[petsc-dev] petsc-dev: ASM with sbaij matrix and block size=1 broken?

[Brad Aagaard]

On 11/5/11 10:25 AM, Jed Brown wrote:
> On Sat, Nov 5, 2011 at 11:13, Brad Aagaard <baagaard at usgs.gov
> <mailto:baagaard at usgs.gov>> wrote:
>
>     The error is in our inner solve (associated with computing the
>     adjustment to the solution based on the friction criterion) for
>     cases where not all processors have points on the fault. On
>     processors without points on the fault the block size is -1 and the
>     local size is 0. For processors with points on the fault, the block
>     size is 3.
>
>
> How is this happening? MatSetBlockSize_MPISBAIJ raises an error if you
> try to change the block size. Are you messing with the PetscLayout
> directly or something?
>
>
>     I tried altering DMMeshCreateMatrix so that it uses a block size of
>     1 if bs==-1, but I still get the error. Does the block size need to
>     be consistent across all processors, even those a local size of 0?
>     Alternatively, is the local size of 0 causing problems?
>
>
> Yes, bs must be the same.
>
> Since bs must be set for PetscLayoutSetUp() to succeed, the fact that
> you have bs=-1 means that function wasn't called. It could be memory
> corruption or it could be some manual fiddling with the PetscLayout.
> Somehow, you have bypassed several guards in the code that are supposed
> to cause errors with invalid input like this.
>
> The local size of 0 should not cause a problem.

It looks like Matt is calling Sieve layout stuff in 
DMMeshCreateMatrix(). I don't see any calls to MatSetBlockSize.

Brad