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Wednesday, July 22, 2015

A Double Bishop Sacrifice That Failed

      In the previous game we saw a classic example of the double B sacrifice and learned what it took to make it work. Remember, these are the conditions we are looking for:

1) One Rook must be immediately available

2) The victims pieces must be unable to support the defense

3) The K cannot escape via the f-files

4) Refusal of the second B sacrifice must have serious disadvantages

5) Material at the end of the combination must be favorable to the side making the sacrifices.

      In this game it didn't quite work for Joel Benjamin. I think the reason why it didn't was because he decided to check the black K with his R on the g-file instead of the h-file. This resulted in black being able to exchange his Q for the R on g3 which blocked Benjamin's other R from being quickly brought into play long the third rank which was, after ...Qxg3, obstructed by a Pawn.

     That said, it appears from the Shootouts that even had he played to deliver the R-check on the h-file, then point 5 comes into play. The material was, theoretically, favorable to him, but the balance was so delicate that the remainder of the game wold have been very difficult to play correctly.

     Note: In several instances I used the Fritz Shootout analysis mode, so perhaps for those that are unfamiliar with this, I should briefly explain how it works. Starting from any position it is a way to get the engine to play against itself.

     You can play the games using either blitz or long time controls or by using a third method, fixed depth which is the one I used. You set the number of ply the engine is to look ahead; I used 11 ply (5.5 moves) and the engine will then calculate moves out to 11 ply search depth, then make that move. Then it will calculate a reply for the other side to 11 ply and make the move.

     There is also a second ply setting; I used 19 ply (9.5 moves). What this means is in the first game, moves will be made after a 7-ply search. In the second game the engine will move after a 9-ply search, and so on until it finally makes its move after a 19-ply search. Thus a series of five games were played starting from the position with each successive game using a deeper search. When using this function even numbered plies are skipped because some older engines exhibit a form of tactical blindness at searches which are cut off after an even number of plies.

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