On Mon, Sep 27, 2010 at 18:24, Barry Smith <bsmith at mcs.anl.gov> wrote: > > ?We need an efficient MatAXPY() that works well for any combination of > nonzero patterns. This is not terribly difficult to write. ?Basically for > each row create a linked list of the nonzeros in it from the first matrix and > then merge in the nonzeros from the second matrix for that row, much like in > the LU symbolic factorizations. This will give you row counts, then > preallocate the correct nonzero matrix and do the MatSetValues() for the > first matrix first row then the second matrix first row etc. Finally swap in > the new matrix body into the current matrix.
I don't see why you'd need a linked list for this, you have two sorted arrays (one for each row) and just need to count the number of unique elements. It's one loop. Jed
