[petsc-users] A question of VecSetValues

[Hong Zhang]

Yonghui :
...
  ierr = VecSet(x,one);CHKERRQ(ierr);  // set x= [ 1, 1, 1, 1, 1, 1]

RANK 0:
do 100 i=0,N-1  (N=6)
                ^
         call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
100  continue
//  x = [2, 2, 2, 2, 2, 2]

RANK 1:
do 100 i=0,N-2
                ^
         call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
100  continue
// x = [3, 3, 3, 3, 3, 2]

RANK 2:
do 100 i=0,N-3
                ^
         call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
100  continue
// x = [4, 4, 4, 4, 3, 2]

Hong

> Dear PESTc users,
>
>
>
> I don’t understand VecSetValues very well. I compiled ex2 and run with
> mpiexec –n 3. I got result like this:
>
>
>
> Vector Object: 3 MPI processes
>
>   type: mpi
>
> Process [0]
>
> 4
>
> Process [1]
>
> 4
>
> 4
>
> Process [2]
>
> 4
>
> 3
>
> 2
>
>
>
> Here is how I am comfused:
>
> RANK 0:
>
> do 100 i=0,0
>
>          call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
>
> 100  continue
>
>
>
> RANK 1:
>
> do 100 i=0,1
>
>          call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
>
> 100  continue
>
>
>
> RANK 2:
>
> do 100 i=0,2
>
>          call VecSetValues(x,1,i,1,ADD_VALUES,ierr)
>
> 100  continue
>
>
>
> I don’t see any clue for getting the result above. Please show me how it
> works! Thanks.