Author: Michael P. Nance Sr.
Date: 10:20:48 09/01/03
Go up one level in this thread
On August 31, 2003 at 21:18:58, Ross Boyd wrote: >On August 31, 2003 at 19:44:28, William Penn wrote: > >>The more hash I allocate, the slower the kN/s speed. Thus 4MB (the minimum) is >>the fastest in my tests, typically about 450kN/s. If I increase that to say >>256MB hash, the speed slows down to about 400kN/s. The more I increase hash, the >>slower the kN/s speed. >> >>The kN/s speed peaks, then eventually starts to decrease. How long this takes >>depends on the amount of hash. However in my tests, the long term speed >>advantage of bigger hash never catches up with the long term speed obtained with >>smaller hash. Thus I don't see any advantage whatsoever to using a hash table! >>The opposite seems to be true!? >> >>I'm using the Shredder7 GUI, Shredder 7.04 UCI engine, AMD XP Athlon 2400+/640MB >>RAM (608MB available). The GUI says the maximum I can allocate to hash is about >>455MB, so I'm not near the limit. Of course I'm using fairly common practical >>positions for these tests in Infinite Analysis mode, and the above indicated >>results are typical. >> >>I get very similar results running Shreddermarks with different size hash. The >>more hash, the lower the Shreddermark and corresponding kN/s. >> >>Now, will someone please refute this, or explain what I'm missing or >>overlooking? Thanks! >>WP > >Increasing the hash size will tend to lower the NPS in most engines. > >Its kind of hard to explain why this is so... but I'll try. When an engine gets >a hit in the hashtable it often cuts short the amount of exhaustive quiescence >searching where NPS tends to go high. Nearer the root there is generally more >overhead involved, with for example, more sophisticated move ordering etc... >whereas the move ordering at the QS tends to be cruder and hence faster. > >Anyway, its not a bad thing.... > >What is more important is the total number of nodes visited to get to a certain >depth. You will see that increasing hash size will tend to reduce the tree... >and therefore (even though NPS drops slightly) the actual time taken to get to a >given depth is reduced (usually). > >Time how long Shredder takes to get to a given depth, and also the total nodes >visited, with various positions for two hash sizes. You'll see the true benefit >of increasing the hash size. > >If you turn off the hash altogether you'll see the NPS increase a lot... but its >not going to play stronger that's for sure... > >So, NPS is not a measure of strength. Really, its only useful for comparison >purposes of the same engine with the same hash size on 2 different PCs. > >Hope this makes sense... > >Ross I will tell You this,when I demisish the Hash,(32,64,128,ect),I get beat. When I go "FULL THROTTLE",or optimise the Hash,(819), I usually beat the same Box and Program that I couldn't beat with a lower Hash setting.>>>>Mike
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.