Actual source code: ex13.c


  2: static char help[] = "Scatters from a sequential vector to a parallel vector. \n\
  3: uses block index sets\n\n";

  5: #include <petscvec.h>

  7: int main(int argc, char **argv)
  8: {
  9:   PetscInt     bs = 1, n = 5, i, low;
 10:   PetscInt     ix0[3] = {5, 7, 9}, iy0[3] = {1, 2, 4}, ix1[3] = {2, 3, 4}, iy1[3] = {0, 1, 3};
 11:   PetscMPIInt  size, rank;
 12:   PetscScalar *array;
 13:   Vec          x, y;
 14:   IS           isx, isy;
 15:   VecScatter   ctx;
 16:   PetscViewer  sviewer;

 18:   PetscFunctionBeginUser;
 19:   PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
 20:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 21:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

 23:   PetscCheck(size >= 2, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Must run more than one processor");

 25:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-bs", &bs, NULL));
 26:   n = bs * n;

 28:   /* Create vector x over shared memory */
 29:   PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
 30:   PetscCall(VecSetSizes(x, n, PETSC_DECIDE));
 31:   PetscCall(VecSetFromOptions(x));

 33:   PetscCall(VecGetOwnershipRange(x, &low, NULL));
 34:   PetscCall(VecGetArray(x, &array));
 35:   for (i = 0; i < n; i++) array[i] = (PetscScalar)(i + low);
 36:   PetscCall(VecRestoreArray(x, &array));

 38:   /* Create a sequential vector y */
 39:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
 40:   PetscCall(VecGetArray(y, &array));
 41:   for (i = 0; i < n; i++) array[i] = (PetscScalar)(i + 100 * rank);
 42:   PetscCall(VecRestoreArray(y, &array));

 44:   /* Create two index sets */
 45:   if (rank == 0) {
 46:     PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, ix0, PETSC_COPY_VALUES, &isx));
 47:     PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, iy0, PETSC_COPY_VALUES, &isy));
 48:   } else {
 49:     PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, ix1, PETSC_COPY_VALUES, &isx));
 50:     PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, iy1, PETSC_COPY_VALUES, &isy));
 51:   }

 53:   if (rank == 10) {
 54:     PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n[%d] isx:\n", rank));
 55:     PetscCall(ISView(isx, PETSC_VIEWER_STDOUT_SELF));
 56:   }

 58:   PetscCall(VecScatterCreate(y, isy, x, isx, &ctx));
 59:   PetscCall(VecScatterSetFromOptions(ctx));

 61:   /* Test forward vecscatter */
 62:   PetscCall(VecSet(x, 0.0));
 63:   PetscCall(VecScatterBegin(ctx, y, x, ADD_VALUES, SCATTER_FORWARD));
 64:   PetscCall(VecScatterEnd(ctx, y, x, ADD_VALUES, SCATTER_FORWARD));
 65:   PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));

 67:   /* Test reverse vecscatter */
 68:   PetscCall(VecScale(x, -1.0));
 69:   PetscCall(VecScatterBegin(ctx, x, y, ADD_VALUES, SCATTER_REVERSE));
 70:   PetscCall(VecScatterEnd(ctx, x, y, ADD_VALUES, SCATTER_REVERSE));
 71:   PetscCall(PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD, PETSC_COMM_SELF, &sviewer));
 72:   if (rank == 1) PetscCall(VecView(y, sviewer));
 73:   PetscCall(PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD, PETSC_COMM_SELF, &sviewer));

 75:   /* Free spaces */
 76:   PetscCall(VecScatterDestroy(&ctx));
 77:   PetscCall(ISDestroy(&isx));
 78:   PetscCall(ISDestroy(&isy));
 79:   PetscCall(VecDestroy(&x));
 80:   PetscCall(VecDestroy(&y));
 81:   PetscCall(PetscFinalize());
 82:   return 0;
 83: }

 85: /*TEST

 87:    test:
 88:       nsize: 3

 90: TEST*/