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: 103376,7272aa7508a3d83f X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!newshub.sdsu.edu!elnk-nf2-pas!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!newsread3.news.pas.earthlink.net.POSTED!a6202946!not-for-mail From: "Jeffrey R. Carter" Organization: jrcarter at acm dot org User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: pointer questions References: <19cfb$4361207d$4995001$19541@ALLTEL.NET> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Message-ID: Date: Wed, 02 Nov 2005 03:46:41 GMT NNTP-Posting-Host: 67.3.222.101 X-Complaints-To: abuse@earthlink.net X-Trace: newsread3.news.pas.earthlink.net 1130903201 67.3.222.101 (Tue, 01 Nov 2005 19:46:41 PST) NNTP-Posting-Date: Tue, 01 Nov 2005 19:46:41 PST Xref: g2news1.google.com comp.lang.ada:6105 Date: 2005-11-02T03:46:41+00:00 List-Id: Dr. Adrian Wrigley wrote: > This is exactly the situation. The "Things" were about 36 bytes each > and I changed to having around 20 million pointers to things. > Single bit errors in pointers had a much more significant effect > than single bit errors in "Things" (which tended to be ignored > for various reasons). Right. I don't think I'd ever want to consider a continually running program with 20 million pointers. What did that buy you over the single-pointer version? > well speculated! (was it so unclear?) Thanks. I wasn't clear what was causing the crashes at 1st. With a little more thought, it seemed likely it was dereferencing a pointer with a flipped bit. > Another "feature" I observed was that files could stay cached by the OS > for months, and accumulate the occasional single-bit error. But when you > evict the cached pages and read the data again, the errors disappear. > Plenty of scope for very rare Heisenbugs. Interesting. It's not something you normally have to think about; most programs don't run for that long. I remember a noticeable # of bit errors during a solar maximum about 1980, but don't recall it repeating in 1991 or 2002. -- Jeff Carter "In the frozen land of Nador they were forced to eat Robin's minstrels, and there was much rejoicing." Monty Python & the Holy Grail 70