Author: Tord Romstad
Date: 01:23:54 02/12/04
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On February 11, 2004 at 16:43:06, martin fierz wrote: >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? My entries are much bigger; currently 128 bytes. I store all of the above, as well as information like total number of pawns on black/white squares for each side, total number of blocked pawns on black/white squares, weak squares, open files, pawn storm stuff for use in positions with castling to opposite sides, and a classification of the central pawn structure. In my opinion, there is no reason to be afraid of having big pawn hash table entries, because you need very few of them. The pawn structure doesn't change that often. I've found that 256 entries is enough in my engine. Making the table bigger gives only a tiny speedup. Tord
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