Actual source code: ex11.c


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

  4: #include <petscvec.h>

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

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

 19:   /* create two vectors */
 20:   VecCreate(PETSC_COMM_WORLD,&x);
 21:   VecSetSizes(x,rank+1,PETSC_DECIDE);
 22:   VecSetFromOptions(x);
 23:   VecGetSize(x,&N);
 24:   VecCreateSeq(PETSC_COMM_SELF,N-rank,&y);

 26:   /* create two index sets */
 27:   ISCreateStride(PETSC_COMM_SELF,N-rank,rank,1,&is1);
 28:   ISCreateStride(PETSC_COMM_SELF,N-rank,0,1,&is2);

 30:   /* fill parallel vector: note this is not efficient way*/
 31:   for (i=0; i<N; i++) {
 32:     value = (PetscScalar) i;
 33:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 34:   }
 35:   VecAssemblyBegin(x);
 36:   VecAssemblyEnd(x);
 37:   VecSet(y,-1.0);

 39:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

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

 46:   if (rank == 0) {
 47:     PetscPrintf(PETSC_COMM_SELF,"----\n");
 48:     VecView(y,PETSC_VIEWER_STDOUT_SELF);
 49:   }

 51:   ISDestroy(&is1);
 52:   ISDestroy(&is2);
 53:   VecDestroy(&x);
 54:   VecDestroy(&y);

 56:   PetscFinalize();
 57:   return 0;
 58: }

 60: /*TEST

 62:    test:
 63:       nsize: 2

 65:    test:
 66:       suffix: bts
 67:       nsize: 2
 68:       args: -vec_assembly_legacy
 69:       output_file: output/ex11_1.out

 71: TEST*/