Actual source code: ex24.c

  1: /*$Id: ex24.c,v 1.19 2001/04/10 19:35:02 bsmith Exp $*/

  3: static char help[] = "Scatters from a parallel vector to a sequential vector.n
  4: Tests where the local part of the scatter is a copy.nn";

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

  9: int main(int argc,char **argv)
 10: {
 11:   int           n = 5,ierr,size,rank,i,*blks,bs = 1,m = 2;
 12:   Scalar        value;
 13:   Vec           x,y;
 14:   IS            is1,is2;
 15:   VecScatter    ctx = 0;
 16:   PetscViewer   sviewer;

 18:   PetscInitialize(&argc,&argv,(char*)0,help);

 20:   PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
 21:   PetscOptionsGetInt(PETSC_NULL,"-bs",&bs,PETSC_NULL);

 23:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 24:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 26:   /* create two vectors */
 27:   VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,size*bs*n,&x);

 29:   /* create two index sets */
 30:   if (rank < size-1) {
 31:     m = n + 2;
 32:   } else {
 33:     m = n;
 34:   }
 35:   PetscMalloc((m)*sizeof(int),&blks);
 36:   blks[0] = n*rank*bs;
 37:   for (i=1; i<m; i++) {
 38:     blks[i] = blks[i-1] + bs;
 39:   }
 40:   ISCreateBlock(PETSC_COMM_SELF,bs,m,blks,&is1);
 41:   PetscFree(blks);

 43:   VecCreateSeq(PETSC_COMM_SELF,bs*m,&y);
 44:   ISCreateStride(PETSC_COMM_SELF,bs*m,0,1,&is2);

 46:   /* each processor inserts the entire vector */
 47:   /* this is redundant but tests assembly */
 48:   for (i=0; i<bs*n*size; i++) {
 49:     value = (Scalar) i;
 50:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 51:   }
 52:   VecAssemblyBegin(x);
 53:   VecAssemblyEnd(x);
 54:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 56:   VecScatterCreate(x,is1,y,is2,&ctx);
 57:   VecScatterBegin(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
 58:   VecScatterEnd(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);

 60:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"----n");
 61:   PetscViewerGetSingleton(PETSC_VIEWER_STDOUT_WORLD,&sviewer);
 62:   VecView(y,sviewer); fflush(stdout);
 63:   PetscViewerRestoreSingleton(PETSC_VIEWER_STDOUT_WORLD,&sviewer);
 64:   PetscSynchronizedFlush(PETSC_COMM_WORLD);

 66:   VecScatterDestroy(ctx);

 68:   VecDestroy(x);
 69:   VecDestroy(y);
 70:   ISDestroy(is1);
 71:   ISDestroy(is2);

 73:   PetscFinalize();
 74:   return 0;
 75: }
 76: