Something weird with SNES convergence reason

Rafael Santos Coelho rafaelsantoscoelho at
Wed May 14 22:30:01 CDT 2008

Hello everybody,

I've coded a program which solves, in parallel, the three-dimensional Bratu
problem. Afterwards, I've run tests in a cluster to see how it would go and,
at first, it seemed ok to me, but then I've noticed that whenever I
increased the number of processors (from 16 to 32, for example), the program
started to diverge due to a failure in the Line Search Newton's Method. Here
is what a monitoring function prints out:

nonlinear iteration number  = 1, norm(F(x)) = 1013.53, linear iterations =
nonlinear iteration number  = 2, norm(F(x)) = 1013.33, linear iterations =
nonlinear iteration number  = 3, norm(F(x)) = 1013.33, linear iterations =
Nonlinear solve did not converge due to DIVERGED_LS_FAILURE

Indeed, one can see that the method is really diverging (for smaller tests,
though, say N = 8 * 8 * 8, it converges).

What's wrong here? Is it something with my code? If yes, how can I fix it?

Best regards,

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