Actual source code: ex22.c


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

  4: #include <petscvec.h>

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

 15:   PetscFunctionBeginUser;
 16:   PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
 17:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 18:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

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

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

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

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

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

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

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

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

 54:   PetscCall(PetscFinalize());
 55:   return 0;
 56: }

 58: /*TEST

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

 85: TEST*/