Send the runable case so that we can determine the cause of the slow down and find possible cures. It could be that the "optimized" version was optimized for a particular size of problems or matrix structure. Barry

On Sep 20, 2017, at 4:32 PM, Jed Brown <[email protected]> wrote:

I have a simple SeqAIJ example where MatTransposeMatMult is 30x slower than MatTranspose followed by MatMatMult. This is embarrassing when people try to compare performance. Are there any cases where these custom implementations provide value rather than just confusing people or turning them away from PETSc?