Actual source code: ex10.c

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

 5:  #include petscvec.h

  9: int main(int argc,char **argv)
 10: {
 12:   PetscInt       bs = 1,n = 5,ix0[3] = {5,7,9},ix1[3] = {2,3,4},i,iy0[3] = {1,2,4},iy1[3] = {0,1,3};
 13:   PetscMPIInt    size,rank;
 14:   PetscScalar    value;
 15:   Vec            x,y;
 16:   IS             isx,isy;
 17:   VecScatter     ctx = 0,newctx;

 19:   PetscInitialize(&argc,&argv,(char*)0,help);
 20:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

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

 25:   PetscOptionsGetInt(PETSC_NULL,"-bs",&bs,PETSC_NULL);
 26:   n = bs*n;

 28:   /* create two vectors */
 29:   VecCreate(PETSC_COMM_WORLD,&x);
 30:   VecSetSizes(x,PETSC_DECIDE,size*n);
 31:   VecSetFromOptions(x);
 32:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 34:   /* create two index sets */
 35:   for (i=0; i<3; i++) {
 36:     ix0[i] *= bs; ix1[i] *= bs;
 37:     iy0[i] *= bs; iy1[i] *= bs;
 38:   }

 40:   if (!rank) {
 41:     ISCreateBlock(PETSC_COMM_SELF,bs,3,ix0,&isx);
 42:     ISCreateBlock(PETSC_COMM_SELF,bs,3,iy0,&isy);
 43:   } else {
 44:     ISCreateBlock(PETSC_COMM_SELF,bs,3,ix1,&isx);
 45:     ISCreateBlock(PETSC_COMM_SELF,bs,3,iy1,&isy);
 46:   }

 48:   /* fill local part of parallel vector */
 49:   for (i=n*rank; i<n*(rank+1); i++) {
 50:     value = (PetscScalar) i;
 51:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 52:   }
 53:   VecAssemblyBegin(x);
 54:   VecAssemblyEnd(x);

 56:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 58:   /* fill local part of parallel vector */
 59:   for (i=0; i<n; i++) {
 60:     value = -(PetscScalar) (i + 100*rank);
 61:     VecSetValues(y,1,&i,&value,INSERT_VALUES);
 62:   }
 63:   VecAssemblyBegin(y);
 64:   VecAssemblyEnd(y);


 67:   VecScatterCreate(x,isx,y,isy,&ctx);
 68:   VecScatterCopy(ctx,&newctx);
 69:   VecScatterDestroy(ctx);

 71:   VecScatterBegin(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
 72:   VecScatterEnd(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
 73:   VecScatterDestroy(newctx);

 75:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 77:   ISDestroy(isx);
 78:   ISDestroy(isy);
 79:   VecDestroy(x);
 80:   VecDestroy(y);

 82:   PetscFinalize();
 83:   return 0;
 84: }
 85: