Actual source code: ex17.c


  2: static char help[] = "Scatters from a parallel vector to a sequential vector.  In\n\
  3: this case each local vector is as long as the entire parallel vector.\n\n";

  5: #include <petscvec.h>

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

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

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

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

 31:   VecSet(x,zero);
 32:   VecGetOwnershipRange(y,&low,&high);
 33:   for (i=0; i<n; i++) {
 34:     iglobal = i + low; value = (PetscScalar) (i + 10*rank);
 35:     VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
 36:   }
 37:   VecAssemblyBegin(y);
 38:   VecAssemblyEnd(y);
 39:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

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

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

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

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

 60: /*TEST

 62:    test:
 63:       nsize: 2

 65: TEST*/