[petsc-dev] Fwd: Suggestions for MatProductCreate()

[hong at aspiritech.org]

Lisandro,

> As I said in previous emails, I'm not complaining about the API, I said it
> was a welcome adition. All I'm asking is:
>
> 1)  Fix the handling of reference counting. This is an implementation
> detail, not really an API change.
>
I'm creating a branch from master and patch it with your suggestions on
reference counting.

>
> 2) Add a simple new routine to the API, MatProductReset(D)  [or maybe name
> it MatProductClear(D) ], that should throw away all of the D->product stuff
> to release memory related to the product algorithm implementation. After
> calling MatProductReset(D), you cannot call anymore MatProductNumeric().
>
Do you mean adding a public function MatProductClear(D) to clear internal
data structure 'product' attached to D?
For example, after destroy A and B, user should call  MatProductClear(D),
i.e.,
MatDestroy(&A) ;
MatDestroy(&B) ;
MatProductClear(D); // throw away all of the D->product stuff, thus D
becomes a standard matrix

I understand that you are concerned about the dangling pointers. However,
most users compute D =A*B, then destroy A, B and D separately in random
order. Do we require user to call MatProductClear(D) after A or B is
destroyed?

>
>> 3) For MatProduct, I consider
>> MatProductSetFromOptions() is logically equivalent to
>> MatSetFromOptions(),
>> MatProductSymbolic() is logically equivalent to MatSetUp(),
>> and
>> MatProductNumeric() assembles the matproduct  D repeatedly when A or B
>> are updated.
>>
>>
> OK, so... your point it that what looks like "setup" code
> in MatProductSetFromOptions() is just some minimal stuff required to
> actually dispatch the SetFromOptions_typeA_typeB routine, right? In that
> case, you are right, no changes/refactors needed here.
>
Yes,  MatProductSetFromOptions() only
dispatches SetFromOptions_typeA_typeB_producttype() which handles local
options and polymorphism. The organization of new API is described at the
top of petsc/src/mat/interface/matproduct.c.

Hong
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