Author: Robert Hyatt
Date: 15:21:06 11/06/01
Go up one level in this thread
On November 06, 2001 at 14:10:50, José Carlos wrote: >On November 06, 2001 at 13:54:02, Joshua Lee wrote: > >>Tablebases are too slow. TB's slow down search to a rediculous point and will >>make a 1Ghz machine think it's a P-90. >>Is there any work being done to improve function of probing or what can be >>changed about tablebases or anything that works with the tablebases to change >>this? I don't have SCSI but i have two drives which are amongst the fastest IDE >>drives you can buy 8.2 and 8.9ms access time, you can get SCSI drives that hover >>around 4.9ms and up past 10,000 rpm. This i believe would'nt change the Search >>hit. This probably has more to do with the first time the TB's are Accessed the >>Program continues to Look Even if it didn't find anything to help so at ply's >>1-20 Which will come by fast in the endgame are bogged down and now take much >>longer. >> >>What exactly is the program looking at and how are the positions stored? I can't >>imagine a bunch of EPD's for KPPKPP. >>I would think that the compression and how the program looks for the position to >>be it's Sore Spot. > > I don't know the answer to your question, but tablebase access can kill your >program's performance if you probe too much, and can improve a lot if you probe >only when you need it. > So once you get it working, you have to make it work fast. Not easy at all. > > José C. If he was talking about writing his own program, the first trick to notice is that if you reach N pieces, and you have N piece tables, you probe _only_ following the capture that takes you down to N pieces. If you don't hit there, you do _not_ probe at every position past that point as you _still_ won't have that table and the overhead is wasted. You probe only after a capture or pawn promotion, and nothing else. Once you get that right, then you start limiting the depth you probe at, which directly controls how many I/O reads you do. The more you limit the probe depth, the less the performance penalty. You have to strike a balance between speed and probing... Overboard in either direction hurts.
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