MPI_Win | RookieHPC

Definition

MPI_Win is the data structure representing windows that are used to expose memory regions with which MPI processes can interact one-sidedly. MPI windows are created with MPI_Win_create, MPI_Win_create_dynamic, MPI_Win_allocate or MPI_Win_allocate_shared. MPI windows are then destroyed with MPI_Win_free.

Example

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

/**
 * @brief Illustrate how to use the MPI_Win data structure.
 * @details This application consists in creating a window and destroying it.
 **/
int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    // Check that only 2 MPI processes are spawn
    int comm_size;
    MPI_Comm_size(MPI_COMM_WORLD, &comm_size);
    if(comm_size != 2)
    {
        printf("This application is meant to be run with 2 MPI processes, not %d.\n", comm_size);
        MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
    }

    // Get my rank
    int my_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    // Create the window
    const int ARRAY_SIZE = 2;
    int* window_buffer;
    MPI_Win window;
    MPI_Win_allocate(ARRAY_SIZE * sizeof(int), sizeof(int), MPI_INFO_NULL, MPI_COMM_WORLD, &window_buffer, &window);
    printf("[MPI process %d] Window created.\n", my_rank);

    // Issue RMA communications
    // ...
    // Wait for all RMA communications to complete

    // Destroy the window
    printf("[MPI process %d] Window destroyed.\n", my_rank);
    MPI_Win_free(&window);

    MPI_Finalize();

    return EXIT_SUCCESS;
}