On Thu, 31 Dec 2015, oleg_komashko@ukr.net wrote:

> Thank you, Marcin It helped. Interesting, it's a new version of 
> libblas or gretl? The same configure settings worked clean for 
> more than a year

That's because we were ignoring the potential problem of OpenBLAS 
running pthreads under OpenMP. Now we're not ignoring it any more.

As Jack has said, we don't have firm evidence that this is a 
practical problem. If it were, the most likely symptom would be a 
hang in OpenBLAS. At one point lately we were worried that mixing 
the two methods was leading to a crash, but that turned out not to 
be the case -- the crash had a different cause, namely an unrelated 
bug in OpenBLAS, against which gretl now has a work-around. See

https://github.com/xianyi/OpenBLAS/issues/723

The basic point, however, is that the interaction of OpenMP and 
pthreads is undefined.

The OpenBLAS library can be built to use OpenMP instead of pthreads, 
via the flag "USE_OPENMP = 1" in Makefile.rule. Some Linux distros 
(e.g. Fedora) offer pre-built OpenBLAS in both "flavours": pthreads 
or OpenMP.

Allin
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