Author: William Penn
Date: 18:43:25 08/31/03
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 Gotcha! Thanks. I needed that clarified. I have indeed noticed that I get about 1 ply deeper in a certain amount of time (say 1 hour) when using maximum hash on this box. I'll run some more tests and confirm it. Another important point to me is... Preferably the user should be able to access the best analysis "so far" in Infinite Analysis mode (or other modes), but that option apparently isn't available. Thus I must sit & wait & hope that it will deign to contact me with its internal results before I go to bed. It's unpredictable. Sometimes it takes a few minutes, sometimes several hours before the next analyis clip appears in the engine window. Is there something I'm overlooking? Is there any way to access the best analysis to date without stopping ongoing analysis in Infinite mode, or some way to make it spit out those clips more frequently? I'd like to see a clip about every 10-15 minutes, but at least one per hour at a minimum!? Thanks, WP
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