[aspect-devel] PETSc support

[Timo Heister]

> Figured that I should give this a shot, since I was the one interested in
> PETSc/Trilinos comparisons.  I am using petsc 3.4.2 optimized and Trilinos
> 11.2.3.  For the most part here I am following suit by testing with
> composition-passive.prm.

Thanks for looking into this!

> 1) I don't see any assertions being hit in debug mode (but see later).

good.

> 2) Visually, the results seem to be pretty much the same for what I have
> looked at.  I am, however, seeing surpisingly large differences in iteration
> counts.  Specifically, for the temperature/composition solves with PETSc,
> iteration counts are 30-50, as compared to 10-15 for Trilinos.

This might be related to different handling of residuals (do we use
Trilinos, PETSc, or deal.II inner solvers?) but most likely this is
just an artifact of different preconditioners (Hyper vs ML). They were
similar for me in the past, but only for scalar Poisson type problems.

> 3) The overall speed of the two versions is not wildly different for what I
> have looked at.  Certainly nothing like 50x difference.  Perhaps it comes
> down to optimized vs debug PETSc?

This is aspect running in debug or optimized mode? My 50x was optimized.

> Okay, I have run into a big problem, though.  Something is up with running
> on several processors with PETSc in optimized mode.  Basically, aspect never
> gets started.  It looks like not all the processors are returning from the
> MPI initialization step, but I'm still trying to track it down.  It runs
> fine in debug mode, or with one process in optimized mode.

PETSc optimized or Aspect optimized?

Do you get any output if you do
mpirun -n 2 ./aspect -log_summary
or "-log_trace out" and look at the out.* files?


-- 
Timo Heister
http://www.math.clemson.edu/~heister/