[petsc-dev] MatMatMult gives different results

[Hong Zhang]

Alexander,
I'm curious about why do you need parallel C=A^T*B?
How large your matrices are?

In petsc-dev, we have MatTransposeMatMult() for mpiaij and mpiaij, but not
mpiaij and mpidense.
We may add support of MatTransposeMatMult_MPIAIJ_MPIDense() if there is
such need.

Hong


On Tue, Feb 7, 2012 at 1:18 PM, agrayver at gfz-potsdam.de <
agrayver at gfz-potsdam.de> wrote:

> Hong,
>
> Thanks for explanation. I will try this tomorrow. Good to have this stuff
> in the help now.
>
> And sorry for misleading you initially.
>
> Regards,
> Alexander
>
>
> ----- Reply message -----
> From: "Hong Zhang" <hzhang at mcs.anl.gov>
> To: "For users of the development version of PETSc" <petsc-dev at mcs.anl.gov
> >
> Subject: [petsc-dev] MatMatMult gives different results
> Date: Tue, Feb 7, 2012 19:09
>
>
> Alexander :
>
>>
>> There is something I didn't get yet, I hope you could clarify it.
>>
>> So, when I use flag MAT_INITIAL_MATRIX in test program it works fine.
>>
> Good to know :-)
>
>
>> If I put this flag in my original program I get dozens of exceptions like:
>> [42]PETSC ERROR: Argument out of range!
>> [42]PETSC ERROR: New nonzero at (1336,153341) caused a malloc!
>>
> You cannot do
>  MatCreateMPIAIJ()
> MatTranspose(A,MAT_INITIAL_MATRIX,&AT);
>
> MatCreateMPIAIJ() creates AT and preallocates approximate nonzeros, which
> does not match exactly the nonzeros in
> MatTranspose(A,MAT_INITIAL_MATRIX,&AT);
> MatTranspose(A,MAT_INITIAL_MATRIX,&AT) creates matrix AT and sets correct
> nonzero pattern and values in AT.
> MatTranspose() only takes in "MAT_INITIAL_MATRIX" - for a new AT,
> and "MAT_REUSE_MATRIX" when AT is created with
> MatTranspose(A,MAT_INITIAL_MATRIX,&AT)
> and reuse for updating its values (not nonzero patten).
>
> I'm updating petsc help menu on MatTranspose(). Thanks for the report.
>
> Hong
>
>
>> I changed this flag to MAT_REUSE_MATRIX and exceptions disappeared, but
>> result is incorrect again (same as for MAT_IGNORE_MATRIX)
>> I tried test program with MAT_REUSE_MATRIX and it also gives different
>> matrix product.
>>
>> Since there is no description of MatReuse structure for MatTranspose it's
>> a bit confusing what to expect from it.
>>
>>
>>>  Do you mean 'Cm = A'*B;'?
>>> 'Cm = A.'*B;' gives component-wise matrix product, not matrix product.
>>>
>>>
>>>  .' operator means non-Hermitian transpose. That is what I get with
>>> MatTranspose (in contrast with MatHermitianTranspose)
>>> component-wise matrix product would be .*
>>>
>> You are correct.
>>
>>  Hong
>>
>>>
>>>
>>>
>>>  Hong
>>>
>>>
>>>
>>>>  C = PetscBinaryRead('C.dat','complex',true);
>>>>
>>>> Matrix C is different depending on number of cores I use.
>>>> My PETSc is:
>>>> Using Petsc Development HG revision:
>>>> 876c894d95f4fa6561d0a91310ca914592527960  HG Date: Tue Jan 10 19:27:14 2012
>>>> +0100
>>>>
>>>>
>>>> On 06.02.2012 17:13, Hong Zhang wrote:
>>>>
>>>> MatMatMult() in petsc is not well-tested for complex - could be buggy.
>>>> Can you send us the matrices A and B in petsc binary format for
>>>> investigation?
>>>>
>>>>  Hong
>>>>
>>>> On Mon, Feb 6, 2012 at 5:55 AM, Alexander Grayver <
>>>> agrayver at gfz-potsdam.de> wrote:
>>>>
>>>>> Dear PETSc team,
>>>>>
>>>>> I try to use:
>>>>> call
>>>>> MatMatMult(A,B,MAT_INITIAL_MATRIX,PETSC_DEFAULT_DOUBLE_PRECISION,C,ierr);CHKERRQ(ierr)
>>>>>
>>>>> Where both A and B are rectangular, but A is sparse and B is dense.
>>>>> Both are double complex and distributed.
>>>>> The product PETSc gives me contains some errors in some part of the
>>>>> matrix.
>>>>> I output A, B and C then computed product in matlab.
>>>>>
>>>>> Attached you see figure plotted as:
>>>>> imagesc(log10(abs(C-Cm)))
>>>>>
>>>>> Where Cm -- product computed in matlab.
>>>>>
>>>>> The pattern and amplitude vary depending on the number of cores I use.
>>>>> This picture is obtained for 48 cores (I've tried 12, 64 cores as well).
>>>>>
>>>>> Where should I look for possible explanation?
>>>>>
>>>>> --
>>>>> Regards,
>>>>> Alexander
>>>>>
>>>>
>>>>
>>>>
>>>>   --
>>>> Regards,
>>>> Alexander
>>>>
>>>>
>>>
>>>
>>>   --
>>> Regards,
>>> Alexander
>>>
>>>
>>
>>
>> --
>> Regards,
>> Alexander
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120207/628fad73/attachment.html>