Actual source code: ex14.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 the tricky case.\n\n";

  5:  #include <petscvec.h>

  7: int main(int argc,char **argv)
  8: {
 10:   PetscInt       n = 5,N;
 11:   PetscMPIInt    size,rank;
 12:   PetscScalar    value,zero = 0.0;
 13:   Vec            x,y;
 14:   IS             is1,is2;
 15:   VecScatter     ctx = 0;

 17:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
 18:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 19:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

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

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

 32:   value = rank+1;
 33:   VecSet(x,value);
 34:   VecSet(y,zero);

 36:   VecScatterCreate(x,is1,y,is2,&ctx);
 37:   VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 38:   VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 39:   VecScatterDestroy(&ctx);

 41:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 43:   VecDestroy(&x);
 44:   VecDestroy(&y);
 45:   ISDestroy(&is1);
 46:   ISDestroy(&is2);

 48:   PetscFinalize();
 49:   return ierr;
 50: }



 54: /*TEST

 56:    test:
 57:       nsize: 2

 59: TEST*/