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=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,99210dd26e04d959 X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news4.google.com!feeder.news-service.com!feeder1.cambriumusenet.nl!feed.tweaknews.nl!194.134.4.91.MISMATCH!news2.euro.net!newsfeed.freenet.ag!news.netcologne.de!ramfeed1.netcologne.de!newsfeed.arcor.de!newsspool2.arcor-online.net!news.arcor.de.POSTED!not-for-mail From: "Dmitry A. Kazakov" Subject: Re: Loops and parallel execution Newsgroups: comp.lang.ada User-Agent: 40tude_Dialog/2.0.15.1 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Reply-To: mailbox@dmitry-kazakov.de Organization: cbb software GmbH References: <4d3eeef7$0$6879$9b4e6d93@newsspool2.arcor-online.net> <4d3f0a1d$0$6993$9b4e6d93@newsspool4.arcor-online.net> <1ge2i0esmav4i$.1jv4tflkkh9rf.dlg@40tude.net> <4d3f4985$0$6774$9b4e6d93@newsspool3.arcor-online.net> Date: Wed, 26 Jan 2011 10:04:07 +0100 Message-ID: <18u0kz3rdeadl.19kvrw0a9kqd2$.dlg@40tude.net> NNTP-Posting-Date: 26 Jan 2011 10:04:07 CET NNTP-Posting-Host: a549366b.newsspool4.arcor-online.net X-Trace: DXC=?h On Tue, 25 Jan 2011 23:07:01 +0100, Georg Bauhaus wrote: > On 1/25/11 10:32 PM, Dmitry A. Kazakov wrote: >> The Occam's par-statement could be a better candidate, but I don't see how >> this could be useful under a modern general-purpose OS with their >> "vertical" parallelism, when each task is assigned to one core. The thing >> you propose is "horizontal" parallelism, when a task/process would run on >> all cores simultaneously. Inmos' Occam ran under no true OS, and the >> processor architecture was well suited for such ad-hoc parallelism. Modern >> processors are very different from T805 and I doubt that they would allow >> an efficient implementation of this. > > I have recently seen small boards carrying one processor each > that could be connected to one another on all sides, IIRC. > What matters thens is, I think, the efficiency of > (a) distribution of small computation, and > (b) the delivery of results at some nodes. The Parix OS (actually a monitor) did that. E.g. if you called, say, "printf" in a node which didn't have a direct link to the server (the server was an MS-DOS PC or a Solaris workstation), the output would be routed to the node connected to the server and from there to the server which printed the output. > Is it therefore so unthinkable to have something like a transputer > these days? I saw them too. BTW, they are in some sense a step back comparing to the level Inmos arrived before its fall. They introduced a programmable TP-link switch, so that you could reconnect the network of transputers on the fly. But the problem is. I really see no use for the par-statement or alike. The main argument against par is that using threads causes to much overhead. If the argument stands, I mean if you don't have very long code alternatives running in parallel for seconds, then using a mesh of processors would make things only worse. The overhead to distribute the code and data over the mesh of processors is much bigger than doing this on a machine with shared memory (multi-core). There certainly exist examples of long independent code alternatives, but I would say that most of them are constructed or marginal. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de