Actual source code: ex22.c

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

 4:  #include petscvec.h
 5:  #include petscsys.h

  9: int main(int argc,char **argv)
 10: {
 12:   PetscInt       n = 5,N,i;
 13:   PetscMPIInt    size,rank;
 14:   PetscScalar    value,zero = 0.0;
 15:   Vec            x,y;
 16:   IS             is1,is2;
 17:   VecScatter     ctx = 0;

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

 23:   /* create two vectors */
 24:   N = size*n;
 25:   VecCreate(PETSC_COMM_WORLD,&y);
 26:   VecSetSizes(y,n,PETSC_DECIDE);CHKERRQ(ierr)
 27:   VecSetFromOptions(y);

 29:   VecCreate(PETSC_COMM_WORLD,&x);
 30:   VecSetSizes(x,n,PETSC_DECIDE);
 31:   VecSetFromOptions(x);

 33:   /* create two index sets */
 34:   ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
 35:   ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);

 37:   /* fill local part of parallel vector x */
 38:   value = (PetscScalar)(rank+1);
 39:   for (i=n*rank; i<n*(rank+1); i++) {
 40:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 41:   }
 42:   VecAssemblyBegin(x);
 43:   VecAssemblyEnd(x);

 45:   VecSet(y,zero);

 47:   VecScatterCreate(x,is1,y,is2,&ctx);
 48:   VecScatterBegin(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 49:   VecScatterEnd(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 50:   VecScatterDestroy(ctx);
 51: 
 52:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 54:   VecDestroy(x);
 55:   VecDestroy(y);
 56:   ISDestroy(is1);
 57:   ISDestroy(is2);

 59:   PetscFinalize();
 60:   return 0;
 61: }
 62: