Actual source code: ex14.c

petsc-3.9.2 2018-05-20
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  2: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
  3: This does the tricky case.\n\n";

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

  9:  #include <petscvec.h>

 11: int main(int argc,char **argv)
 12: {
 14:   PetscInt       n = 5,N;
 15:   PetscMPIInt    size,rank;
 16:   PetscScalar    value,zero = 0.0;
 17:   Vec            x,y;
 18:   IS             is1,is2;
 19:   VecScatter     ctx = 0;

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

 25:   /* create two vectors */
 26:   N    = size*n;
 27:   VecCreate(PETSC_COMM_WORLD,&y);
 28:   VecSetSizes(y,PETSC_DECIDE,N);
 29:   VecSetFromOptions(y);
 30:   VecCreateSeq(PETSC_COMM_SELF,N,&x);

 32:   /* create two index sets */
 33:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is1);
 34:   ISCreateStride(PETSC_COMM_SELF,n,rank,1,&is2);

 36:   value = rank+1;
 37:   VecSet(x,value);
 38:   VecSet(y,zero);

 40:   VecScatterCreate(x,is1,y,is2,&ctx);
 41:   VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 42:   VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 43:   VecScatterDestroy(&ctx);

 45:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 47:   VecDestroy(&x);
 48:   VecDestroy(&y);
 49:   ISDestroy(&is1);
 50:   ISDestroy(&is2);

 52:   PetscFinalize();
 53:   return ierr;
 54: }



 58: /*TEST

 60:    test:
 61:       nsize: 2

 63: TEST*/