[petsc-users] Problem with Optimised version .vs. Debug version

[Jed Brown]

On Wed, Dec 7, 2011 at 06:31, Bogdan Dita <bogdan at lmn.pub.ro> wrote:

> A few weeks ago i posted a question regarding a problem with the
> optimised version of PETSc, what i mean is that I obtained a higher
> solving time with the optimised version then with the debug
> version(~10-15% higher).
>

What do you get from 'mpicc -show'?

MPICH2 has a tendency to put optimization flags into the wrappers. It's
possible that the "optimized" build of PETSc is effectively using -O2 (from
MPICH2) and -g3 (from PETSc with-debugging=1), which might be faster than
-O2 (from MPICH2) -O (from PETSc with-debugging=0, taking precedence) that
you get when you. You can use PETSc's --COPTFLAGS to set your own
optimization flags for PETSc.

Let us know if this works.
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