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=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!news.glorb.com!Xl.tags.giganews.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail NNTP-Posting-Date: Sun, 05 Apr 2015 08:57:08 -0500 From: Dennis Lee Bieber Newsgroups: comp.lang.ada Subject: Re: Languages don't matter. A mathematical refutation Date: Sun, 05 Apr 2015 09:57:08 -0400 Organization: IISS Elusive Unicorn Message-ID: References: <87h9t95cly.fsf@jester.gateway.sonic.net> <04f0759d-0377-4408-a141-6ad178f055ed@googlegroups.com> <871tk1z62n.fsf@theworld.com> <87oan56rpn.fsf@jester.gateway.sonic.net> <877fts7fvm.fsf@jester.gateway.sonic.net> <87twwv66pk.fsf@jester.gateway.sonic.net> X-Newsreader: Forte Agent 6.00/32.1186 X-No-Archive: YES MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Usenet-Provider: http://www.giganews.com NNTP-Posting-Host: 108.68.178.130 X-Trace: sv3-a5Dy/B/uYT/zKKDkjbx1ILkFNSNYJGXdg/B9rR7jb3R9PrO+oQXR/j2C6ZGvrLd+UmJh7dTcUdINhkL!Fkbo4HXE/PhRrw5wP9cp2jpnf8r8Mzc5rSUIQ8KCX3P5gW2QdH4Djk7Npy5MQe8hE4ywu/9qsyfb!a+FcUF18aMPwINWZ9zZ61nB5aa2R 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: 1.3.40 X-Original-Bytes: 3273 Xref: news.eternal-september.org comp.lang.ada:25433 Date: 2015-04-05T09:57:08-04:00 List-Id: On Sat, 04 Apr 2015 12:20:39 -0700, Paul Rubin declaimed the following: >Dennis Lee Bieber writes: >>>How big and complicated do those programs tend to be, if you don't mind >>>my asking? Do they have a lot of complex decision paths? >> It's not decision paths so much as deterministic timing... If there is >> a possibility of an operation triggering an arbitrary garbage collection > >Yes, I can understand why a realtime system can't use gc. Writing >simple programs without gc isn't too difficult. Writing complicated >programs without gc often means spending a lot of effort on manual >memory management and debugging memory errors. So I'm wondering if the >programs you wrote that way were complicated and if yes, how you dealt >with this issue. > At present, I'm only on the fringe of things -- my 30 years at Lockheed were on non-realtime number crunchers that ran one or two days in advance of operations, for purposes of scheduling resources. My 2 years at GE Aviation has been more debug support -- though what I've encountered has been mostly the executive/device-driver layers; the end application tends to be provided by the client using the documented APIs of the executive. >In this case you may also have to consider the non-deterministic effects >of cache misses, if your cpu has cache memory; similarly for pipeline >stalls, serial multipliers, etc. It likely gets verified as part of the flight certification process. I do know that multicore processors aren't currently supported due to such conflicts. -- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/