Author: Charles L. Williams
Date: 07:06:51 04/15/99
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On April 15, 1999 at 09:36:51, Bruce Moreland wrote: > >On April 15, 1999 at 06:27:26, Ulrich Tuerke wrote: > >>On April 15, 1999 at 05:30:55, Rick Andrews wrote: >> >>>About how much weaker do chess programs play when playing against >>>each other on the same computer? >>>Thanks, Rick Andrews >> >>Assumed that when playing on the same computer/processor, pondering will be >>disabled.Also assumed that programs are doing essentially the same when >>pondering: expect the next move of the last PV and search. >>Pondering enabled can give theoretically a factor of 2 in performance when all >>guesses are hits (you have your and the opponent's time). In this theoretical >>extreme case pondering could make a difference of about 40 - 50 ELO points. >>In practice, there are less hits. So I arbitrarily guess that the difference >>could be 20 - 30 ELO points. > >A normal Windows program does its initialization stuff, then sits in a message >loop, waiting for stuff to happen. While it is sitting in the message loop it >is blocked, meaning that it is not using CPU. > >This model doesn't fit chess programs very well. They want to be doing >something all of the time, and the classic implementation involves a recursive >function, so you are off in this enormous call stack doing stuff all of the >time. > >It's possible to make this thing its own thread, or you can call a message loop >occasionally while searching. If it's not threaded or does not check for messages during the search, then the GUI is effectively disabled until the search is over. Threading, IMHO, is a good way to handle the search. The search can be halted at any time by checking a global variable before each eval. > >If "pondering" is turned off, the program should just sit there in the main >message loop between moves. I don't think that all of the programs do this. I >remember testing on a single machine a long time ago, and seeing NPS much >reduced even when the other program was sitting there doing nothing. > Maybe the program had set it's priority high to squeeze out more NPS while it was thinking. >Does anyone know of a program that for sure uses CPU even when it is not >thinking? > >bruce Chuck
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