Hi Seb,
On 1 May 2020 at 14:18, Sébastien Villemot wrote: | Le vendredi 01 mai 2020 à 07:05 -0500, Dirk Eddelbuettel a écrit : | > On 1 May 2020 at 05:16, Mo Zhou wrote: | > > On Thu, Apr 30, 2020 at 11:26:23PM -0500, Dirk Eddelbuettel wrote: | > > > Switching to libopenblas0-openmp works but one needs to uninstall | > > > libopenblas0-pthread (or else fiddle with the alternatives priority). | > > | > > Does that mean the update-alternatives mechanism is malfunctioning? | > | > I do not know. | > | > It could just be the default ranking is wrong. I did not check, and was | > interested in fiddling manually (as I find it always bites me years later...) | > | > Given that openblas-pthread renders R _unuseable_ and that Seb said it was a | > known issue, maybe we should ensure it ranks lower than it currently does? | | I did not say that it is a known issue. I said that we had a similar | issue in the past, but that it was solved. | | Also, I tried to reproduce the problem on an unstable system with | OpenBLAS/pthreads selected as the alternative, but I couldn’t. The | computation goes fine for me. So I guess the problem manifests only on | specific systems or CPUs. | | I suggest that you open a bug report, providing as many details as | possible on the system where it manifests (in particular, the precise | CPU model). | | Also, I don’t think we should change the alternatives priorities. The | OpenMP flavour of OpenBLAS has its own problems (in particular, because | it is compiled with GNU OpenMP, it is incompatible with applications | compiled against Intel’s OpenMP, and we cannot do anything about that). | So we should rather fix the bug that you encountered. For what it is worth, on my (personal) workstation I re-encountered the bug yesterday, chiefly because "it is still there" and the default ordering does not help me -- quite the contrary, it "causes it". All I did was to go from Ubuntu 19.10 to 20.04; I have a i7-8700k cpu and the simple test of `example(solve)` reliably hangs R. Rememy: sudo apt install libopenblas-openmp-dev sudo apt remove libopenblas0-pthread After that things are fine again. It's a tricky issue for newb. It would be really good if we could squash / circumvent it. I would be happy to test newer/different version if you have them. I could drop any new Debian sources onto my PPA to test them on this box. Dirk -- http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org