bug#63986: Julia is very slow

[Efraim Flashner]

On Fri, Sep 29, 2023 at 10:46:07AM +0200, Ludovic Courtès wrote:
> Hi,
> 
> Efraim Flashner <efraim@flashner.co.il> skribis:
> 
> > On Mon, Sep 25, 2023 at 04:46:57PM +0200, Ludovic Courtès wrote:
> 
> [...]
> 
> >> >   
> >> > /gnu/store/h5mgc7ar7a05f9rwrd1makhzays5wd3s-julia-1.8.3/bin/../lib/julia/liblapack.so:
> >> >  undefined symbol: dsfrk_64_
> >> 
> >> The ‘_64’ suffix is added by a patch in this very series, that adds
> >> ‘SYMBOLSUFFIX=64_’ to ‘openblas-ilp64’.
> >> 
> >> I don’t know what the rationale was for that configuration change, but
> >> this is a good area of investigation.
> >> 
> >> Efraim, WDYT?
> >
> > the SYMBOLSUFFIX change seems to be standard across other distributions,
> > and in fact there seem to be packages out there which rely on it
> > directly.
> >
> > Looking at this error specifically and also the pcre2-8 errors we get
> > during the 'test phase for julia, it seems the suggested fix is to build
> > those libraries with julia. So we'd want to replace the pcre2 and the
> > lapack libraries in the julia sources (for pcre2 for all the
> > architectures, for lapack for x86_64 specifically) and let julia build
> > and link to them during the build phase.
> 
> That would seem like a step backwards though, no?  Usually we prefer to
> unbundle things.

I tried it with inserting our source for pcre2 and adding a patch to fix
the configure phase of pcre2, we ended up with other failures, so I
think we're best off with what we have now.

> Actually, why does liblapack.so end up in Julia itself, as opposed to
> just linking to libopenblas.so?

Julia links to both (open)blas and to lapack. If we build openblas so
that it also provides lapack, or use (c)blas from lapack, then we can
use only one or the other. I suppose in theory it should be possible to
tell julia that libopenblas64_.so is really lapack and to use that for
both of them. I don't know how well that would work though.

-- 
Efraim Flashner   <efraim@flashner.co.il>   רנשלפ םירפא
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