Actual source code: ex22.c

  1: static char help[] = "Scatters from a parallel vector to a parallel vector.\n\n";

  3: #include <petscvec.h>

  5: int main(int argc, char **argv)
  6: {
  7:   PetscInt    n = 5, N, i;
  8:   PetscMPIInt size, rank;
  9:   PetscScalar value, zero = 0.0;
 10:   Vec         x, y;
 11:   IS          is1, is2;
 12:   VecScatter  ctx = 0;

 14:   PetscFunctionBeginUser;
 15:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
 16:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 17:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

 19:   /* create two vectors */
 20:   N = size * n;
 21:   PetscCall(VecCreate(PETSC_COMM_WORLD, &y));
 22:   PetscCall(VecSetSizes(y, n, PETSC_DECIDE));
 23:   PetscCall(VecSetFromOptions(y));

 25:   PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
 26:   PetscCall(VecSetSizes(x, n, PETSC_DECIDE));
 27:   PetscCall(VecSetFromOptions(x));

 29:   /* create two index sets */
 30:   PetscCall(ISCreateStride(PETSC_COMM_WORLD, n, n * rank, 1, &is1));
 31:   PetscCall(ISCreateStride(PETSC_COMM_WORLD, n, (n * (rank + 1)) % N, 1, &is2));

 33:   /* fill local part of parallel vector x */
 34:   value = (PetscScalar)(rank + 1);
 35:   for (i = n * rank; i < n * (rank + 1); i++) PetscCall(VecSetValues(x, 1, &i, &value, INSERT_VALUES));
 36:   PetscCall(VecAssemblyBegin(x));
 37:   PetscCall(VecAssemblyEnd(x));

 39:   PetscCall(VecSet(y, zero));

 41:   PetscCall(VecScatterCreate(x, is1, y, is2, &ctx));
 42:   PetscCall(VecScatterBegin(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
 43:   PetscCall(VecScatterEnd(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
 44:   PetscCall(VecScatterDestroy(&ctx));

 46:   PetscCall(VecView(y, PETSC_VIEWER_STDOUT_WORLD));

 48:   PetscCall(VecDestroy(&x));
 49:   PetscCall(VecDestroy(&y));
 50:   PetscCall(ISDestroy(&is1));
 51:   PetscCall(ISDestroy(&is2));

 53:   PetscCall(PetscFinalize());
 54:   return 0;
 55: }

 57: /*TEST

 59:    testset:
 60:       nsize: 4
 61:       output_file: output/ex22_1.out
 62:       filter: grep -v "  type:"
 63:       diff_args: -j
 64:       test:
 65:         suffix: standard
 66:         args: -vec_type standard
 67:       test:
 68:         requires: cuda
 69:         suffix: cuda
 70:         args: -vec_type cuda
 71:       test:
 72:         requires: viennacl
 73:         suffix: viennacl
 74:         args: -vec_type viennacl
 75:       test:
 76:         requires: kokkos_kernels
 77:         suffix: kokkos
 78:         args: -vec_type kokkos
 79:       test:
 80:         requires: hip
 81:         suffix: hip
 82:         args: -vec_type hip

 84: TEST*/