Author: Coxwell Strange
Date: 14:41:47 11/12/02
Go up one level in this thread
On November 11, 2002 at 22:44:48, Robert Hyatt wrote: >On November 11, 2002 at 21:33:24, Bob Durrett wrote: > >>On November 11, 2002 at 21:17:01, Robert Hyatt wrote: >> >>>On November 11, 2002 at 15:41:48, Bob Durrett wrote: >>>> >>>>I am a non-programmer but assume that all professional programmers know all >>>>about optimizers. Sounds like a good thing to have, anyway. : ) >>>> >>>>So far, we have been talking about the case where there is only one big program >>>>running on the computer and that is the chess engine [& GUI maybe]. But many >>>>people [I presume] also run Office or Word and maybe other software. I almost >>>>always have CB8 running when using Fritz, for example. Perhaps running several >>>>big programs at once would cause the operating system to be more busy? as a nonputer pro, all i have to contribute to this subject is the consistent observation that a 2 % reduction of puter resources equals a 1 % reduction in speed in a prorams time of search to depth... OS or other programs can therefor iimpact program speed, but how great of a variation in chess strength is doubtful at the current speed of todays puters. >>>> >>> >>>Yes, but the overhead for such is expected and all systems will lose a tiny >>>bit of time doing context switches. Some worse than others. But the usage >>>Vincent was describing makes no sense, as he said "one console program". >>> >> >>Not clear. Like multiple PCs but only one monitor and keyboard? Or, multiple >>processors with shared memory and shared monitor and keyboard? > >Multiple PCs is a whole different matter. Operating systems are not >distributed in such a cluster. Each node in the cluster runs its own unique >operating system copy. Not so in a SMP box where there is one OS scheduling >all the processors... > > > >> >>Not clear what Vincent was discussing in that case. Relevance to main question >>unclear. Could it be that operating systems might have more work to do in that >>case? If SMP, then communication between processors considered to be an >>operating system function? If so, how much % of total processor time for that? >> > >Zero basically. I have no idea what he was talking about either, and I won't >try to speculate. Other than to say that for a chess program, the O/S is _not_ >an issue. The efficiency of the compiler optimizer and the speed of the >processor are the two overwhelming points of significance... Windows, unix or >even DOS would make no difference whatever... > > >>Please forgive me if my ignorance regarding operating systems is showing. : ( >> >>> >>>>We have also been assuming that the computer would have ample RAM. However, >>>>maybe not everybody has an expensive computer with tons of RAM. There may be >>>>competition for the available RAM, and the OS would be one of the competitors. >>>> >>>>So, can the conclusions reached so far be extended to these cases too? >>>> >>> >>>No system pages efficiently, but that is a totally different issue to >>>operating system overhead in normal usage. >>> >>> >>>>Incidentally, why would the Fritz people write their program in assembly >>>>language, essentially bypassing an "optimizer"? Does it make enough difference >>>>to go to that much trouble? [Maybe the Fritz people think only in assembly >>>>language? : ) ] >>>> >>> >>> >>>Because you can do better than the optimizer. You design the program, so >>>you know more about the internals of the program. IE if you want to do some- >>>thing like wtm=!wtm; the optimizer has to handle cases where wtm can be >>>_any_ legal integer value. If I know that it is only zero or one, I can >>>change that to a much faster XOR instruction. Because I know something the >>>compiler doesn't. Ditto for lots of other common things. A switch. I don't >>>have to check for the "out-of-range" values, as I _know_ there will be none. >>> >>>etc... >>> >>> >> >>I may be asking a question no one can answer, but: "How much difference would >>that make?" "100 rating points?" > >Unknown. In the case of Cray Blitz, which I _did_ convert to mostly >assembly language, the CAL version (Cray Assembly Language) version was >about 5x faster than the best the optimizer could do with a pure FORTRAN >code. 5x is more than two doublings, so 100+ rating points is in the right >range... But the issue would be the actual speedup obtained. I know the >number for the Cray as Harry Nelson and I wrote the code and did the timing >comparisons. I haven't done it for the PC so anything I say would be pure >speculation. I've written a good bit of PC assembly code in the last few >months, but the raw architecture of the PC instruction set is simply not as >powerful as other architectures, the paucity of registers might make speedup >numbers like 5x much more difficult to obtain... that's why I am afraid to >speculate without anything to back it up... > > > > > > >> >>I'm still looking for a "bottom line" here, such as a conclusion or executive >>summary of findings, or whatever. >> >>Something profound, preferably. : ) >> >>Bob D. >> >> >>> >>> >>> >>> >>>>P.S. Note that I am trying to use plenty of smileys whenever I intend humor. >>>> >>>>Bob D. >>>> >>>> >>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>>>On November 11, 2002 at 13:02:44, Bob Durrett wrote: >>>>>>> >>>>>>>>Would the engine perform significantly better using that dedicated operating >>>>>>>>system? [As compared to using a commercially available OS] >>>>>>> >>>>>>>You can get an idea of how much time is used by the OS. On my computer I look >>>>>>>under Task Manager and it says: >>>>>>> >>>>>>>Image Name CPU Time >>>>>>>System Idle Process 6:19:14 >>>>>>>IEXPLORE.EXE 0:02:16 >>>>>>>msdev.exe 0:01:22 >>>>>>>Explorer.exe 0:00:53 >>>>>>>System 0:00:22 >>>>>>> >>>>>>>And so on. So I have over 6 hours of idle time, and the next biggest chunk of >>>>>>>CPU usage time was by Internet Explorer, of a whole 2 minutes. That means there >>>>>>>is 99.5% of the CPU time that could have been used by a chess program. So the >>>>>>>question is whether or not a 0.5% increase in speed is going to mean >>>>>>>"significantly better" results. I think not.
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