bug#63986: Julia is very slow

[Efraim Flashner]

On Thu, Jun 22, 2023 at 03:26:30PM +0200, Cayetano Santos wrote:
> 
> 
> >mer. 21 juin 2023 at 22:39, Cayetano Santos <csantosb@inventati.org> wrote:
> 
> >>mer. 21 juin 2023 at 16:36, Ludovic Courtès <ludovic.courtes@inria.fr> 
> >>wrote:
> >
> >> Hey!
> >>
> >> The benchmark you posted, Cayetano, is:
> >>
> >>   julia -e 'using Pkg; Pkg.add("BenchmarkTools"); using BenchmarkTools; N 
> >> = 1000; A = rand(N, N); B = rand(N, N); @btime $A*$B'

I've been having a hard time with that command, so I've been running
julia -e 'using Pkg; Pkg.add("BenchmarkTools"); using BenchmarkTools; N = 1000; 
A = rand(N, N); B = rand(N, N); @time A*B'

I'm not sure if that's useful or not but I didn't see a different with
LIBBLAS* set.

> >>
> >> This is a matrix multiplication that gets delegated to the underlying
> >> BLAS right.  Running it under ‘perf record’ confirms it:
> >>
> >> Samples: 139K of event 'cycles:u', Event count (approx.): 99624880590
> >> Overhead  Command      Shared Object               Symbol
> >>   35.27%  .julia-real  libblas.so.3.9.0            [.] dgemm_
> >>    3.99%  .julia-real  libjulia-internal.so.1.8    [.] gc_mark_loop
> >>    2.60%  .julia-real  libjulia-internal.so.1.8    [.] apply_cl
> >>    1.06%  .julia-real  libjulia-internal.so.1.8    [.] jl_get_binding_
> >>
> >> We’re using libblas.so (presumably from the ‘lapack’ package) and not
> >> OpenBLAS, so no wonder it’s slow.
> >>
> >> Could it be that:
> >>
> >>          "LIBBLAS=-lopenblas"
> >>          "LIBBLASNAME=libopenblas"
> >>
> >> is ineffective?  I think we have a lead!
> >
> > Are we following all instructions here ?
> >
> >   
> > https://docs.julialang.org/en/v1.8/devdocs/build/distributing/#Notes-on-BLAS-and-LAPACK
> >
> > I’m thinking about the variables LIBLAPACK and LIBLAPACKNAME.
> 
> To complete my previous comment, I just realised that
> 
>   Base.USE_BLAS64
> 
> gives "true" when running fast. Guix julia gives "false".
> 
> C.

I'll see what comes with switching it to blas64

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