[petsc-users] Question about MatMultDiagonalBlock

[John Fettig]

On Sat, Oct 6, 2012 at 4:44 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> On Oct 5, 2012, at 7:38 PM, John Fettig <john.fettig at gmail.com> wrote:
>>What is wrong with the diagonal
>> block when inode.size==0?
>>
>> Thanks,
>> John
>
>    John,
>
>      When innode.size is zero the "diagonal blocks" are all 1 by 1.
...
>   Are you using MatMultDiagonalBlock() for some other case?


Barry,

Thanks for the explanation, it makes sense now. I was trying to use it
in the context of a multigrid, and didn't think about the coarse
level.  It must have been failing when the diagonal block was 1.  In
the end, though, I ended up not using this function.  I was just
curious why there should be any restriction.

John