[petsc-users] Problem in MatSetValues

[Matthew Knepley]

On Mon, Mar 11, 2019 at 8:27 AM Eda Oktay via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
> I have a following part of a code which tries to change the nonzero values
> of matrix L with -1. However in MatSetValues line, something happens and
> some of the values in matrix turns into 1.99665e-314 instead of -1. Type of
> arr is defined as PetscScalar and arr is produced correctly. What can be
> the problem, is there a mistake about types?
>
> Thanks,
>
> Eda
>
>
> for(rw = mm; rw<nn; ++rw){
>
>             ierr = MatGetRow(L,rw,&ncols,&cols,&vals);CHKERRQ(ierr);
>
>             s = sizeof(vals);
>

This is wrong. sizeof(vals) gives bytes, not entries. Why don't you just
use ncols here?

  Matt


>             ierr = PetscMalloc1(s,&arr);CHKERRQ(ierr);
>
>             for(j=0;j<s;++j){
>
>                 arr[j]=-1.0;
>             }
>             ierr =
> MatSetValues(NSymmA,1,&rw,ncols,cols,arr,INSERT_VALUES);CHKERRQ(ierr);
>             ierr = MatRestoreRow(L,rw,&ncols,&cols,&vals);CHKERRQ(ierr);
>         }
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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