Division by zero in interval.cpp about cosma

[kabicm]

We will publish soon (probably tomorrow) the version 2.1, which will include one more feature and will have this bug fixed, so that we can also update it in cp2k :)

[kabicm]

@oschuett Thanks for the issue! Is COSMA here built with MKL? Because I see OMP_NUM_THREADS explicitly set but MKL_NUM_THREADS not.

[oschuett]

It's build with the default toolchain. So, Openblas and Scalapack. We never set MKL_NUM_THREADS in our tests. The div-by-zero occurred in H2O-32.inp with a single MPI rank and 8 OpenMP threads.

[kabicm]

Thanks, I am able to reproduce it. It doesn't seem like a serious bug, just the wrong division strategy is being produced. I will work on it.

[oschuett]

I think, it's best to avoid divisions by zero as they gives undefined results.
In CP2K we often use foo / MAX(1,bar) for these edge cases.

Btw, personally I'm a big fan of floating point exception (which trigger for integers too). They can be very useful while adding virtually no overhead.

[kabicm]

Fixed in commit: 808abd7! Not sure if that would just hide these bugs even more?

[oschuett]

Thanks! Of course, catching these edge cases in a single place, as you did, is the best solution :-)