[petsc-users] Cholesky: matrix ordering with aij? Bug with debugging=1 for ordering on sbaij?

[Eric Chamberland]

On 11/27/2014 02:22 PM, Barry Smith wrote:
>> When/where is the "matrix ordering: nd" used since it is documented to not works on sbaij matrix?
>
>     The factorization is done on the aij matrix and the result put into a sbaij matrix. Since with aij it is easy to reorder rows/columns it can do the factorization in any order it wants. sbaij only stores the upper half of the matrix so factorizing in any ordering besides "natural" is nasty and we don't do it.

ok!  So the assembled matrix is permuted then returned to it's original 
ordering or a temporary copy is made? (answer can point into the code)

>>
>> Is this the expected behavior?
>
>     Well kind of. When debugging is turned off the the error checking that an ordering is actually a permutation is turned off hence the code gets further (until it cannot do the factorization). Hence two different error messages.
>
>     Now I suspect that it is generating a bad ordering with the sbaij matrix so probably it would be best if we errored out in the MatGetOrdering() always. But even in the current situation nothing is really going wrong.
>
>    Barry

understood.

Thanks again!

Eric