I recently had a chance to look at the Nimzo 8 engine from Chessbase. For those that are not aware, Chessbase supports a modular chess engine architecture for all their software. For instance, you buy Fritz, and you get the Fritz GUI and playing engine. But you can also get other optional engines that work under the Fritz/Chessbase GUI as well. Nimzo 8 is one of these. You should note that Nimzo can function both as an engine within the Chessbase GUI, and as a stand-alone playing program.
The Nimzo engine was written by Dr. Chrilly Donninger, and has been around for some years now. At times, it has received significant attention from computer chess enthusiasts. For the moment, it has receded into the background a bit, but it is still an extremely strong engine nevertheless. In fact, Chessbase maintains that it is stronger than Fritz 6 at blitz time controls.
You can think of these different Chessbase engines as having their own personalities. So each engine will see moves, and play a bit differently from the others. Those that conduct game analysis have usually developed a preference for using different engines, depending on the position that they are looking at.
Nimzo has two technical features that set it apart from the competition. First off, it stores a significant amount of tablebase data in RAM. Ordinarily, an engine will have to go out to a CDROM or hard drive to access this data whenever it needs it. This slows down the move search that the engine conducts, because access to these mass storage devices is comparatively slow (as opposed to RAM). So the upshot is that you should see some small increase in playing strength, all other things being equal. One logical question to ask is how this is different from a disk cache. The answer is that the engine can chose which tablebase data is stored in RAM much better than a comparatively stupid disk caching routine (which knows nothing of chess).
People have called Nimzo a tactical monster, and its high NPS count and good blitz performance would lead one to that conclusion. This may be true, but I thought its play was quite solid. I've only had a chance to go through a few games with the program, but the ones I've looked at have given no indication that Nimzo has a wild tactical streak. From the viewpoint of this Patzer, it seemed as though Nimzo really knew where to put its pieces.
Nimzo is unique in that it also has its own meta-programming language. It is called Che, and it can be used to encode positional knowledge into the evaluation function of the engine. If you've considered writing a chess engine of your own, but have not wanted to write things like a search algorithm, and tablebase access code, then take a look at Che. The only problem is that you'll need to bone up on your Austrian - that's the language that the Che documentation is written in (English speakers are out of luck).
Nimzo can also play blindfolded chess against those of you that are man/woman enough to take it on. Needless to say, I did not use this feature that often ;-). However, for those that do want it, you can use this feature in conjunction with the sparring or friend modes, so that you can play handicap games against the computer.
One characteristic I have noticed among the various chess engines is that they prefer open positions over closed ones. However, I did not notice this same propensity with Nimzo 8, which came as a great shock to me. I have played a number of games against this engine using the handicap modes of the Fritz GUI, and it seems as though Nimzo is quite content to play closed positions. Since the main reason one buys different engines is because of differences in style, it's good to see that Nimzo delivers in this area.
I found that Nimzo makes a unique opponent in friend mode. I played several games and noticed that in the games that I won, each ended up with me gradually accruing a positional advantage. This is in sharp contrast to Fritz, in which the game is usually resolved by a tactical blow of some sort. Another interesting difference I noticed was that Nimzo plays a bit more naturally in the handicap modes. For instance, many of you have probably noticed that Fritz tends to leave its king out in the middle of the board when in friend mode - and longer than most humans would. Nimzo tends to castle at the appropriate time, but then make small positional errors, by means of slightly inferior exchanges, or passive placement of its pieces. This gave the resulting games a vastly different character from most other games that I normally play against the computer.
I did notice one bug in this program. Specifically, Nimzo will lose on time when playing games using the sparring setting. However, Chessbase is looking into this, and it will be fixed in an upcoming patch.
Conclusion
If you don't already have another engine for Chessbase or Fritz, and you are looking for another one, then this is the one I would consider. Not only is it a good analysis engine, but it is also a good playing partner as well (especially in Friend and ELO handicapping modes).
Copy Protection
CD-based refueling. At intervals, the user will be prompted to insert the CD.
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