Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: Notesfiles $Revision: 1.7.0.10 $; site ccvaxa Path: utzoo!watmath!clyde!cbosgd!ihnp4!pur-ee!uiucdcs!ccvaxa!preece From: preece@ccvaxa.UUCP Newsgroups: net.lang Subject: Re: Efficiency of Languages (and co Message-ID: <800003@ccvaxa> Date: Wed, 6-Nov-85 12:31:00 EST Article-I.D.: ccvaxa.800003 Posted: Wed Nov 6 12:31:00 1985 Date-Received: Fri, 8-Nov-85 07:25:36 EST References: <189@opus.UUCP> Lines: 38 Nf-ID: #R:opus.UUCP:189:ccvaxa:800003:000:1785 Nf-From: ccvaxa.UUCP!preece Nov 6 11:31:00 1985 [Quoted from a posting responding to a complaint that algorithm analysis tended to consider architectural rather than computational issues. I don't have the name of the original author.] > On the contrary, analysis of complexity of algorithms is generally done > with considerable care to separate these issues and identify the > assumptions about architecture implied by the algorithm. If you're not > accustomed to reading in the area, you may find yourself a little > befuddled because you don't understand some of the assumptions commonly > left implicit. > Dick Dunn {hao,ucbvax,allegra}!nbires!rcd (303)444-5710 > x3086 ---------- Well, you both missed the major architectural assumption in the examples you were arguing about, which is that the number of compares is a reasonable measure of cost. This assumption is usually mentioned in texts on the subject. Certainly in many cases there are other, more appropriate measures (in sorting, for instance, the cost of moving data may sometimes be a much larger factor than the cost of the compares). You also both missed the point that throwing N processors at a problem does not change its complexity -- all those compares are still being done SOMEWHERE -- even though it does change the elapsed time to completion (again raising the question of what is a useful measure of complexity). Overall I'd have to say that the first author was more correct: the common conception of algorithm analysis does tend to include major architectural assumptions that may not be valid for unconventional and innovative architectures. Those assumptions ARE usually considered by those who write in the discipline, but are often ignored by those who have merely studied it. -- scott preece gould/csd - urbana ihnp4!uiucdcs!ccvaxa!preece