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 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,1a44c40a66c293f3 X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news3.google.com!news4.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local01.nntp.dca.giganews.com!nntp.comcast.com!news.comcast.com.POSTED!not-for-mail NNTP-Posting-Date: Tue, 06 Mar 2007 00:04:59 -0600 From: tmoran@acm.org Newsgroups: comp.lang.ada Subject: Re: PAR (Was: Embedded languages based on early Ada) References: X-Newsreader: Tom's custom newsreader Message-ID: Date: Tue, 06 Mar 2007 00:04:59 -0600 NNTP-Posting-Host: 67.164.83.70 X-Trace: sv3-MkywKL5emdHdxAR9eULldRAZ4fw2ET9Or9g7y7g0tEnmASDWE5rsY9N2elaRGYL2tLTfc1bNBjzEPer!Jv3hLcZHvw+xsfn2OnQgDorvwGZFv7xjMBY8TxZk86ff6CUXDSzB3sqCcny/4slGNw3n3p2pqf8M!XGpIPeLGKEWrLQ== X-Complaints-To: abuse@comcast.net X-DMCA-Complaints-To: dmca@comcast.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.34 Xref: g2news2.google.com comp.lang.ada:9707 Date: 2007-03-06T00:04:59-06:00 List-Id: > If you can persuade programmers to use "par" unless they explicitly > *need* sequential execution, a great many statements will be marked > as concurrent. Numeric codes will use "par" in the computational > core, as well as outer layers of execution. When "virtual memory" was new some programmers thought about their program's access patterns and found that VM was a great simplification. Other programmers simply said "oh, good, I can write my program to randomly access many megabytes, though the physical memory is only a few hundred kilobytes." Those programs were a disaster. Nowadays, of course, very few people write programs that don't in fact fit inside physical memory. I suspect we'll see a similar thing with multi-core: some will carefully consider what they are doing and it will be good; others will just say "oh, good, I can multiply an m x n and an n x p matrix using m x p threads", and it will be bad. Meanwhile the hardware will develop to automatically do more and more hidden concurrency. If programmers think of "par" as "I've carefully analyzed this algorithm and it may be run in parallel" that's good. If they think of "par" as "I want you to run this in parallel", I think that would be a bad mindset. Explicit Ada tasks are more like the latter. My $.02