Author: Dieter Buerssner
Date: 16:02:03 03/24/04
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On March 23, 2004 at 18:25:54, Anson T J wrote: >A game begins with 1.e4 and ends in the fifth move with knight takes rook mate. >Reconstruct the game. > >[d]rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1 The problem has exactly 2 solutions (one is a simple transposition of the other). I already indicated the second solution (besides the one, that was mentioned in other followups) in another post. I also indicated, how I came to the conclusion (with brute force search). I was not 100% sure, whether another first move of black than Nf6 could yield in another transposition (I was pretty sure, from thinking myself about it). So, additionally to the experiments I mentioned in my other followup, I also did a perft(9), but disallowing Nf6 this time (used a hash table for it). No other solutions were found. Because I already did a "perft(8)" after Nf6 without hash tables (with an algorithm, that will find all transpositions), there cannot be another solution. >Major kudos if you solve it yourself! Not really myself. Brain time: < 1/2 hour (rather easy when you intend to use a fast tool for the brute force part), CPU time: ~3 hours to come to the conclusion, perhaps another 2 hours wasted CPU time. Coding time: 20 minutes (really small changes to already existing perft code). If anybody finds another solution, I will give a crate of beer (or a nice bottle of wine, or something similar) to the first one. It would mean a horrible bug (in my thinking and/or coding). Regards, Dieter
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