Actual source code: ex24.c

petsc-3.9.0 2018-04-07
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  2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
  3: Tests where the local part of the scatter is a copy.\n\n";

  5: /*T
  6:    requires: x
  7: T*/

  9:  #include <petscvec.h>

 11: int main(int argc,char **argv)
 12: {
 14:   PetscMPIInt    size,rank;
 15:   PetscInt       n = 5,i,*blks,bs = 1,m = 2;
 16:   PetscScalar    value;
 17:   Vec            x,y;
 18:   IS             is1,is2;
 19:   VecScatter     ctx = 0;
 20:   PetscViewer    sviewer;

 22:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

 24:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 25:   PetscOptionsGetInt(NULL,NULL,"-bs",&bs,NULL);

 27:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 28:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

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

 35:   /* create two index sets */
 36:   if (rank < size-1) m = n + 2;
 37:   else m = n;

 39:   PetscMalloc1(m,&blks);
 40:   blks[0] = n*rank;
 41:   for (i=1; i<m; i++) blks[i] = blks[i-1] + 1;
 42:   ISCreateBlock(PETSC_COMM_SELF,bs,m,blks,PETSC_COPY_VALUES,&is1);
 43:   PetscFree(blks);

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

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

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

 62:   PetscViewerASCIIPushSynchronized(PETSC_VIEWER_STDOUT_WORLD);
 63:   PetscViewerASCIISynchronizedPrintf(PETSC_VIEWER_STDOUT_WORLD,"----\n");
 64:   PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&sviewer);
 65:   VecView(y,sviewer); fflush(stdout);
 66:   PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&sviewer);
 67:   PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
 68:   PetscViewerASCIIPopSynchronized(PETSC_VIEWER_STDOUT_WORLD);

 70:   VecScatterDestroy(&ctx);

 72:   VecDestroy(&x);
 73:   VecDestroy(&y);
 74:   ISDestroy(&is1);
 75:   ISDestroy(&is2);

 77:   PetscFinalize();
 78:   return ierr;
 79: }



 83: /*TEST

 85:    test:
 86:       nsize: 3

 88: TEST*/