[petsc-dev] Error with ML preconditioner

[Jed Brown]

Hmm, this debugging check was added by Mark here.

https://bitbucket.org/petsc/petsc-dev/commits/fb7e4343253b73d3fb40857991a8c6d5d0c7c56b#Lsrc/mat/impls/aij/mpi/mmaij.cT126

Barry touched the code a bit earlier to add this case:

https://bitbucket.org/petsc/petsc-dev/commits/c997baff1558fd165412be034e812bb69f90972a

Prior to that, Mark had reversed the meaning of that bit of code:

https://bitbucket.org/petsc/petsc-dev/commits/a85625d104df12863d7d1735f9fdbe9b281ef7d2#chg-src/mat/impls/aij/mpi/mmaij.c

Even in Barry's original code, I don't understand why we can expect this
check to be producing a collective result. Surely there can be some ranks
that see everything evenly divide and others that do not.

It seems to me that we should either (a) explicitly disallow matrices with
a block size to be built when the blocks are not filled or (b) when the
user requests blocks, pad blocks so that we can always use an ISBlock.


On Mon, Feb 18, 2013 at 2:35 PM, Garth N. Wells <gnw20 at cam.ac.uk> wrote:

> I have some code using ML as a preconditioner, and  it works fines
> with PETSc 3.3 but crashes with PETSc dev. I'm not setting any of the
> ML parameters.  Hopefully someone will recognise the error (below) and
> save me having to bisect the changesets, which is hard because changes
> in PETSc dev make it hard for me to compile against earlier PETSc dev
> revisions.
>
> Garth
>
>
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Petsc has generated inconsistent data!
> [0]PETSC ERROR: Use of blocked not consistant (I am usning blocked)!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Development HG revision:
> 96a09d6a701823d69aede247ed949c1dd4e7c8ff  HG Date: Mon Feb 18 11:08:29
> 2013 -0600
> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [0]PETSC ERROR: See docs/index.html for manual pages.
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Unknown Name on a arch-linux2-c-debug named .......
> Mon Feb 18 19:25:17 2013
> [0]PETSC ERROR: Libraries linked from /home/garth/local/gcc/petsc-dev/lib
> [0]PETSC ERROR:
> [3]PETSC ERROR: See docs/index.html for manual pages.
>
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