Author: Robert Hyatt
Date: 19:04:05 02/28/00
Go up one level in this thread
On February 28, 2000 at 20:28:56, Bruce Moreland wrote: >On February 28, 2000 at 17:04:13, William Bryant wrote: > >>I am curious, >>do you hash a different constant for each of the 16 possible ep squares, or >>simply a single constant if ep is possible. >> >>I have sixteen different values that are XOR'ed into the hash signature >>depending on which square is the ep square. >> >>It is intersting that Bruce made a comment about this a while back. He noted >>that the same opening position reached by a different order of moves will >>produce a different hash signature doing ep squares in this way. Therefore it >>does create a degree of inefficiency because (except for the ep move) the rest >>of the position may have already been evaluated and in the hash table. >> >>William >>wbryant@ix.netcom.com > >If you hash in en-passant square mindlessly you get a surprising amount of hash >inefficiency. > >1. e4 e5 2. c4 and 1. c4 e5 2. e4 produce the same position, and an en-passant >capture is not possible in either. Yet I bet that some people hash in the >d-file code in the first case and the e-file code in the second case. > >I found that it made more sense to check for an adjacent pawn. In that case the >en-passant capture is at least pseudo-legal. > >bruce This is what I do. I have even seen "EPD" records with an en passant target set simply because the last move was a double-move for a pawn. Even though no possible EP capture was possible (this used to break my code, in fact, but now I screen this out as I set up the position).
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.