From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Original-To: caml-list@sympa.inria.fr Delivered-To: caml-list@sympa.inria.fr Received: from mail3-relais-sop.national.inria.fr (mail3-relais-sop.national.inria.fr [192.134.164.104]) by sympa.inria.fr (Postfix) with ESMTPS id F0AB67EE99 for ; Sun, 22 Dec 2013 13:43:26 +0100 (CET) Received-SPF: None (mail3-smtp-sop.national.inria.fr: no sender authenticity information available from domain of jeffschultz@runbox.com) identity=pra; client-ip=91.220.196.211; receiver=mail3-smtp-sop.national.inria.fr; envelope-from="jeffschultz@runbox.com"; x-sender="jeffschultz@runbox.com"; x-conformance=sidf_compatible Received-SPF: Pass (mail3-smtp-sop.national.inria.fr: domain of jeffschultz@runbox.com designates 91.220.196.211 as permitted sender) identity=mailfrom; client-ip=91.220.196.211; receiver=mail3-smtp-sop.national.inria.fr; envelope-from="jeffschultz@runbox.com"; x-sender="jeffschultz@runbox.com"; x-conformance=sidf_compatible; x-record-type="v=spf1" Received-SPF: None (mail3-smtp-sop.national.inria.fr: no sender authenticity information available from domain of postmaster@aibo.runbox.com) identity=helo; client-ip=91.220.196.211; receiver=mail3-smtp-sop.national.inria.fr; envelope-from="jeffschultz@runbox.com"; x-sender="postmaster@aibo.runbox.com"; x-conformance=sidf_compatible X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhYCAA7etlJb3MTTnGdsb2JhbABYvVeBEhYOAQEBAQEGDQkJFCiCJQEBAQQ4QAEQCxgJFg8JAwIBAgFFEwEFAgEBh2sBEwUBw08BhykXjldOBxaEIAEDmBeGRY8Q X-IPAS-Result: AhYCAA7etlJb3MTTnGdsb2JhbABYvVeBEhYOAQEBAQEGDQkJFCiCJQEBAQQ4QAEQCxgJFg8JAwIBAgFFEwEFAgEBh2sBEwUBw08BhykXjldOBxaEIAEDmBeGRY8Q X-IronPort-AV: E=Sophos;i="4.95,531,1384297200"; d="scan'208";a="42020375" Received: from aibo.runbox.com ([91.220.196.211]) by mail3-smtp-sop.national.inria.fr with ESMTP/TLS/AES256-SHA; 22 Dec 2013 13:43:26 +0100 Received: from [10.9.9.206] (helo=mailfront02.runbox.com) by bars.runbox.com with esmtp (Exim 4.71) (envelope-from ) id 1VuiNQ-0007sw-FJ; Sun, 22 Dec 2013 13:43:24 +0100 Received: from 60-242-133-145.static.tpgi.com.au ([60.242.133.145] helo=[192.168.6.5]) by mailfront02.runbox.com with esmtpsa (uid:803928 ) (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.76) id 1VuiNI-0003GX-TC; Sun, 22 Dec 2013 13:43:17 +0100 Message-ID: <52B6DE5E.5080503@runbox.com> Date: Sun, 22 Dec 2013 23:43:10 +1100 From: Jeff Schultz User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: jon@ffconsultancy.com CC: caml-list References: <20131219224727.GA14006@annexia.org> <089e01cefebd$0e12f300$2a38d900$@ffconsultancy.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Caml-list] Question about garbage collection and impact on performance On 22/12/2013 14:04, David Sheets wrote: > On Sun, Dec 22, 2013 at 2:25 AM, Jon Harrop wrote: >> Richard Jones wrote: >>>> My personal impression is that the question is not that well-posed: >>>> - if you assume infinite memory, you don't actually need a GC (and for >>>> any input you can tweak the GC setting to make sure no collection >>>> happens) >>> >>> How could "infinite" memory be implemented without affecting the runtime >> of programs on such a machine? >> >> I guess O(1) lookup would actually be O(n^(1/3)) due to that speed of light >> thing. ;-) > > I think there are some fundamental limits to information density in > the local universe. I reply here, though, to propose that the lookup > would be O(n^(1/2)) because, locally, space is Euclidean. I'm not sure > how you got the 1/3 exponent. Eight times as much memory, uniformly packed in three dimensions, is at most twice as long in any one dimension. However, IIRC, Gene Amdahl observed that the limiting characteristic of memory size versus speed is actually the surface area of the sphere containing the memory, because that controls heat dissipation. This gives an asymptotic square root law. Various assumptions could challenge that, but not as long as memory consumes power in proportion to its size. Jeff Schultz