Author: Robert Hyatt
Date: 17:08:27 01/24/99
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On January 24, 1999 at 11:11:55, Hugh Cumper wrote: >This may be very simple matter to the old pros. When I first wrote a chess >program I created a stack of boards for lookahead and copied the current board >each time I wanted to look further ahead, discarding it again to go back up. I >suppose I did that because I started writing programs for games like Kalah where >the board is small and moves are relatively epensive to take back. Recently I >have seen programs the have one board and store unmake move information in >addition to move information so the move can be retracted. I am trying to think >which is more efficient but I can't decide. Has anyone worked this out >theoretically or practically? If you are running on a PC, there is no comparison. the copy idea doesn't work, because the PC has practically no memory bandwidth to speak of, compared to what the CPU actually requires to keep it busy. Early versions of crafty did a copy-make approach so unmake just backed up the pointer and that was it. I went to the full make/unmake and picked up a lot of speed, once everything was cleaned up.
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