By the way, there is a very interesting tournament going on currently -- TCEC, unofficial computer chess championship [1]. The main intrigue of the tournament is the fight between Stockfish and Komodo. Houdini, dominating engine in the last few years, already lost any chances to go into the superfinal -- two very strong challengers, Komodo and Stockfish, in the last few months were able to eat huge advantage of Houdini. The author of Komodo, Don Dailey, is terminally ill, according to his wife he has just a few days to live, so it's possible that he will not know if his engine will win or not. It's really heartbreaking, he was very active in the chat of TCEC just a few days ago, commenting games, discussing computer chess and so on. Stockfish is an open-source engine that uses distributed testing framework, so anybody can participate in its development donating CPU time [2]. Both engines are very strong and have relatively equal strength.
[1] http://tcec.chessdom.com/ [2] http://tests.stockfishchess.org/