[petsc-users] The multiplication of the transpose of a dense matrix(A^T) and a large sparse matrix(X1)

[Jed Brown]

Hong Zhang <hzhang at mcs.anl.gov> writes:

> He needs MatTransposeMatMult_MPIDense_MPIAIJ
> This requires huge amount of data communications among MPI processes.

In the original form, the result would have ten rows and 1400 Trillion
columns, which isn't something reasonably storable in a MPIAIJ matrix.
So the column space needs to be compressed, but then it still makes more
sense to store the result matrix in transposed form (as ten columns)
since those can be reasonably distributed.  My MAIJ suggestion would
work that way, as would MatTransposeMatMult_MPIAIJ_MPIDense.