[Trilinos-Users] Performance Question about Epetra_FECrsMatrix (and probably Tpetra::CrsMatrix too)

[Pat Notz]

I'm doing typical FEM assemblies using an Epetra_FECrsMatrix and it
appears to be working correctly. However, I've been profiling the
serial performance and I have some concerns.

In general, we're making off-processor contributions so we have to use
global row/col ids. The SumIntoGlobalValues method does some
gymnastics to see if the contributions are local or global and that
results in a lot of calls to LID(gid) -- it's LID() that's showing up
high in my profile.

As far as I can tell, it appears that you can use local ids for
locally *owned* contributions but there's no notion of an equally
cheap local id for shared-but-not-owned contributions. Is that right?

I'm open to switching to Tpetra if things are better there (I may be
switching anyway).

~ Pat