Author: Robert Hyatt
Date: 13:20:01 11/22/04
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On November 22, 2004 at 13:02:36, Martin Baumung wrote: >On November 22, 2004 at 11:23:53, Robert Hyatt wrote: > >>On November 22, 2004 at 10:48:02, Steve Maughan wrote: >> >>>I have a relatively new machine that has a P4 with Hyperthreading. I've >>>recently installed Shredder 8 and Gandalf 6. When playing a match I switched to >>>the Task Manager to look at the memory usage and noticed that when Gandalf was >>>thinking, according to the TM, it was only using 50% of the CPU while Shredder 8 >>>was using 100% (both had Ponder = off). On further investigation Shredder was >>>using 2 threads in the engine. Looking at the speed, both were getting >>>approximately the same nps which is inline with other machines I have tested >>>them on. >>> >>>So the question is - does the Task Manager report the CPU resource usage >>>incorrectly in this situation i.e. 50% = 100% usage of 1 processor? I'm >>>reasonably sure that this is the case but wanted to check. >>> >>>Thanks, >>> >>>Steve Maughan >> >> >>It is difficult for _any_ program to figure out what is going on, since >>hyper-threading makes the O/S think there are two equal CPUs, when there really >>is not... for engine vs engine you should turn it off in the BIOS... > >maybe a silly question, but why should one turn HT off - at least for engine >matches without pondering? So far I didn't encounter any problems. I've only >tried Shredder 8, but it gets a few extra nps with HT. > >Cheers, > >Martin Some engines will see the second "processor" and use it. That creates an imbalance. If you do ponder-on which is the only way I run, then there are further ways for the two programs to interfere with each other. The one that is the best-behaved in cache will run on a processor that appears to be significantly faster than the processor for the program that is not so well behaved...
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