Author: Dann Corbit
Date: 14:11:57 02/11/04
Go up one level in this thread
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?
The pawn hash table only holds a hash of [the pawn positions, colors, e.p. flag
and (usually) the king position.] So one 64 bit number gets stored as the
position in the array and the key {of 64 - address bits.}
The key is used to know that your hash does not collide.
You also store the overall pawn score (most people use a signed short between
+32766 and -32767). You add up all of the terms above into a single value for
this score.
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