Author: martin fierz
Date: 01:19:32 12/12/03
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On December 11, 2003 at 12:06:53, F. Huber wrote: >Hello! > >Since more than one week I´ve now a problem, which is really _strange_: > >Immediately after the release of my new ChestUCI version 3.0 I´ve got >a response of some chess friends, that this new version is constantly >slower than the last one (ver.2.8) by 8-10%. So I tested it myself on >my new system (Pentium-IV 2.66), but I couldn´t confirm that - I got >_absolutely identical_ solution times with this new version as with >all previous ones! >After some more tests we found out, that this 10% slowdown ONLY occurs >on AMD-processors - NOT on Intel-CPUs !? >And furthermore: the ´reason´ for this mysterious behaviour is not in >my own ´ChestUCI´ (written in Borland Delphi), but in ´Chest´ itself >(from Heiner Marxen), which is written in ANSI-C and modified by me >(only some additional file output!) for better communication with my >UCI-interface and compiled with MS-VC++ 6.0. > >So what has changed in ´Chest´ from 2.8 to 3.0? > >1) I´ve included a few improvements and corrections from newer source >files, which Heiner has sent me some time ago - but these were really >_minor_ changes: absolut nothing that could explain a slowdown of Chest! >(I´ve already emailed Heiner, but he also has no idea, how his small >changes could have such an effect - and furthermore _only_ on AMD-CPUs) > >2) I´ve added a few additional commands (file output) to Chest, but normally >these are not even executed at all - only if you really request them by >setting a special engine option. So also my own changes could not explain >this slowdown. > >What has NOT changed? > >1) I´ve _definitely_ NOT changed ANY compiler options! >I tested this again and again, and I´m absolutely sure about this. >Furthermore (since I´m not an expert in ´C´) I always compile(d) Chest >with the compilers default settings (of course ´optimized for speed´, >but that _is_ the default setting). > >2) The size of the EXE-file (´WinChest.exe´) has NOT changed - not even >a single byte! (no big surprise, since all changes were rather small) > >3) And most important: as I mentioned above - the execution times on >Intel-processors did NOT change at all !! > >Now, what have I tried? > >Within the last week I´ve exactly compared the new source code with the >old one and searched for any possible errors - no success! >Since I´ve no actual AMD-system I took my old one (AMD-K6/200MHz), which >showed the same ´slowdown´ effect, made dozens of small changes in Chest >(e.g. taking back some of the new changes) and recompiled it - no success! >Once it seemed that I had found a solution (at least on my old K6 it was >much faster again), but after having sent this new version to my friends, >they said: "NOT faster, even slower!" - so this AMD-K6 seems not to be >comparable with modern Athlons at all. > >And now I´ve really reached a point, where I have no further ideas, what >else I could try. :-(( >Since here are lots of experts, maybe someone will know a solution for >this strange problem - or at least could give an explanation for this >mysterious slowdown effect on AMD-CPUs. >(What I´m really angry about is not this slowdown itself - because those >AMD´s are anyway faster for chess than Intel´s - but the fact, that I >don´t know ´WHY?´. And as long as this question is not answered, there´s >still the bad feeling of ´maybe I´ve indeed made some error anywhere?´.) > >So hoping to get some ´good´ answers, ;-) >my best regards, >Franz. hi franz, i assume you are now using those virtualalloc functions instead of malloc? i found sometimes that this can make a performance difference, i don't remember it being 10%, but still - you could try replacing the virtualalloc with malloc again and see whether that is (part of) the problem. although, i found this on an intel CPU... of course, if you don't use virtualalloc you have this limitation of 256MB. cheers martin
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