, RECV TAG, COMM, STATUS(MPI_STATUS_SIZE), IERROR

Try to modify the code in order to call the SENDRECV function instead of the SEND and RECV calls.