GNU bug report logs - #14756
threads - par-map - multicore issue

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From: Andy Wingo <wingo <at> pobox.com>
To: ludo <at> gnu.org
Cc: 14756 <at> debbugs.gnu.org, David Pirotte <david <at> altosw.be>
Subject: bug#14756: threads - par-map - multicore issue
Date: Tue, 21 Jun 2016 08:51:09 +0200

I see this, but I'm not quite sure what's going on.  What I do see is
that par-map of 1+ on a list is horribly slow, both on 2.0 and master.
Ludovic do you know what's going on here?

Andy

On Sun 30 Jun 2013 20:00, David Pirotte <david <at> altosw.be> writes:

> Hello,
>
> 	guile --version
> 	guile (GNU Guile) 2.0.9.20-10454
>
> It seems that the par-map not using all cores problem has some how been reintroduced?
>
> 	guile -c '(begin (use-modules (ice-9 threads)) (par-map 1+ (iota 400000)))'
>
> only uses 1 core [it seems it uses some other [maybe all, i can't tell] a couple of
> milliseconds, then drops to 1 core only.
>
> Thanks,
> David
>
> ;; -- 
>
> david <at> idefix:~ 16 $ guile -c '(begin
>>     (use-modules (ice-9 threads))
>>     (par-map 1+ (iota 400))
>>     (display (current-processor-count)) (display "\n")
>>     (display (length (@@ (ice-9 futures) %workers))) (display "\n"))'
> 12
> 11

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