Actual source code: ex23.c

petsc-3.10.5 2019-03-28
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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: */
 11: /*T
 12:    requires: x
 13: T*/

 15:  #include <petscvec.h>

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

 28:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
 29:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 30:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

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

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

 44:   /* create two index sets */
 45:   if (!rank) {
 46:     blocks[0] = 0; blocks[1] = 2;
 47:   } else {
 48:     blocks[0] = 1; blocks[1] = 2;
 49:   }
 50:   ISCreateBlock(PETSC_COMM_SELF,4,2,blocks,PETSC_COPY_VALUES,&is1);
 51:   ISCreateStride(PETSC_COMM_SELF,8,0,1,&is2);

 53:   for (i=0; i<12; i++) {
 54:     value = i;
 55:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 56:   }
 57:   VecAssemblyBegin(x);
 58:   VecAssemblyEnd(x);

 60:   VecScatterCreate(x,is1,y,is2,&ctx);
 61:   VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 62:   VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 63:   VecScatterDestroy(&ctx);

 65:   PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer);
 66:   VecView(y,subviewer);
 67:   PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer);

 69:   VecDestroy(&x);
 70:   VecDestroy(&y);
 71:   ISDestroy(&is1);
 72:   ISDestroy(&is2);

 74:   PetscFinalize();
 75:   return ierr;
 76: }



 80: /*TEST

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