Author: Peter Fendrich
Date: 01:37:09 01/08/03
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On January 08, 2003 at 00:01:19, Russell Reagan wrote: >On January 07, 2003 at 23:49:20, Joel wrote: > >>Could someone please explain what Perft is, and perhaps what it is useful for? > >Perft is a function that computes the number of nodes visited to a given depth. >Another way of thinking of this is the number of games, or paths, that exist to >a given depth. So from the opening position, perft 1 is 20, since there are 20 >legal moves at depth 1. Perft 2 is 400 (which is 20 x 20). Basically you are >just counting positions to a given depth. > >What this is useful for is determining if your move generation, your make move, >and your unmake move functions are working correctly. For example, if your move >generation function doesn't generate castling moves correctly, you will get an >incorrect perft result. Or if your program didn't generate double pawn moves >(like e2e4) then it would calculate perft 1 incorrectly for the initial >position, and you could see which moves it doesn't generate correctly, and you >could fix the problem. Also it tests your make/unmake functions, because if (for >example) you forgot to replace a captured piece in your unmake move function, >then you would get incorrect perft results, and you could find that bug and fix >it. > >Basically it's a way to see if your move generator and make/unmake have any bugs >in them. You should know by now...-:) Did you find out what your perft problem was? /Peter
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