Actual source code: ex12.c

petsc-3.12.1 2019-10-22
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  2: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
  3: This does case when we are merely selecting the local part of the\n\
  4: parallel vector.\n";

  6:  #include <petscvec.h>

  8: int main(int argc,char **argv)
  9: {
 11:   PetscMPIInt    size,rank;
 12:   PetscInt       n = 5,i;
 13:   PetscScalar    value;
 14:   Vec            x,y;
 15:   IS             is1,is2;
 16:   VecScatter     ctx = 0;

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

 20:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 23:   /* create two vectors */
 24:   VecCreate(PETSC_COMM_WORLD,&x);
 25:   VecSetSizes(x,PETSC_DECIDE,size*n);
 26:   VecSetFromOptions(x);
 27:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 29:   /* create two index sets */
 30:   ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
 31:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);

 33:   /* each processor inserts the entire vector */
 34:   /* this is redundant but tests assembly */
 35:   for (i=0; i<n; i++) {
 36:     value = (PetscScalar) (i + 10*rank);
 37:     VecSetValues(y,1,&i,&value,INSERT_VALUES);
 38:   }
 39:   VecAssemblyBegin(y);
 40:   VecAssemblyEnd(y);

 42:   VecScatterCreate(y,is2,x,is1,&ctx);
 43:   VecScatterBegin(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 44:   VecScatterEnd(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 45:   VecScatterDestroy(&ctx);

 47:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 49:   VecDestroy(&x);
 50:   VecDestroy(&y);
 51:   ISDestroy(&is1);
 52:   ISDestroy(&is2);

 54:   PetscFinalize();
 55:   return ierr;
 56: }



 60: /*TEST

 62:    test:
 63:       nsize: 2

 65: TEST*/