Dear Petsc users, I would like to understand what is slowing down the assembly phase of my matrix. I create a matrix with MatCreateMPIAIJ i make a rough guess of the number of off diagonal entries and then use a conservative value to make sure I do not need extra mallocs. (the number of diagonal entries is exact) next i call MatSetValues and MatAssemblyBegin, MatAssemblyEnd. The first time i call MatSetValues and MatAssemblyBegin, MatAssemblyEnd it takes about 170 seconds the second time 0.3 seconds. I run it on 6 cpu's and I do fill quit a number of row-entries on the "wrong" cpu. However thats also the case the second run. I checked that there are no additional mallocs MatGetInfo info.mallocs=0 both after MatSetValues and after MatAssemblyBegin, MatAssemblyEnd.
cheers Thomas
