Author: Robert Hyatt
Date: 07:41:27 12/19/03
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On December 19, 2003 at 01:21:45, Jouni Uski wrote: >After installing more RAM to my Pentium 2,4 GHz I tested Fritz8 in some test >suites with 128MB and 384MB hash (time limit was 10 minutes and positions quite >hard = average solution times around 3-5 minutes): to my surprise >average solution time was shorter with 128MB! Why? Absolutely no hard disk >swapping with 512MB total RAM! > >Jouni Hashing is based on random numbers. Which means the result of using them is going to have a bit of randomness as well. Sometimes bigger hash slows a program down, because it makes the search more accurate, which might make it a bit slower. But accuracy and speed don't necessarily match up so it is not easy to say "this is slower, so it is worse." Also, there are hardware considerations. The size of the TLB for example. If you blow that out, you make your memory access time go from maybe 150ns to 3X that. Since hash tables are addressed randomly, this is a real possibility. IE the opteron I was using earlier this week has just over 1000 TLB entries. That lets me address 1000 * 4K very quickly. Anything beyond that sees slower memory access times.
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