Actual source code: ex23.c

  1: /*$Id: ex23.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:   Using a blocked send and a strided receive.nn";

  6: /*
  7:         0 1 2 3 | 4 5 6 7 ||  8 9 10 11 

  9:      Scatter first and third block to first processor and 
 10:      second and third block to second processor
 11: */
 12:  #include petscvec.h
 13:  #include petscsys.h

 15: int main(int argc,char **argv)
 16: {
 17:   int           ierr,i;
 18:   int           size,rank,blocks[2],nlocal;
 19:   PetscScalar   value;
 20:   Vec           x,y;
 21:   IS            is1,is2;
 22:   VecScatter    ctx = 0;

 24:   PetscInitialize(&argc,&argv,(char*)0,help);
 25:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 26:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

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

 30:   /* create two vectors */
 31:   if (!rank) nlocal = 8;
 32:   else nlocal = 4;
 33:   VecCreate(PETSC_COMM_WORLD,&x);
 34:   VecSetSizes(x,nlocal,12);
 35:   VecSetFromOptions(x);
 36:   VecCreateSeq(PETSC_COMM_SELF,8,&y);

 38:   /* create two index sets */
 39:   if (!rank) {
 40:     blocks[0] = 0; blocks[1] = 8;
 41:   } else {
 42:     blocks[0] = 4; blocks[1] = 8;
 43:   }
 44:   ISCreateBlock(PETSC_COMM_SELF,4,2,blocks,&is1);
 45:   ISCreateStride(PETSC_COMM_SELF,8,0,1,&is2);

 47:   for (i=0; i<12; i++) {
 48:     value = i;
 49:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 50:   }
 51:   VecAssemblyBegin(x);
 52:   VecAssemblyEnd(x);

 54:   VecScatterCreate(x,is1,y,is2,&ctx);
 55:   VecScatterBegin(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
 56:   VecScatterEnd(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
 57:   VecScatterDestroy(ctx);
 58: 
 59:   PetscSleep(2*rank);
 60:   VecView(y,PETSC_VIEWER_STDOUT_SELF);

 62:   VecDestroy(x);
 63:   VecDestroy(y);
 64:   ISDestroy(is1);
 65:   ISDestroy(is2);

 67:   PetscFinalize();
 68:   return 0;
 69: }
 70: