From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3676 invoked by alias); 9 May 2012 12:54:15 -0000 Received: (qmail 3667 invoked by uid 22791); 9 May 2012 12:54:14 -0000 X-SWARE-Spam-Status: No, hits=-4.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 09 May 2012 12:54:02 +0000 From: "fh_p at hotmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/53292] multi-threaded (OpenMP) is slower than single-threaded Date: Wed, 09 May 2012 12:56:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: fh_p at hotmail dot com X-Bugzilla-Status: RESOLVED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-05/txt/msg01005.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292 --- Comment #4 from FH 2012-05-09 12:53:46 UTC --- I don't understand your answer. Timing just times the for loop. Checking array content is single threaded : this is added to make sure the for loop has done the job correctly and this check is not timed. The array to initialize is shared by threads (shared by default) ans not private to each thread. To me, the test seems relevant. If it's not, why ? And how to modify it ?