From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,bf03d731a6ef511f X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!news3.google.com!proxad.net!feeder1-2.proxad.net!news.mixmin.net!aioe.org!not-for-mail From: =?iso-8859-15?Q?Hibou57_=28Yannick_Duch=EAne=29?= Newsgroups: comp.lang.ada Subject: Re: Copying rows in a two dimensional array. Date: Sun, 14 Feb 2010 02:54:37 +0100 Organization: At Home Message-ID: References: <4b6637a1$0$4586$4d3efbfe@news.sover.net> NNTP-Posting-Host: Hf1h0Zy4x3U6eJBIgF+soA.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes Content-Transfer-Encoding: Quoted-Printable X-Complaints-To: abuse@aioe.org X-Notice: Filtered by postfilter v. 0.8.2 User-Agent: Opera Mail/10.10 (Win32) Xref: g2news1.google.com comp.lang.ada:9210 Date: 2010-02-14T02:54:37+01:00 List-Id: Le Sun, 14 Feb 2010 01:42:13 +0100, jonathan a= = =E9crit: > First example: we eigen-decompose an N x N =3D 2048 x 2048 matrix. > The data storage matrix is M x M =3D (1024+Padding) x (1024+Padding) > Here is the running time in seconds of an iterative jacobi > eigen-decomposition: > > 2048x2048: 322 sec, gnat (Padding=3D24) > 2048x2048: 1646 sec, gnat (Padding=3D0) > 2048x2048: 1632 sec, gfortran (Padding=3D0) > 2048x2048: 1492 sec, ifort (Padding=3D0) > > The observed 500% slowdown in the absence of padded arrays is > unacceptable, even if it is a rare event (occurring only on 2**p sized= > data arrays). In fact it's not all that rare ... more comments on > that below. (BTW, ifort is the INTEL fortran compiler, all > optimizations at Max. gfortran is the gcc variant.) So this is mostly about representation clauses finally. Is that it ? Do not know if you already know this document (as I remember I picked it= = up from some one thread at comp.lang.ada), I've talked about on the othe= r = fr.c.l.a : http://research.scee.net/files/presentations/gcapaustralia09/Pitfalls_of= _Object_Oriented_Programming_GCAP_09.pdf I had pointed about frames #17, #18, #19 et #20, which contains good = source of inspiration. Hope this could help you to figure a path. You've posted a long list of tests-bench and observations. I did not = looked at every thing, but hope I will have a more closer look at it lat= er. -- = No-no, this isn't an oops ...or I hope (TM) - Don't blame me... I'm just= = not lucky