Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!mintaka!ai-lab!life!burley From: burley@albert.gnu.ai.mit.edu (Craig Burley) Newsgroups: comp.arch Subject: Re: Amdahl's Law vs Amdahl/Case Rule (Was: Fast I/O) Message-ID: Date: 22 May 91 08:03:15 GMT References: <97b302n807vo01@JUTS.ccc.amdahl.com> <13096@pt.cs.cmu.edu> <860@cadlab.sublink.ORG> Sender: news@ai.mit.edu Organization: Free Software Foundation 545 Tech Square Cambridge, MA 02139 Lines: 19 In-reply-to: martelli@cadlab.sublink.ORG's message of 21 May 91 09:24:08 GMT In article <860@cadlab.sublink.ORG> martelli@cadlab.sublink.ORG (Alex Martelli) writes: (the crucial reason why you never get as much benefit as "common sense" would suggest, from specialized coprocessors, vectors, parallel...). Never say never! You should use the rule to find out about how much benefit to EXPECT, especially on a "traditional" problem. But on some problems, parallelization (or even coprocessors, I suppose) can have a superscalable (is this the right word?) effect on performance. E.g. a program which runs in X units of time on a single processor can run in X/10 units of time on eight parallel processors. (Or even less time.) But I think this works only for programs including solution-space searches as critical elements of their algorithms. -- James Craig Burley, Software Craftsperson burley@gnu.ai.mit.edu