Opened 4 years ago

Closed 4 years ago

#27493 closed defect (fixed)

Cygwin: OpenBLAS doesn't read environment variables properly

Reported by: embray Owned by:
Priority: critical Milestone: sage-8.8
Component: porting: Cygwin Keywords:
Cc: Merged in:
Authors: Erik Bray Reviewers: Volker Braun
Report Upstream: Fixed upstream, but not in a stable release. Work issues:
Branch: abe0d27 (Commits, GitHub, GitLab) Commit: abe0d276b890bc1005158ad39011443b62d55296
Dependencies: Stopgaps:

Status badges

Description

In Sage we currently, by default, disable multithreading in OpenBLAS by setting OPENBLAS_NUM_THREADS=1 in sage-env.

While this is not ideal, it does reduce the likelihood of multithreading issues coming up in contexts where it wasn't explicitly requested.

While investigating #27434, I found that there is a subtle and apparently rare bug in OpenBLAS's multithreading on Windows, which was causing the docbuild to hang, particularly while building the plot3d docs (which happen to exercise this area of the code more than anything else in Sage).

It occurred to me, however, that the docbuild should not be exhibiting the bug since we set OPENBLAS_NUM_THREADS=1. It turns out this is due to a bug in OpenBLAS on Cygwin, fixed by the attached patch.

I'm setting this to "critical" since it would be very good to have this fixed for the buildbot. I think this bug has been affecting Cygwin for a long time, but I could never nail down why. Nevertheless since we have lived with this bug thus far I won't consider it a blocker.

Upstream PR: https://github.com/xianyi/OpenBLAS/pull/2060

Change History (5)

comment:1 Changed 4 years ago by embray

Branch: u/embray/ticket-27493
Commit: abe0d276b890bc1005158ad39011443b62d55296
Status: newneeds_review

New commits:

abe0d27Trac #27493: Patch OpenBLAS to read environment variables properly on

comment:2 Changed 4 years ago by embray

Report Upstream: N/AFixed upstream, but not in a stable release.

comment:3 Changed 4 years ago by embray

Milestone: sage-8.7sage-8.8

Moving all blocker/critical issues from 8.7 to 8.8.

comment:4 Changed 4 years ago by vbraun

Reviewers: Volker Braun
Status: needs_reviewpositive_review

comment:5 Changed 4 years ago by vbraun

Branch: u/embray/ticket-27493abe0d276b890bc1005158ad39011443b62d55296
Resolution: fixed
Status: positive_reviewclosed
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