On Feb 1, 2012, at 5:02 AM, Hui Zhang wrote: > > On Jan 31, 2012, at 1:23 PM, Jed Brown wrote: > >> On Tue, Jan 31, 2012 at 04:11, Hui Zhang <mike.hui.zhang at hotmail.com> >> wrote: >> Suppose using MatCreate() and MatSetSizes() we obtain a Mat A, and then >> tion and then using local indices (e.g. MatSetValuesLocal()) during >> assembly. You might use AO for that setup step, but it usually doesn't make >> sense to use _during_ assembly. > > thanks, do you mean that it is faster to use LocaltoGlobalMapping & > SetValuesLocal > than to use AO & SetValues globally? Is there a big difference in performance?
Yes, using the SetValuesLocal approach will be much faster for large problems than using the AO to map to global indices and calling SetValues. Barry > > >> >> with >> P_1 the permutation corresponding to ao_1. In a similar way, we have that b >> becomes P_2 b under the petsc ordering. I want to make sure P_1 and P_2 are >> the same so arises my question. >> >> Thanks a lot! >> Hui >> >> >> >
