Author: Heiner Marxen
Date: 12:47:55 02/05/01
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On February 05, 2001 at 15:12:53, Alvaro Jose Povoa Cardoso wrote: >On February 05, 2001 at 04:38:40, Dan Newman wrote: > >>On February 04, 2001 at 17:08:07, Alvaro Jose Povoa Cardoso wrote: >> >>>I think I found the big problem with my program: >>>I don't store captures in the hashtable, so it is impossible to retrieve a long >>>PV from it (life can be cruel). >>>I do that because captures can be a real pain in the neck to store. >>>A king (dama in the portuguese version of checkers) can make multiple captures >>>(6-9 max). >>>A normal move can be something like '30-16', but how do I store a capture like >>>'3x17x26x19x32' in the hash table? >>>Can someone give me an hint? >>> >>>Thank you >>>Alvaro Cardoso >> >>Assuming captures are made only by jumping diagonally (like in checkers in >>the US), then you only have 4 different directions that you capture in: >>NE, NW, SE, and SW. That means you can encode a capture sequence as a >>series of 2-bit codes: NE=00, NW=01, SE=10, SW=11. With 9 max captures >>this takes 18 bits. You also need a 4 bit count of the captures so you >>know where the end of the sequence is. Total for the capture sequence: >>22 bits. >> >>-Dan. > > >Yes, but in the portuguese version of checkers the king (dama) can jump over a >distante enemy piece, not just over its adjacents ones. Also, after the jump we >can 'land' our king in any free square along a given diagonal, not just the one >adjacent to the enemy pieces (like men pieces do). >Also in normal moves, the king can move to any free square along the diagonals >(like bishops in chess). >This makes the king endings very complex, with a very high branching factor. >So I need to store the captured square, the 'landing' (jumped to) square, and >the captured piece for a single capture. If I have a multiple capture then that >is a lot of info isn't it? > >Alvaro Cardoso The most compact way I can think of to store a legal move is: generate a list of legal moves in a canonical (fixed) order, and store the index of the move in the list. That index trick can be done for partial lists, also. So you may store some fixed parts of the move, like start square and landing square, and augment this with the index in the list of all legal moves that share these. Maybe along this line you find a suitable mix for your program. Heiner
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