[petsc-users] ERROR: Scalar value must be same on all processes

[Barry Smith]

> On May 26, 2015, at 2:14 AM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Vijay Gopal Chilkuri <vijay.gopal.c at gmail.com> writes:
>> So somehow the optimization flags effect the code execution !?
>> is this a known issue ?
> 
> Either your code is invalid (e.g., undefined behavior), numerically
> unstable, or your vendor has a bug that you should report.

   So first run with valgrind to find any memory issues http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind

   If/when that is clean slowly start putting back compiler optimization options (first just something like -O2) until you have a problem.

   Barry

Optimization compiler flags are not all that common but do happen, though most of the time it is a user or PETSc bug