Rookie HPC

Datatypes

C

MPI_INT32_T

Definition

MPI_INT32_T is an MPI_Datatype that represents a 4-byte integer type in MPI, it corresponds to an int32_t in C. For the FORTRAN counterpart, please see MPI_INTEGER4.

Example

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#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <mpi.h>

/**
 * @brief Illustrate how to communicate a 4-byte int between 2 MPI processes.
 * @details This application is meant to be run with 2 MPI processes: 1 sender
 * and 1 receiver. The former sends a 4-byte int to the latter, which prints it.
 **/
int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    // Check that 2 MPI processes are used.
    int size;
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    if(size != 2)
    {
        printf("This application is meant to be run with 2 MPI processes.\n");
        MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
    }

    // Get my rank and do the corresponding job.
    enum role_ranks { SENDER, RECEIVER };
    int my_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
    switch(my_rank)
    {
        case SENDER:
        {
            // Send the int
            int32_t intToSend = 123456789;
            printf("[MPI process %d] I send int: %d.\n", my_rank, intToSend);
            MPI_Ssend(&intToSend, 1, MPI_INT32_T, RECEIVER, 0, MPI_COMM_WORLD);
            break;
        }
        case RECEIVER:
        {
            // Receive the int
            int32_t intReceived;
            MPI_Recv(&intReceived, 1, MPI_INT32_T, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
            printf("[MPI process %d] I received int: %d.\n", my_rank, intReceived);
            break;
        }
    }

    MPI_Finalize();

    return EXIT_SUCCESS;
}

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#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>

/**
 * @brief Illustrate how to communicate an array of 4-byte ints between 2 MPI
 * processes.
 * @details This application is meant to be run with 2 MPI processes: 1 sender
 * and 1 receiver. The former sends an array of 4-byte ints to the latter, which
 * prints it.
 **/
int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    // Check that 2 MPI processes are used.
    int size;
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    if(size != 2)
    {
        printf("This application is meant to be run with 2 MPI processes.\n");
        MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
    }

    // Get my rank and do the corresponding job.
    enum role_ranks { SENDER, RECEIVER };
    int my_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
    switch(my_rank)
    {
        case SENDER:
        {
            // Send the ints
            int32_t intsToSend[2] = { 12345, 67890 };
            printf("[MPI process %d] I send ints: %d and %d.\n", my_rank, intsToSend[0], intsToSend[1]);
            MPI_Ssend(intsToSend, 2, MPI_INT32_T, RECEIVER, 0, MPI_COMM_WORLD);
            break;
        }
        case RECEIVER:
        {
            // Receive the ints
            int32_t intsReceived[2];
            MPI_Recv(intsReceived, 2, MPI_INT32_T, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
            printf("[MPI process %d] I received ints: %d and %d.\n", my_rank, intsReceived[0], intsReceived[1]);
            break;
        }
    }

    MPI_Finalize();

    return EXIT_SUCCESS;
}