Author: Vincent Diepeveen
Date: 17:58:33 09/12/03
Go up one level in this thread
On September 12, 2003 at 17:00:25, Gian-Carlo Pascutto wrote: minimum number of bits to store somehow either by index or non-index is 48 bits (1 = pawn, 0 = no pawn) + 16 bits ( 1 = white, 0 = black ) = 64 bits. So that is going to be massive overwriting. of similar structures at the same adress. Very poor for hash %. Skip bitboards. Just use Zobrist and AND. DIEP's pawnhashtable is like 4MB anyway and never bigger. I never understood those large sizes for pawn hashtables. Soon i can get rid of the thing completely when the last couple of hundreds of patterns get extra conditions, so getting difficult to cache. Then i can save out a potential penalty of 2 x 400ns, which in future perhaps will be too much anyway for a lookup :) >On September 12, 2003 at 16:53:44, Omid David Tabibi wrote: > >>assuming 'table_size' is a power of 2, the following two expressions are >>equivalent: >> >>address = key % table_size; >>address = key & (table_size - 1); > >That's exactly the problem. He generates his hashkeys by >taking the differnce of the white and black pawn bitboard. > >If you 'AND' off a piece of that, you're just cutting out a part >of your board - with massive hash collisions as a result. > >You want something more nonlinear. > >-- >GCP
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