From: Mark H Weaver <mhw@netris.org>
To: Nala Ginrut <nalaginrut@gmail.com>
Cc: "Ludovic Courtès" <ludo@gnu.org>,
guile-devel@gnu.org, 13188-done@debbugs.gnu.org
Subject: bug#13188: Whats' the proper senario of par-map? (Was Re: bug#13188: par-map causes VM stack overflow)
Date: Thu, 28 Mar 2013 01:05:32 -0400 [thread overview]
Message-ID: <874nfwazc3.fsf__28631.6204387278$1364447229$gmane$org@tines.lan> (raw)
In-Reply-To: <1364439334.2730.41.camel@Renee-desktop.suse> (Nala Ginrut's message of "Thu, 28 Mar 2013 10:55:34 +0800")
Nala Ginrut <nalaginrut@gmail.com> writes:
> But I'm still puzzled with the performance of par-map:
> --------------------cut-------------------
> scheme@(guile-user)> ,time (define a (map (lambda (x) (expt x 5)) (iota
> 10000)))
> ;; 0.008019s real time, 0.007979s run time. 0.000000s spent in GC.
> scheme@(guile-user)> ,time (define a (par-map (lambda (x) (expt x 5))
> (iota 10000)))
> ;; 6.596471s real time, 6.579375s run time. 1.513880s spent in GC.
> --------------------end-------------------
>
> So my question is, what's the proper scenario to use par-map?
It only makes sense to use 'par-map' when the procedure is fairly
expensive to compute. There is inevitably a lot of overhead in creating
and joining the threads. Granted, we should be able to do much better
than we're doing now, but it would *never* make sense to use 'par-map'
when each computation is as simple as (expt x 5).
Regards,
Mark
next prev parent reply other threads:[~2013-03-28 5:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-15 8:12 bug#13188: par-map causes VM stack overflow Nala Ginrut
2013-03-27 17:12 ` Ludovic Courtès
2013-03-28 2:55 ` bug#13188: Whats' the proper senario of par-map? (Was Re: bug#13188: par-map causes VM stack overflow) Nala Ginrut
[not found] ` <1364439334.2730.41.camel@Renee-desktop.suse>
2013-03-28 5:05 ` Mark H Weaver [this message]
[not found] ` <874nfwazc3.fsf@tines.lan>
2013-03-28 13:44 ` Ludovic Courtès
[not found] ` <87r4izprks.fsf@gnu.org>
2013-03-28 18:00 ` Mark H Weaver
[not found] ` <87ip4b9zfv.fsf@tines.lan>
2013-03-28 20:07 ` Ludovic Courtès
2013-03-29 2:36 ` Nala Ginrut
[not found] ` <1364524610.2730.48.camel@Renee-desktop.suse>
2013-03-29 9:52 ` Ludovic Courtès
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