using GAP fails when julia is using multiple threads
#960
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I cannot reproduce this problem under Ubuntu 20.04 with Julia 1.8.5 and 1.9.0, with various values for the |
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I have it working perfectly fine with 1.9.3, it seems to be an issue only with julia 1.10
… On Jan 19, 2024, at 12:59 PM, Thomas Breuer ***@***.***> wrote:
I cannot reproduce this problem under Ubuntu 20.04 with Julia 1.8.5 and 1.9.0, with various values for the -t command line option. Would it make sense to try other Julia versions with this setup?
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A workaround to load GAP in a julia session with threads enabled is to disable gcthreads with The following seems to work fine with julia 1.10: Tests also work in this configuration: |
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Thanks for writing up a report, @mjrodgers I can reproduce it with Julia 1.10.0 on macOS. I will look into this, but possibly only after February 1st, due to the book |
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There are multiple issues here in the GAP-Julia GC integration. One is the now incorrect usage of the variable Then there is the use of a bunch of global variables in there (in GAP's
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Just hit the same bug when installing Oscar and got a segmentation fault. |
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I made some progress on this today: turns out I have to change function I also added a mutex to protect access to Alas, there are still issues. So the next thing I did was to add a global GAP list and then any allocation is added to that list, and any GC marks that list -- this should prevent any GAP allocation from ever be garbage collected. (Clearly this is not useful for a production system, but it helps to exclude certain issues). But despite this, I am still seeing errors that are highly suggestive of GAP objects being GCed prematurely. Hrm. |
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This should be fixed in GAP.jl 0.11.2 and later. |
Edit (@thoma): As a workaround, start julia with
--gcthreads=1.When starting julia using multiple threads (
julia -t 4),using GAPcan fail. This also seems to leave julia in a fragile state, and I get a segfault when quitting.Interestingly,
using GAPseems to work fine if I launch julia using 3 threads, but 4 is a problem.I'm running on an Intel Mac running Sonoma 14.2.1, julia 1.10.0, GAP 0.10.1
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