Path: utzoo!attcan!uunet!super!udel!gatech!ncar!ames!necntc!mirror!rayssd!ukma!david From: david@ms.uky.edu (David Herron -- One of the vertebrae) Newsgroups: comp.sys.amiga Subject: Re: Dhrystone Message-ID: <10170@s.ms.uky.edu> Date: 27 Aug 88 15:19:14 GMT References: <8808180050.AA05343@cory.Berkeley.EDU> Reply-To: david@ms.uky.edu (David Herron -- One of the vertebrae) Organization: U of Kentucky, Mathematical Sciences Lines: 45 In article <8808180050.AA05343@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: > >:In article <8808150554.AA14630@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: >:> This is why such benchmarks are ludicrous, when people fine-tune >:>the benchmark and/or compiler to make the benchmark look better. I won't >:I think your comment is the ludicrous thing here. > Uh huh, you haven't thought the thing through have you? Let me >explain it more carefully: How large a percentage increase in speed do you >think you will get by replacing a subroutine-strcpy() with an inline-strcpy() >(etc...) ??? Matt, Matt, Matt... calm down ... Have you ever read the original Dhrystone article? The guy who came up with Dhrystone did all the right things make sure it used a proper mix of statement types. (Well ... he surveyed the programs written by first semester Pascal students to get his data ...) > Properly, the idea is to repeat the test on a whole shitload of >programs (that were not designed specifically to make a benchmark look good), >get the mean/average/whatever, and compare that relative speed increase to >the relative speed increase in the benchmark by the inline code. I don't think the art of benchmarking has improved to the point where someone can properly say what you just said. With larger programs it's harder to be able to say things about them with confidence. > Does that answer you question? I am not tarring either Lattice or >Manx, but pointing out two things people do not seem to understand about >benchmarks. (1) Never fine tune a benchmark, and (2) Benchmarks are >incredibly difficult to write if written properly. It didn't sound to me as if anybody changed the benchmark. Merely that Lattice put a global optimization into their compiler to make strcpy and friends into inline functions. Maybe they had in mind soley the idea of improving their dhrystone rating and saw that a lot of dhrystone was string copying. (It's been awhile since I read dhrystone so I don't remember what the perentage was for string manipulation). But so what? Strings get copied all the time in programs, so this is also a useful general improvement. -- <---- David Herron -- The E-Mail guy <---- ska: David le casse\*' {rutgers,uunet}!ukma!david, david@UKMA.BITNET <---- Problem: how to get people to call ...; Solution: Completely reconfigure <---- your mail system then leave for a weeks vacation when 90% done.