The Great and Terrible implementation of MPI-2

function index


Free an MPI RMA window
int MPI_Win_free(
  MPI_Win *win


[in] window object (handle)


Frees the window object win and returns a null handle (equal to MPI_WIN_NULL). This is a collective call executed by all processes in the group associated with win. MPI_WIN_FREE(win) can be invoked by a process only after it has completed its involvement in RMA communications on window win: i.e., the process has called MPI_WIN_FENCE, or called MPI_WIN_WAIT to match a previous call to MPI_WIN_POST or called MPI_WIN_COMPLETE to match a previous call to MPI_WIN_START or called MPI_WIN_UNLOCK to match a previous call to MPI_WIN_LOCK. When the call returns, the window memory can be freed.

If successfully freed, win is set to MPI_WIN_NULL.

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

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


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.

No error; MPI routine completed successfully.
Invalid MPI window object

Example Code

The following sample code illustrates MPI_Win_free.

#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;
if (nprocs != 2) {
        printf("Run this program with 2 processes\n");fflush(stdout);
    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);
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);
    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);

        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);
return errs;