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Up Topic Rybka Support & Discussion / Rybka Discussion / Quick Question
- - By ChessStar (*) Date 2007-12-31 16:50
When I increase my hash to 2048 I get 17.9 ply; 234kn/s however when I lower hash to say 94mb i get 14.6 ply; 322 kn/s.  Which number should I worry about?  Is the lower hash doing better for a 5 min game?
Parent - - By Fulcrum2000 (****) Date 2007-12-31 17:04
2 Gb hash for a 5min game is total overkill. So use 1GB or 512 MB. Might be the 2 GB setting caused some disk trashing and hence worse performance.
Parent - - By ChessStar (*) Date 2007-12-31 17:17
But i have 4gb of ram using windows xp x64 pro as well! so do i look for the higher PLY? or KN/S? and is there a easy way to test to see how good each has does?
Parent - - By Fulcrum2000 (****) Date 2007-12-31 17:57 Edited 2007-12-31 18:17
Ok, didn't read your first post well enough. The kns (and ply depth) you get is dependent on the position. As a quick test you could measure the time it takes to get to depth 19 or so with different hash sizes from the starting position. Make sure you repeat this test several times as it might vary between runs.

But like I set this is irrelevant for 5min games as the 2GB will never get filled in that short timeframe anyway.
Parent - - By Jessica (**) Date 2007-12-31 18:04
What about leaving computer running over night on playchess?  Wouldn't hash get filled then?
Parent - - By turbojuice1122 (Gold) Date 2007-12-31 18:10
Generally speaking, the hash will be cleared at the start of each new game.  Also, the "filling" is a random process--even when it's not filled, some stuff will often be over-written.  The Shredder GUI has a neat way of seeing this process taking place.
Parent - - By ChessStar (*) Date 2007-12-31 18:33
Okay but didn't Vas say that there is no such thing of too much hash?
Parent - By turbojuice1122 (Gold) Date 2007-12-31 19:02
Yes, and he would know such things.  However, I didn't give any indication of the opposite, either.  The more hash one has, the lower is the likelihood that some helpful data get overwritten.
Parent - By Banned for Life (Gold) Date 2007-12-31 22:28
Rybka's node count does not seem to count positions that are found in the hash table so the comparison between different hash sizes is probably not really valid. Also, hash is always a power of two for current Rybkas, so 94 MB is really 64 MB. If you are not experiencing disk activity with a 2GB hash, this will be your strongest setting (but not by much).

Parent - By Vasik Rajlich (Silver) Date 2008-01-03 14:37
If you're getting a consistent NPS drop from 322 kn/s to 234 kn/s, then the increased hash size is causing paging on your system and you should use a smaller one.

Up Topic Rybka Support & Discussion / Rybka Discussion / Quick Question

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