Author: Ed Trice
Date: 15:58:22 02/11/04
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Hi martin, Just my own observations about pawn hash tables and Gothic Chess. First, your other hash tables will be effective tree-reducers, pawn hash tables will not be. Pawn hash tables are "time savers". They are for the high frequency hits that are color independent. You can save an expensive scoring calculation if you can encounter the structure often enough. Factoring in some of the other parameters you mention, while "good knowledge", in practice, might not be worth the expense of the implementation. On the Gothic Chess board represented in Gothic Vortex, the pawn hash table is set up to be 1/8th the size (in RAM) of the other two hash tables combined. It has a payoff of about 10-20% in terms of overall time-to-depth, and about 5-10% in terms of nodes/second. >on my long todo list for my program, the item "pawn hashing" has slowly but >steadily floated upwards. now it's on top. so: how large is your pawn hashtable >(in # of entries)? how large are your entries? i'm using bitboards, and it seems >to me that my entries will be huge, e.g. if i want to save some simple stuff >like > >- passers >- connected passers >- isolated pawns >- doubled pawns >- backward pawns >- blocked pawns > >that would be 6x8 = 48 bytes; perhaps times 2 for each side (or i could pop >black and white pawns in the same bitboard, and & it with the black/white >bitboard to save space). still, that's already 48 bytes and i guess i could save >some more stuff if i thought about it a bit longer :-) >is that a reasonable size for a pawn hash entry? > >cheers > martin
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