Actual source code: ex9.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:   PetscInt       n = 5,i,idx2[3] = {0,2,3},idx1[3] = {0,1,2};
  9:   PetscMPIInt    size,rank;
 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,PETSC_DECIDE,size*n);
 22:   VecSetFromOptions(x);
 23:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 25:   /* create two index sets */
 26:   ISCreateGeneral(PETSC_COMM_SELF,3,idx1,PETSC_COPY_VALUES,&is1);
 27:   ISCreateGeneral(PETSC_COMM_SELF,3,idx2,PETSC_COPY_VALUES,&is2);

 29:   /* fill local part of parallel vector */
 30:   for (i=n*rank; i<n*(rank+1); i++) {
 31:     value = (PetscScalar) i;
 32:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 33:   }
 34:   VecAssemblyBegin(x);
 35:   VecAssemblyEnd(x);

 37:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 39:   VecSet(y,-1.0);

 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,"scattered vector\n");
 48:     VecView(y,PETSC_VIEWER_STDOUT_SELF);
 49:   }
 50:   ISDestroy(&is1);
 51:   ISDestroy(&is2);
 52:   VecDestroy(&x);
 53:   VecDestroy(&y);

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

 59: /*TEST

 61:    test:
 62:       nsize: 2

 64: TEST*/