int MPI_Win_post(
  MPI_Group group,
  int assert,
  MPI_Win win
);

Parameters

group

[in] group of origin processes (handle)

assert

[in] Used to optimize this call; zero may be used as a default. See notes. (integer)

win

[in] window object (handle)

Remarks

Starts an RMA exposure epoch for the local window associated with win. Only processes in group should access the window with RMA calls on win during this epoch. Each process in group must issue a matching call to MPI_WIN_START. MPI_WIN_POST does not block.

MPI_MODE_NOCHECK

the matching calls to MPI_WIN_START have not yet occurred on any origin processes when the call to MPI_WIN_POST is made. The nocheck option can be specified by a post call if and only if it is specified by each matching start call.

MPI_MODE_NOSTORE

the local window was not updated by local stores (or local get or receive calls) since last synchronization. This may avoid the need for cache synchronization at the post call.

MPI_MODE_NOPUT

the local window will not be updated by put or accumulate calls after the post call, until the ensuing (wait) synchronization. This may avoid the need for cache synchronization at the wait call.

Notes for Fortran

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS

No error; MPI routine completed successfully.

Example Code

The following sample code illustrates MPI_Win_post.

#include "mpi.h"
#include "stdio.h"
 
/* tests put and get with post/start/complete/wait on 2 processes */
 
#define SIZE1 100
#define SIZE2 200
 
int main(int argc, char *argv[])
{
    int rank, destrank, nprocs, *A, *B, i;
    MPI_Group comm_group, group;
    MPI_Win win;
    int errs = 0;
 
    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&rank);
    if (nprocs != 2) {
        printf("Run this program with 2 processes\n");fflush(stdout);
        MPI_Abort(MPI_COMM_WORLD,1);
    }
 
    i = MPI_Alloc_mem(SIZE2 * sizeof(int), MPI_INFO_NULL, &A);
    if (i) {
        printf("Can't allocate memory in test program\n");fflush(stdout);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }
    i = MPI_Alloc_mem(SIZE2 * sizeof(int), MPI_INFO_NULL, &B);
    if (i) {
        printf("Can't allocate memory in test program\n");fflush(stdout);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    MPI_Comm_group(MPI_COMM_WORLD, &comm_group);
 
    if (rank == 0) {
        for (i=0; i<SIZE2; i++) A[i] = B[i] = i;
        MPI_Win_create(NULL, 0, 1, MPI_INFO_NULL, MPI_COMM_WORLD, &win);
        destrank = 1;
        MPI_Group_incl(comm_group, 1, &destrank, &group);
        MPI_Win_start(group, 0, win);
        for (i=0; i<SIZE1; i++)
            MPI_Put(A+i, 1, MPI_INT, 1, i, 1, MPI_INT, win);
        for (i=0; i<SIZE1; i++)
            MPI_Get(B+i, 1, MPI_INT, 1, SIZE1+i, 1, MPI_INT, win);
 
        MPI_Win_complete(win);
 
        for (i=0; i<SIZE1; i++)
            if (B[i] != (-4)*(i+SIZE1)) {
                printf("Get Error: B[i] is %d, should be %d\n", B[i], (-4)*(i+SIZE1));fflush(stdout);
                errs++;
            }
    }
    else { /* rank=1 */
        for (i=0; i<SIZE2; i++) B[i] = (-4)*i;
        MPI_Win_create(B, SIZE2*sizeof(int), sizeof(int), MPI_INFO_NULL, MPI_COMM_WORLD, &win);
        destrank = 0;
        MPI_Group_incl(comm_group, 1, &destrank, &group);
        MPI_Win_post(group, 0, win);
        MPI_Win_wait(win);

        for (i=0; i<SIZE1; i++) {
            if (B[i] != i) {
                printf("Put Error: B[i] is %d, should be %d\n", B[i], i);fflush(stdout);
                errs++;
            }
        }
    }
 
    MPI_Group_free(&group);
    MPI_Group_free(&comm_group);
    MPI_Win_free(&win);
    MPI_Free_mem(A);
    MPI_Free_mem(B);
 
    MPI_Finalize();
    return errs;
}