Author: Andreas Guettinger
Date: 13:05:31 01/02/03
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On January 02, 2003 at 15:51:30, Russell Reagan wrote: >[D]r3k2r/8/8/8/8/8/8/1R2K2R b Kkq - 0 1 > >In the above position, I calculate perft 3: > >> perft 3 >26 0 >583 0 >14251 0.032 >total time: 0.032 > >Other engines say that perft 3 is 14252, so I assume that I am wrong here and I >went looking for the position where the error is. I wrote a function to tell me >preft (n-1) for each of the legal moves so I can tell which branch the error is >in, and I continue to narrow it down until I find the offending position. This >has worked well so far, but now I'm getting this: > >> dperft 3 >h8h1 87 87 >a8a1 356 443 >a8a2 544 987 >a8a3 631 1618 >a8a4 631 2249 >a8a5 631 2880 >a8a6 631 3511 >a8a7 631 4142 >a8b8 524 4666 >a8c8 559 5225 >a8d8 488 5713 >h8h2 428 6141 >h8h3 547 6688 >h8h4 575 7263 >h8h5 602 7865 >h8h6 628 8493 >h8h7 650 9143 >h8f8 490 9633 >h8g8 560 10193 >e8d7 720 10913 >e8e7 742 11655 >e8f7 692 12347 >e8d8 510 12857 >e8f8 490 13347 >e8g8 474 13821 >e8c8 431 14252 > >This function reports perft n-1 for each move, and keeps a running total on the >right. The last number in the right column is, to my suprise, 14252, which is >the correct perft 3. > >So when I calculate perft 3, it is incorrect, but when I ask it to give me a >breakdown of perft 2 for each move, the sum (which should be the same as what I >am getting for perft 3) is suddenly correct. > >Any idea what this could mean? I'm stumped... Strange. Do you have a nodes--; somewhere when you iterate back out of your search function? But this would have nothing to do with castling... regards Andy
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