From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Mark H Weaver Newsgroups: gmane.lisp.guile.devel Subject: Extremely high overhead of 'par-map' Date: Fri, 29 Mar 2013 02:00:26 -0400 Message-ID: <878v56agp1.fsf_-_@tines.lan> References: <1355559152.27310.5.camel@Renee-desktop.suse> <87y5d8rclr.fsf@gnu.org> <1364439334.2730.41.camel@Renee-desktop.suse> <874nfwazc3.fsf@tines.lan> <1364524610.2730.48.camel@Renee-desktop.suse> <87d2uiah6h.fsf@tines.lan> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1364536849 27478 80.91.229.3 (29 Mar 2013 06:00:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 29 Mar 2013 06:00:49 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Fri Mar 29 07:01:16 2013 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ULSNC-0003SE-5o for guile-devel@m.gmane.org; Fri, 29 Mar 2013 07:01:10 +0100 Original-Received: from localhost ([::1]:50045 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULSMn-0008BT-Fs for guile-devel@m.gmane.org; Fri, 29 Mar 2013 02:00:45 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:55817) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULSMi-0008Al-U3 for guile-devel@gnu.org; Fri, 29 Mar 2013 02:00:42 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ULSMi-0000gT-3E for guile-devel@gnu.org; Fri, 29 Mar 2013 02:00:40 -0400 Original-Received: from world.peace.net ([96.39.62.75]:53674) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ULSMh-0000gN-WC for guile-devel@gnu.org; Fri, 29 Mar 2013 02:00:40 -0400 Original-Received: from 209-6-91-212.c3-0.smr-ubr1.sbo-smr.ma.cable.rcn.com ([209.6.91.212] helo=tines.lan) by world.peace.net with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.72) (envelope-from ) id 1ULSMb-0000sZ-6N; Fri, 29 Mar 2013 02:00:33 -0400 In-Reply-To: <87d2uiah6h.fsf@tines.lan> (Mark H. Weaver's message of "Fri, 29 Mar 2013 01:49:58 -0400") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 96.39.62.75 X-BeenThere: guile-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:16053 Archived-At: I wrote: > Nala Ginrut writes: >> --------------------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------------------- > [...] >> Well, is there any example? > > The timings above suggest that, on your machine, the overhead of > 'par-map' is in the neighborhood of 660 microseconds per thread (that's > the total run time divided by 10000 iterations). I must say that 'par-map' has shockingly poor performance. We really ought to try to improve this. Mark