[petsc-dev] MATOP_MAT_MULT

Jose E. Roman jroman at dsic.upv.es
Thu Apr 23 02:36:09 CDT 2020 

I agree with Pierre. However, if the fix involves an API change then I could understand it goes to master.


> El 23 abr 2020, a las 7:43, Pierre Jolivet <pierre.jolivet at enseeiht.fr> escribió:
> 
> I don’t know if you really meant to ask for José's opinion here, but I personally think that releasing all 3.13.X version with a broken MatMatMult and no deprecation warning concerning MATOP_MAT_MULT is not the best.
> Thanks,
> Pierre
> 
>> On 23 Apr 2020, at 4:03 AM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
>> 
>> Jose,
>> I'll check and fix them. I have to do it in master, is ok?
>> Hong
>> 
>> From: Pierre Jolivet <pierre.jolivet at enseeiht.fr>
>> Sent: Wednesday, April 22, 2020 3:08 PM
>> To: Zhang, Hong <hzhang at mcs.anl.gov>
>> Cc: Jose E. Roman <jroman at dsic.upv.es>; Stefano Zampini <stefano.zampini at gmail.com>; petsc-dev <petsc-dev at mcs.anl.gov>; Smith, Barry F. <bsmith at mcs.anl.gov>
>> Subject: Re: [petsc-dev] MATOP_MAT_MULT
>>  
>> Hong,
>> I also now just tested some previously PETSC_VERSION_LT(3,13,0) running code with C=A*B, Dense=Nest*Dense, all previously allocated prior to a call to MatMatMult and scall = MAT_REUSE_MATRIX.
>> Sadly, it’s now broken. It is my fault for not having a test for this in https://gitlab.com/petsc/petsc/-/merge_requests/2069, sorry about that.
>> [0]PETSC ERROR: Call MatProductSymbolic() first
>> [0]PETSC ERROR: #1 MatProductNumeric() line 730 in /ccc/work/cont003/rndm/rndm/petsc/src/mat/interface/matproduct.c
>> [0]PETSC ERROR: #2 MatMatMult() line 9335 in /ccc/work/cont003/rndm/rndm/petsc/src/mat/interface/matrix.c
>> 
>> Here is a reproducer (that will work OK with 3.12.4).
>> diff --git a/src/mat/tests/ex195.c b/src/mat/tests/ex195.c
>> index c72662bc3c..811de669c5 100644
>> --- a/src/mat/tests/ex195.c
>> +++ b/src/mat/tests/ex195.c
>> @@ -73,2 +73,3 @@ int main(int argc,char **args)
>>    ierr = MatMatMult(nest,B,MAT_REUSE_MATRIX,PETSC_DEFAULT,&C);CHKERRQ(ierr);
>> +  ierr = MatMatMult(nest,C,MAT_REUSE_MATRIX,PETSC_DEFAULT,&B);CHKERRQ(ierr);
>>    ierr = MatMatMultEqual(nest,B,C,10,&equal);CHKERRQ(ierr);
>> 
>> $ make -f gmakefile test searchin=mat_tests-ex195
>> 
>> I believe this is very close to the topic at hand and issue #608, so maybe you could fix this as well in the same upcoming MR? Just let me know, I can have a crack it otherwise.
>> Thanks,
>> Pierre
>> 
>>> On 22 Apr 2020, at 5:38 PM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
>>> 
>>> Jose, Pierre and Stefano,
>>> Now I understand the issue that Stefano raised. I plan to add
>>> MatProductIsSupported(Wmat,&supported,&matproductsetfromoptions)
>>> the flag 'supported' tells if the product is supported/implemented or not,
>>> and the function pointer 'matproductsetfromoptions' gives the name of MatProductSetFromOptions_xxx, (including basic implementation) or NULL.
>>> 
>>> Let me know your suggestions. I'll list all of you as reviewer.
>>> Hong
>>> 
>>>   
>>> From: Jose E. Roman <jroman at dsic.upv.es>
>>> Sent: Wednesday, April 22, 2020 9:07 AM
>>> To: Stefano Zampini <stefano.zampini at gmail.com>
>>> Cc: Zhang, Hong <hzhang at mcs.anl.gov>; Pierre Jolivet <pierre.jolivet at enseeiht.fr>; petsc-dev <petsc-dev at mcs.anl.gov>
>>> Subject: Re: [petsc-dev] MATOP_MAT_MULT
>>>  
>>> I agree with Pierre and Stefano.
>>> Hong: your proposed solution would be fine, but MATOP_MATPRODUCT does not exist yet, so I cannot try it.
>>> I would like a solution along the lines of what Stefano suggests. It is not too much trouble if it goes to master instead of maint.
>>> 
>>> Thanks.
>>> Jose
>>> 
>>> 
>>> > El 22 abr 2020, a las 15:26, Stefano Zampini <stefano.zampini at gmail.com> escribió:
>>> > 
>>> > 
>>> >> 
>>> >> MatProductCreateWithMat(A,Vmat,NULL,Wmat);
>>> >> MatProductSetType(Wmat,MATPRODUCT_AB);
>>> >> MatHasOperation(Wmat,MATOP_MATPRODUCT,&flg); //new support, it calls MatProductSetFromOptions(Wmat)
>>> > 
>>> > Hong, this would go in the direction I was outlining here https://gitlab.com/petsc/petsc/-/issues/608
>>> > How about also adding something like
>>> > 
>>> > MatProductIsImplemented(Wmat,&flg)
>>> > 
>>> > That returns true if a specific implementation is available? This way
>>> > 
>>> > This way, if we use both queries, we can assess the presence of the basic fallbacks too, i.e.
>>> >  
>>> > MatHasOperation(Wmat,MATOP_MATPRODUCT,&flg1)
>>> > MatProductIsImplemented(Wmat,&flg2)
>>> > 
>>> > If flg1 is false, no support at all
>>> > If flg1 is true and flg2 is false -> Basic implementation (i.e, MatShell with products inside)
>>> > If flg1 and flg2 are both true -> Specific implementation available.
>>> > 
>>> >> if (V->vmm && flg) {
>>> >>   MatProductSymbolic(Wmat);
>>> >>   MatProductNumeric(Wmat);
>>> >> } else {
>>> >>   MatDestroy(Wmat);
>>> >>   ...
>>> >> }
>>> >> Hong
>>> >> 
>>> >> 
>>> >> From: Jose E. Roman <jroman at dsic.upv.es>
>>> >> Sent: Tuesday, April 21, 2020 11:21 AM
>>> >> To: Pierre Jolivet <pierre.jolivet at enseeiht.fr>
>>> >> Cc: Zhang, Hong <hzhang at mcs.anl.gov>; petsc-dev <petsc-dev at mcs.anl.gov>
>>> >> Subject: Re: [petsc-dev] MATOP_MAT_MULT
>>> >>  
>>> >> 
>>> >> 
>>> >> > El 21 abr 2020, a las 17:53, Pierre Jolivet <pierre.jolivet at enseeiht.fr> escribió:
>>> >> > 
>>> >> > 
>>> >> > 
>>> >> >> On 21 Apr 2020, at 5:22 PM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
>>> >> >> 
>>> >> >> Pierre,
>>> >> >> MatMatMult_xxx() is removed from MatOps table.
>>> >> > 
>>> >> > Shouldn’t there be a deprecation notice somewhere?
>>> >> > There is nothing about MATOP_MAT_MULT in the 3.13 changelog https://www.mcs.anl.gov/petsc/documentation/changes/313.html
>>> >> > For example, I see that in SLEPc, José is currently making these checks, which are in practice useless as they always return PETSC_FALSE?https://gitlab.com/slepc/slepc/-/blob/master/src/sys/classes/bv/impls/contiguous/contig.c#L191
>>> >> > (Maybe José is aware of this and this is just for testing)
>>> >> 
>>> >> No, I was not aware of this. Thanks for bringing this up. Now in 3.13 we are always doing the slow version (column by column), so yes I am interested in a solution for this.
>>> >> 
>>> >> > 
>>> >> >> MatMatMult() is replaced by
>>> >> >> MatProductCreate()
>>> >> >> MatProductSetType(,MATPRODUCT_AB)
>>> >> >> MatProductSetFromOptions()
>>> >> >> MatProductSymbolic()
>>> >> >> MatProductNumeric()
>>> >> >> 
>>> >> >> Where/when do you need query a single matrix for its product operation?
>>> >> > 
>>> >> > I didn’t want to bother at first with the new API, because I’m only interested in C = A*B with C and B being dense.
>>> >> > Of course, I can update my code, but if I understand Stefano’s issue correctly, and let’s say my A is of type SBAIJ, for which there is no MatMatMult, the code will now error out in the MatProduct?
>>> >> > There is no fallback mechanism? Meaning I could in fact _not_ use the new API and will just have to loop on all columns of B, even for AIJ matrices.
>>> >> > 
>>> >> > Thanks,
>>> >> > Pierre
>>> >> > 
>>> >> >> Hong
>>> >> >> 
>>> >> >> From: petsc-dev <petsc-dev-bounces at mcs.anl.gov> on behalf of Pierre Jolivet <pierre.jolivet at enseeiht.fr>
>>> >> >> Sent: Tuesday, April 21, 2020 7:50 AM
>>> >> >> To: petsc-dev <petsc-dev at mcs.anl.gov>
>>> >> >> Subject: [petsc-dev] MATOP_MAT_MULT
>>> >> >>  
>>> >> >> Hello,
>>> >> >> Am I seeing this correctly?
>>> >> >> #include <petsc.h>
>>> >> >> 
>>> >> >> int main(int argc,char **args)
>>> >> >> {
>>> >> >>   Mat               A;
>>> >> >>   PetscBool         hasMatMult;
>>> >> >>   PetscErrorCode    ierr;
>>> >> >> 
>>> >> >>   ierr = PetscInitialize(&argc,&args,NULL,NULL);if (ierr) return ierr;
>>> >> >>   ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
>>> >> >>   ierr = MatSetType(A,MATMPIAIJ);CHKERRQ(ierr);
>>> >> >>   ierr = MatHasOperation(A,MATOP_MAT_MULT,&hasMatMult);CHKERRQ(ierr);
>>> >> >>   printf("%s\n", PetscBools[hasMatMult]);
>>> >> >>   ierr = PetscFinalize();
>>> >> >>   return ierr;
>>> >> >> }
>>> >> >> 
>>> >> >> => FALSE
>>> >> >> 
>>> >> >> I believe this is a regression (or at least an undocumented change) introduced here:https://gitlab.com/petsc/petsc/-/merge_requests/2524/
>>> >> >> I also believe Stefano raised a similar point there: https://gitlab.com/petsc/petsc/-/issues/608
>>> >> >> This is a performance killer in my case because I was previously using this check to know whether I could use MatMatMult or had to loop on all columns and call MatMult on all of them.
>>> >> >> There is also a bunch of (previously functioning but now) broken code, e.g.,https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/transpose/transm.c.html#line105or https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/nest/matnest.c.html#line2105
>>> >> >> Is this being addressed/documented?
>>> >> >> 
>>> >> >> Thanks,
>>> >> >> Pierre
>>> >> > 
>>> >
>

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