General features

Rebel 9 is a DOS-based program, and it also runs under Windows 3.1 and Windows 95. Windows NT and OS/2 are not supported. I ran Rebel 9 under DOS primarily, and also briefly under Windows 3.1, without any problems. I was able to run it under OS/2 Warp 4, as long as I didn't allow it to run in background mode. Previous versions of Rebel have given me problems running under OS/2, and so I was pleasantly surprised with this result. The copy-protection system is transparent to the user once the program has been installed.

The program is mainly menu-driven, although there are some shortcut icons available on the screen. Keyboard entry is supported but I believe a mouse is essential for ease of use. The layout is clear and straightforward, and the program can be used without much reference to the manual. The complete manual is available on-line with context-sensitive help if required. The help system is a new feature that is very useful for quickly consulting the details of less-used features. A text version of the manual is included on the CD-ROM, but there is no printed manual. The colours of the menus and board can be changed, as can the piece sets. However, I haven't bothered with changing any of these as I'm happy with the default settings.

Strength

This aspect is easy to review: Rebel 9 is simply too strong for most of us. Rebel 8 has caused major problems for top-class grandmasters such as Yusupov, and Rebel 9 is claimed to be even stronger. In practical terms, this means that you can enjoy a challenge from the program even when it is set at very fast time controls. For most players, there is little point in letting the program think for, say, more than ten seconds per move except in its analysis mode.

The program offers various ways to decrease its strength. One simple way is to set an ELO rating for the strength you require. Alternatively, you can specify a strength in the range "novice" to "strong". For amusement, you can ask Rebel to vary its "energy level" during the game. Your task is to beat it before it gets too strong. The program includes the Rebel 7, Rebel 8 and Rebel Decade engines for extra strength and style variety. In addition, it is possible to play one engine against another.

Playing levels and styles

Rebel 9 offers the usual playing levels including fixed time, blitz and tournament levels. It also offers handicap levels where the user gets more time than the program. Alternatively, you can specify a maximum depth of search for the program. However, time increments are not included. Other options include a blindfold mode and the ability to play four games against Rebel simultaneously if you're feeling particularly masochistic.

The program's style can be varied within five levels ranging from "aggressive" to "defensive". Rebel is noted for its human-like play, and generally favours knowledge over search speed. The program has an autoplay feature for computer-computer games, which is useful to see how to play any given position. Finally, Rebel includes several options for displaying its search information including a very extensive "war room" option that I normally prefer.

Opening books

Rebel includes a large opening book, and numerous specialized books are available on the bonus CD-ROM or the web site. The opening books are editable from within Rebel. Three new and useful features of the opening book are noteworthy. Firstly, Rebel can analyse an opening book and store its evaluations. Secondly, it is possible to generate an opening book from a database. Using this option, it is easy to generate an opening book for your favourite opening and then use it to play against Rebel. Finally, Rebel now includes a book-learning option to make it stronger in the opening over time.

Analysis options

The analysis options in Rebel are excellent. As a first step, Rebel can be used to offer continuous analysis as you play through a game. The search can be refined by specifying moves to be either included or excluded, leading to a considerable speedup of the search. Rebel's game analysis option is simple and elegant. The program reports on the score and principal variation for both the move played and the move it considers best. Moreover, it provides analysis for every move played. The user only needs to specify the time to spent per move and which side (white or black, or both) to analyse. The complete analysis is stored as text comments within the game, and it can also be exported to a text file. New in Rebel 9 is the ability to analyse several games from a database in one step. Rebel can also analyse problem sets including those stored in EPD format.

Database features

The database features have been considerably extended in Rebel 9. The program now supports PGN files directly without requiring an initial conversion to its own format. Conversions between PGN and EPD formats and Rebel's format are in-built. Rebel can also detect and delete double games from a database. The database window has been extensively improved in Rebel 9, and offers many more features. Of particular interest is the game overview option that includes a facility for Rebel to evaluate a position from a game directly.

The search options have also been extended. The new options allow the user to search a database for moves, position, material or material pattern. The last two are particularly useful. The material option can be used to search for particular piece distributions, for example, two pawns versus one pawn. The material pattern option can be used to search for features such as isolated pawns, or particular pawn chains. Thus, with the new features, Rebel offers a very useful set of database facilities. The one major feature that I miss is the ability to store variations within the game.

Bonus CD-ROM

The new version of Rebel includes an excellent bonus CD-ROM. Some of the software on the CD-ROM is also available on the web site. It contains numerous databases including a main database of 107,000 games, historical games, games of famous players, computer games and problems. Out of interest, I combined all the databases (excluding the computer games and problems), and then used Rebel to delete doubles. The net result was a database of just over 148,000 games, which provides a solid base for study and research.

Also included are numerous opening books on specific openings and player repertoires to augment Rebel's main book. As there are around 56 Mb of these, they should be more than enough for most users.

In addition, the CD-ROM contains several database utilities. These include facilities to convert ChessBase and NicBase databases to Rebel's format, and facilities to manipulate Rebel databases. Finally, the CD-ROM includes some public domain and shareware items, such as a program for printing diagrams from EPD files.

Conclusion

Rebel 9 is a substantial upgrade of Rebel 8 in terms of strength and features. The program is easy to use and has a clean and visually-pleasing display. The combination of a very strong program and the bonus CD-ROM is an excellent choice for all players, and it is highly recommended.