[petsc-users] Problem in MatSetValues

[Eda Oktay]

Dear Matt,

Thank you for answering. First of all, sizeof(vals) returns to number of
entries, I checked. Secondly, I found a problem:

ncols gives me 6.95328e-310. However, I checked the matrix L, it was
computed properly.

Why can ncols give such a value?

Thanks,

Eda

Matthew Knepley <knepley at gmail.com>, 11 Mar 2019 Pzt, 15:56 tarihinde şunu
yazdı:

> 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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