Stockfish 6 Tactical Results - Important

     I came across an interesting post the other day on the Rybka Forum where a poster said that on his tactical test Stockfish 6 scored 81 percent with an average solve time of 13.92 seconds while Komodo 8 scored 76 percent with 21.48 seconds. Stockfish 6 was very fast on some hard positions but it also completely missed some easy wins. If you're looking for a tactical genius then he recommends either Houdini 3 or 4 on tactical mode which scored around 90% with solve times averaging around 10 seconds. He observed that Stockfish 6 sees moves quickly but in his opinion these days the effort is on verifying that a move is good rather than seeking out the best move.

White to move

     The poster wrote that in the above position Stockfish 6 failed to find the best move after 18 hours of searching while Houdini 4 found it after a few seconds! I plugged the position into my program and after about 3 minutes Stockfish 6 (using 2 cores) wanted to play 1.Kf1, evaluating the position at 0.00. Komodo 8 liked 1.Rf8 with the same evaluation.
     I have Houdini 2 and it took only a few seconds to find the correct 1.Bf8+, evaluated at 4.39.  Houdini 1.5 also found 1.Bf8+ in a few seconds! I was curious to see what happened when I showed Stockfish 6 the correct 1.Bf8+. I did not give it a lot of time but just scrolled through the moves and it did not realize white was winning until I got to move 5 which was the same for Komodo 8. Further discussion can be found on the Rybka Forum HERE.
     I checked several other engines (Black Mamba, Critter 1.6, Fritz 11, Gull 3 and Deep Rybka 4). Curiously, after about 20 seconds Critter 1.6 preferred 1.Bf8+ but evaluated the position at 0.00. But when I actually made the move, the evaluation immediately jumped to 5.00! The other engines did not find 1.Bf8+ and even after making the move on the board they didn't change the 0.00 evaluation.
     This is an important lesson! If you are using Stockfish or Komodo to analyze, you should have Houdini running as a second engine!