[petsc-dev] Broken MatMatMult_MPIAIJ_MPIDense

[Zhang, Hong]

Yes, we should allow users to provide their own matrix array.

We use MatDensePlaceArray() to plug an array into matrix C before MatMatMult(). If we cannot do this, we will have to copy from the internal array of the result C to our array.

Would the following sequence work?
MatMatMultSymbolic()
MatDensePlaceArray()
MatMatMultNumeric()
This seems a reasonable API, but it is not obvious to users when and where MatDensePlaceArray() should be called.
Currently, most users call  MatMatMult(A,B, reuse,&C) instead of MatMatMultSymbolic/Numeric.

We plan to add
MatMatGetProduct(A,B,&C);
Then,
MatDensePlaceArray(C,array);

Hong
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