Actual source code: ex22.c

petsc-3.9.1 2018-04-29
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  2: static char help[] = "Scatters from a parallel vector to a parallel vector.\n\n";

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

  8:  #include <petscvec.h>

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

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

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

 30:   VecCreate(PETSC_COMM_WORLD,&x);
 31:   VecSetSizes(x,n,PETSC_DECIDE);
 32:   VecSetFromOptions(x);

 34:   /* create two index sets */
 35:   ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
 36:   ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);

 38:   /* fill local part of parallel vector x */
 39:   value = (PetscScalar)(rank+1);
 40:   for (i=n*rank; i<n*(rank+1); i++) {
 41:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 42:   }
 43:   VecAssemblyBegin(x);
 44:   VecAssemblyEnd(x);

 46:   VecSet(y,zero);

 48:   VecScatterCreate(x,is1,y,is2,&ctx);
 49:   VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 50:   VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 51:   VecScatterDestroy(&ctx);

 53:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 55:   VecDestroy(&x);
 56:   VecDestroy(&y);
 57:   ISDestroy(&is1);
 58:   ISDestroy(&is2);

 60:   PetscFinalize();
 61:   return ierr;
 62: }



 66: /*TEST

 68:    test:
 69:       nsize: 4

 71: TEST*/