United engines – which one do I need?

by ChessBase
6/24/2010 – What chess program is best suited for analysis? Rybka, Fritz, or Shredder? Is there any sense in using more than one of them? Bo Bredenhof is a correspondence chess player and experienced engine user for years. In his article at  chesscafe.com he tells us where each top programs has its strengths and where it fails to find the best move. His bottom line: united they stand strong.

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Chess Software

By Bo Bredenhof (chesscafe.com)

There are many chess software programs on the market. They commonly consist of three main parts: a graphical user interface, a database handler, and a chess "engine." The most important part for the CC player is the chess engine and its performance capabilities.

In recent years, new generations of the most widely used software are released almost annually. Presently, we have Fritz 12, Shredder 12, and Rybka 4. There are also "Deep" (i.e., multiprocessor) versions for each; these are much faster and because of that also a bit "smarter."

The Elo rating of these program are similar, but they differ in calculating speed, how good they are in different phases of the game, and how they handle different types of positions.

To be truly competitive in today's CC (top twenty percent and higher), I recommend that you use the latest versions. Though the great leaps in performance between generations are over, so you may not need to have the latest and greatest. It is often more important to learn how your present software works and how to get the most out of it.

I have used Fritz 5 and every version since, including Deep Fritz 11. I have read about other CC players who use more than one software program during their analysis. But I didn't want to make my CC life any more complicated, so I stuck with my one and only Fritz until just recently.

I became a little disappointed with Fritz when I first began playing the Najdorf Sicilian as black. In most positions, Fritz insisted on an evaluation of -0.5 or worse. It is psychologically distressing to get the feeling that you have a lousy position in many of your games; especially as black, where the margins are small. I then read an article by a very good Swedish player, Per Sörenfors, who wrote that Rybka was much better in evaluating unbalanced positions and that it was a very good complement to engines such as Fritz. So, after a while, I acquired Deep Rybka 3 and its evaluation of my Najdorf positions was much more positive; about equal. Thus, from then on, I always used Rybka in certain positions and Fritz in others.

Another weakness with Fritz is that it often underestimates the opponent's attack, and only discovers the seriousness of the situation too late. In the same way, it overestimates its own attacks and doesn't realize until too late that it fails. Fritz also has a tendency to lash out with weakening pawn moves in the early part of a game. Rybka seems to be more careful and realistic.

Yet, while Rybka works well in unbalanced positions, it sometimes suggests weakening or slow moves in balanced and closed positions. Fritz seems to be more direct and imaginative in these positions.

Another weakness with Rybka is how it handles very complex positions when there are many possibilities for exchanges or sacrifices. (Do you remember Bobby Fisher's "sac, sac and mate"?) Fritz seems to be more inventive in these positions. Rybka sometimes fails to take some interesting variations into consideration. I often trust Fritz more here.

Rybka also seems slow in the endgame, at least compared to Fritz. Still, I don't trust any software more than four plies (four half-moves) in the endgame. We'll deal with further weaknesses in future chronicles as we encounter them.

Another thing to consider is that you do not have to buy several interfaces to obtain a second opinion from a different engine. Most software allows more than one engine to run in its interface, and some have several built in engines to choose from. Crafty is often one of them. It is fast and works well in complicated positions.

Processor speed is an important factor with chess software. It is closely related to how you can work with your analysis. Fritz is a good choice for providing variations to consider after only a short analysis period. But it can go astray early, so you have to check the variations to make sure they hold up to the initial evaluation. With Rybka you have to be more patient. It calculates considerable slower than Fritz. But the variations seems to be more reliable to a greater depth. So

if you only want to enter your position in the software and do something else for an hour or more, Rybka should suit you better. If you play many games at the same time, speed is of greater importance and Fritz should be a good choice. But you have to be very active with your analysis and interact a lot with the engine. If you only play a few games and wish to deeply research selected moves, I would recommend Rybka. Or, if you are like me, a selective use of both Fritz and Rybka in different phases of the games can be the best solution.

In my experience, the longer you work on a game, the better it will be. I am not referring to depth in variations now. Say you have three alternative moves and follow the variations in many directions for an hour or more. You may get a new best line or have a certain line confirmed as the absolute best after this session. Because the program stores the best variations in hash memory, it is possible that these threads will lead to a better variation or a completely new evaluation of a former variation. This is more common in very complex or closed positions and endgames. But, again, you have to be very active in the analysis process to create these new possibilities.

Next time we will analyze a game together. Until next month: good luck with your CC play!

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