Author: Robert Hyatt
Date: 14:51:00 11/27/00
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On November 27, 2000 at 15:52:04, Uri Blass wrote: >I found in my engine-engine games that the number of nodes per second was too >low and I suspected that something is wrong with it so I decided to download >Fritz6light as the only active engine. > >Hiarcs7.32 was the only active program and Fritz6light was the only active >engine(32 mbytes hash tables). > >I found the same behaviour so I decided to check the numbers of nodes and the >times in the position after 1.a3 a6 2.e4 > >I got the following results on my PIII450: >20 seconds 4737 knodes >56 seconds 13024 knodes > >This means only slightly more than 200 knodes per scond and it seems too low >because I know that the normal knodes per second is bigger. > >I decided to restart my computer and after doing it I found the following >results at the same conditions(Hiarcs7.32 is the only active program and >Fritz6light is the only active engine with 32 mbytes hash tables). > >14 seconds 4737 knodes. >41 seconds 13024 knodes. > >1)Can someone explain the reason that my computer became faster after >restarting? > >2)Is there a way to know that my computer is slower without doing a test like >this test. > >I want to know if it is slower during an engine-engine game without giving it >the position after 1.a3 a6 2.e4 and checking the times. > >I can only suspect by looking at the number of the nodes per second because it >is possible that the number is smaller because of different position. > >Uri The most common reason is a problem with how the problem is laid out in memory. Since memory is direct-mapped into sets in cache, it is possible to get a memory layout where many memory pages map to the same cache set. Overloading that set and under-utilizing other sets. This is a tough problem to overcome. There is a memory layout algorithm that is often called "page coloring" that prevents this. I don't know whether windows uses it or not... This reboot/test/reboot/test is a pretty common thing to see at computer chess events. :)
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