Re: [Gretl-users] OpenBLAS warning
On Thu, 31 Dec 2015, oleg_komashko(a)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