Actual source code: ex25.c

  1: /*$Id: ex25.c,v 1.14 2001/03/23 23:21:30 balay Exp $*/

  3: static char help[] = "Scatters from a parallel vector to a sequential vector.  Inn
  4: this case processor zero is as long as the entire parallel vector; rest are zero length.nn";

 6:  #include petscvec.h
 7:  #include petscsys.h

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

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

 22:   /* create two vectors */
 23:   N = size*n;
 24:   VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,N,&y);
 25:   if (!rank) {
 26:     VecCreateSeq(PETSC_COMM_SELF,N,&x);
 27:   } else {
 28:     VecCreateSeq(PETSC_COMM_SELF,0,&x);
 29:   }

 31:   /* create two index sets */
 32:   if (!rank) {
 33:     ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
 34:     ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
 35:   } else {
 36:     ISCreateStride(PETSC_COMM_SELF,0,0,1,&is1);
 37:     ISCreateStride(PETSC_COMM_SELF,0,0,1,&is2);
 38:   }

 40:   VecSet(&zero,x);
 41:   VecGetOwnershipRange(y,&low,&high);
 42:   for (i=0; i<n; i++) {
 43:     iglobal = i + low; value = (Scalar) (i + 10*rank);
 44:     VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
 45:   }
 46:   VecAssemblyBegin(y);
 47:   VecAssemblyEnd(y);
 48:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 50:   VecScatterCreate(y,is2,x,is1,&ctx);
 51:   VecScatterBegin(y,x,ADD_VALUES,SCATTER_FORWARD,ctx);
 52:   VecScatterEnd(y,x,ADD_VALUES,SCATTER_FORWARD,ctx);
 53:   VecScatterDestroy(ctx);
 54: 
 55:   if (!rank)
 56:     {printf("----n"); VecView(x,PETSC_VIEWER_STDOUT_SELF);}

 58:   VecDestroy(x);
 59:   VecDestroy(y);
 60:   ISDestroy(is1);
 61:   ISDestroy(is2);

 63:   PetscFinalize();
 64:   return 0;
 65: }
 66: