Path: csiph.com!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Paul Rubin Newsgroups: comp.lang.forth Subject: Re: Parsing timestamps? Date: Wed, 09 Jul 2025 22:59:00 -0700 Organization: A noiseless patient Spider Lines: 25 Message-ID: <87ldowwpqz.fsf@nightsong.com> References: <1f433fabcb4d053d16cbc098dedc6c370608ac01@i2pn2.org> <2025Jul2.172222@mips.complang.tuwien.ac.at> <300ba9a1581bea9a01ab85d5d361e6eaeedbf23a@i2pn2.org> <4d440297d7e17251ebc50774bacfec73e184f9bc@i2pn2.org> <2025Jul5.104922@mips.complang.tuwien.ac.at> <6fd9f665e73ad93270fff88eca894ba69424cac7@i2pn2.org> <87a55dxbft.fsf@nightsong.com> <87y0swwtqt.fsf@nightsong.com> MIME-Version: 1.0 Content-Type: text/plain Injection-Date: Thu, 10 Jul 2025 07:59:01 +0200 (CEST) Injection-Info: dont-email.me; posting-host="9aa5980888cce665223eb2b8e83d190f"; logging-data="761711"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/d/LXOh/NgVJi44sgInzj7" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) Cancel-Lock: sha1:WEZQaPUBt7jMC+oFN1cQbT64QQY= sha1:Mrf3yYSEwKWBOwaJbpwP1t1hnIw= Xref: csiph.com comp.lang.forth:134004 minforth writes: > I don't do parallelization, but I was still surprised by the good > results using FMA. In other words, increasing floating-point number > size is not always the way to go. Kahan was an expert in clever numerical algorithms that avoid roundoff errors, Kahan summation being one such algorithm. But he realized that most programmers don't have the numerics expertise to come up with schemes like that. A simpler and usually effective way to avoid roundoff error swamping the result is simply to use double or extended precision. So that is what he often suggested. Here's an example of a FEM calculation that works well with 80 bit but poorly with 64 bit FP: https://people.eecs.berkeley.edu/~wkahan/Cantilever.pdf > Anyhow, first step is to select the best fp rounding method .... Kahan advised compiling the program three times, once for each IEEE rounding mode. Run all three programs and see if the outputs differ by enough to care about. If they do, you have some precision loss to deal with somehow, possibly by use of wider floats. https://people.eecs.berkeley.edu/~wkahan/Mindless.pdf