Actual source code: ex23.c

petsc-3.12.2 2019-11-22
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  2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
  3:   Using a blocked send and a strided receive.\n\n";

  5: /*
  6:         0 1 2 3 | 4 5 6 7 ||  8 9 10 11

  8:      Scatter first and third block to first processor and
  9:      second and third block to second processor
 10: */

 12:  #include <petscvec.h>

 14: int main(int argc,char **argv)
 15: {
 17:   PetscInt       i,blocks[2],nlocal;
 18:   PetscMPIInt    size,rank;
 19:   PetscScalar    value;
 20:   Vec            x,y;
 21:   IS             is1,is2;
 22:   VecScatter     ctx = 0;
 23:   PetscViewer    subviewer;

 25:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
 26:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 27:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 29:   if (size != 2) SETERRQ(PETSC_COMM_SELF,1,"Must run with 2 processors");

 31:   /* create two vectors */
 32:   if (!rank) nlocal = 8;
 33:   else nlocal = 4;
 34:   VecCreate(PETSC_COMM_WORLD,&x);
 35:   VecSetSizes(x,nlocal,12);
 36:   VecSetFromOptions(x);
 37:   VecCreate(PETSC_COMM_SELF,&y);
 38:   VecSetSizes(y,8,PETSC_DECIDE);
 39:   VecSetFromOptions(y);

 41:   /* create two index sets */
 42:   if (!rank) {
 43:     blocks[0] = 0; blocks[1] = 2;
 44:   } else {
 45:     blocks[0] = 1; blocks[1] = 2;
 46:   }
 47:   ISCreateBlock(PETSC_COMM_SELF,4,2,blocks,PETSC_COPY_VALUES,&is1);
 48:   ISCreateStride(PETSC_COMM_SELF,8,0,1,&is2);

 50:   for (i=0; i<12; i++) {
 51:     value = i;
 52:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 53:   }
 54:   VecAssemblyBegin(x);
 55:   VecAssemblyEnd(x);

 57:   VecScatterCreate(x,is1,y,is2,&ctx);
 58:   VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 59:   VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 60:   VecScatterDestroy(&ctx);

 62:   PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer);
 63:   VecView(y,subviewer);
 64:   PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer);

 66:   VecDestroy(&x);
 67:   VecDestroy(&y);
 68:   ISDestroy(&is1);
 69:   ISDestroy(&is2);

 71:   PetscFinalize();
 72:   return ierr;
 73: }



 77: /*TEST

 79:    testset:
 80:       nsize: 2
 81:       output_file: output/ex23_1.out
 82:       filter: grep -v "  type:"
 83:       test:
 84:         suffix: standard
 85:         args: -vec_type standard
 86:       test:
 87:         requires: cuda
 88:         suffix: cuda
 89:         args: -vec_type cuda
 90:       test:
 91:         requires: viennacl
 92:         suffix:  viennacl
 93:         args: -vec_type viennacl
 94: TEST*/