Actual source code: ex10.c

  1: /*$Id: ex10.c,v 1.20 2001/09/11 16:32:10 bsmith Exp $*/

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

 6:  #include petsc.h
 7:  #include petscis.h
 8:  #include petscvec.h
 9:  #include petscsys.h

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

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

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

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

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

 35:   /* create two index sets */
 36:   for (i=0; i<3; i++) {
 37:     ix0[i] *= bs; ix1[i] *= bs;
 38:     iy0[i] *= bs; iy1[i] *= bs;
 39:   }

 41:   if (!rank) {
 42:     ISCreateBlock(PETSC_COMM_SELF,bs,3,ix0,&isx);
 43:     ISCreateBlock(PETSC_COMM_SELF,bs,3,iy0,&isy);
 44:   } else {
 45:     ISCreateBlock(PETSC_COMM_SELF,bs,3,ix1,&isx);
 46:     ISCreateBlock(PETSC_COMM_SELF,bs,3,iy1,&isy);
 47:   }

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

 57:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

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


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

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

 76:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

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

 83:   PetscFinalize();
 84:   return 0;
 85: }
 86: