[petsc-users] Valgrind Errors

[Hong]

James,
The fix is pushed to petsc-maint (release)
https://bitbucket.org/petsc/petsc/commits/c974faeda5a26542265b90934a889773ab380866

Thanks for your report!

Hong

On Mon, Sep 15, 2014 at 5:05 PM, Hong <hzhang at mcs.anl.gov> wrote:
> James :
> I'm fixing it in branch
> hzhang/matmatmult-bugfix
> https://bitbucket.org/petsc/petsc/commits/a7c7454dd425191f4a23aa5860b8c6bac03cfd7b
>
> Once it is further cleaned, and other routines are checked, I will
> patch petsc-release.
>
> Hong
>
>> Hi Barry,
>>
>> Thanks for the response.  You're right, it (both ex70 and my own code) doesn't give those valgrind errors when I run it in parallel.  Changing the type to MATAIJ also fixes the issue.
>>
>> Thanks for the help, I appreciate it.
>>
>>     James
>>
>>
>>
>>
>>
>>> -----Original Message-----
>>> From: Hong [mailto:hzhang at mcs.anl.gov]
>>> Sent: Friday, September 12, 2014 4:29 PM
>>> To: Dominic Meiser
>>> Cc: Barry Smith; James Balasalle; Zhang, Hong; petsc-users at mcs.anl.gov
>>> Subject: Re: [petsc-users] Valgrind Errors
>>>
>>> I'll check it.
>>> Hong
>>>
>>> On Fri, Sep 12, 2014 at 3:40 PM, Dominic Meiser <dmeiser at txcorp.com>
>>> wrote:
>>> > On 09/12/2014 02:11 PM, Barry Smith wrote:
>>> >>
>>> >>     James (and Hong),
>>> >>
>>> >>      Do you ever see this problem in parallel runs?
>>> >>
>>> >>      You are not doing anything wrong.
>>> >>
>>> >>      Here is what is happening.
>>> >>
>>> >> MatGetBrowsOfAoCols_MPIAIJ() which is used by
>>> >> MatMatMult_MPIAIJ_MPIAIJ() assumes that the VecScatters for the
>>> >> matrix-vector products are
>>> >>
>>> >>    gen_to   = (VecScatter_MPI_General*)ctx->todata;
>>> >>    gen_from = (VecScatter_MPI_General*)ctx->from data;
>>> >>
>>> >> but when run on one process the scatters are not of that form; hence
>>> >> the code accesses values in what it thinks is one struct but is
>>> >> actually a different one. Hence the valgrind errors.
>>> >>
>>> >> But since the matrix only lives on one process there is actually
>>> >> nothing to move between processors hence no error happens in the
>>> >> computation. You can avoid the issue completely by using MATAIJ
>>> >> matrix for the type instead of MATMPIAIJ and then on one process it
>>> automatically uses MATSEQAIJ.
>>> >>
>>> >> I don’t think the bug has anything in particular to do with the
>>> >> MatTranspose.
>>> >>
>>> >>    Hong,
>>> >>
>>> >>      Can you please fix this code? Essentially you can by pass parts
>>> >> of the code when the Mat is on only one process. (Maybe this also
>>> >> happens for MPIBAIJ matrices?) Send a response letting me know you
>>> saw this.
>>> >>
>>> >>     Thanks
>>> >>
>>> >>       Barry
>>> >
>>> > I had to fix a few issues similar to this a while back. The method
>>> > VecScatterGetTypes_Private introduced in pull request 176 might be
>>> > useful in this context.
>>> >
>>> > Cheers,
>>> > Dominic
>>> >
>>
>>
>>
>>
>>
>>
>>
>>
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