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Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connectionsPath: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail From: anton@mips.complang.tuwien.ac.at (Anton Ertl) Newsgroups: comp.lang.forth Subject: locals slowness in sf and vfx (was: SEND+MORE=MONEY) Date: Thu, 09 Feb 2023 17:13:54 GMT Organization: Institut fuer Computersprachen, Technische Universitaet Wien Lines: 30 Message-ID: <2023Feb9.181354@mips.complang.tuwien.ac.at> References: <78cfcd0a-5bc4-4584-8a92-9e8005a0e306n@googlegroups.com> <87ttzvzmmb.fsf@nightsong.com> <2023Feb9.084758@mips.complang.tuwien.ac.at> <138b28de-6f2a-449b-9279-629f3c17a03bn@googlegroups.com> <2023Feb9.115420@mips.complang.tuwien.ac.at> Injection-Info: reader01.eternal-september.org; posting-host="4a23064dba6cc3b448d0d7b13f318f12"; logging-data="790587"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/ZWsfxH1vfQXUR3xommyNa" Cancel-Lock: sha1:LcXNgSskggvHCsYhY6TXgCioi6Y= X-newsreader: xrn 10.11 Bytes: 2373 anton@mips.complang.tuwien.ac.at (Anton Ertl) writes: >The lxf result demonstrates that locals can be implemented much more >efficiently than in VFX or in SwiftForth. One reason for the slowness of VFX and SwiftForth is that they produce many more branch mispredictions (on Zen3): lxf sf 4.0.0 RC52 vfx64 5.11 RC2 1_661_643_918 5_213_828_602 6_905_863_327 cycles:u 5_033_144_481 11_408_344_624 9_084_604_276 instructions:u 4_371_603 70_048_027 72_169_382 branch-misses http://www.complang.tuwien.ac.at/forth/programs/sendmore.fth A misprediction typically costs 20 cycles, so the 66M-68M additional mispredictions cost 1.3G-1.4G cycles which does not explain all of the slowdown, but a good part of it. These mispredictions are caused by the technique of pushing an additional return address that returns to other code than that where the last call came from. The hardware return stack for branch prediction was introduced at least 25 years ago, it's time that Forth systems accept that reality and let go of this technique. - anton -- M. Anton Ertl http://www.complang.tuwien.ac.at/anton/home.html comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html New standard: https://forth-standard.org/ EuroForth 2022: https://euro.theforth.net