[petsc-dev] MatMatMult gives different results

[Hong Zhang]

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/d70cac97/attachment.html>