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REBEL 11.0 review

by Joe Petrolito


Chess players are becoming increasingly spoilt when it comes to software. The last few years have seen enormous improvements in the Rebel line, and the latest version provides an extensive range of tools for players of all strengths. A few years ago, Rebel was provided on several floppy disks (I still have them!). Today, this is not only impractical (I don't fancy inserting several hundred floppy disks), but also unthinkable given the sheer amount of material provided.

The latest version is a significant improvement over the previous version, and consists of two separate products, namely Rebel Century 3 and Rebel Tiger II. The latter is a combination of the Chess Partner interface, two Chess Tiger engines and a Lokasoft engine. I will discuss the products separately below, although I won't discuss the basic features that no current-day program would be without, such as playing levels, display options, and so on. It's sufficient to say that there are plenty of these features, and they should satisfy most users. Extensive details on each product can be found on the Rebel web site. The package comes with a brief printed manual that describes the installation process. On-line manuals and help are also available for the individual programs.

Rebel Century 3

General features

Rebel Century 3 is a DOS-based program, although it will also run under Windows. A pure Windows-based version was mooted last year, but this has happened yet. The program is operated via an extensive menu system and on-screen shortcuts. The screen layout is completely configurable and the program comes with a set of different layouts. Users can change the layout to suit their requirements, and these new layouts can be saved.

Chess engines

The package includes five engines, namely Century 3 and the Rebel 7, 8, 9 and Decade engines. Century is the strongest engine, with the others being progressively weaker. The relative strengths of the engines can be compared by running automatic computer-computer matches.

Rebel engines have always been noted for their human-like play, and the new version is doing very well against humans, including winning the recent Debrecen tournament. Clearly, Century is too strong for all but the top players. For those of us who are not of GM strength, it's possible to weaken the engines in various ways. The way I like to do this is by setting an ELO rating for the strength.

Century's style can be varied in two ways. Firstly, the user can select one of five styles ranging from "aggressive" to "defensive". Secondly, the style of play can be changed by adjusting various search options. Some pre-configured styles for famous players are included, and others that were developed by beta-testers and end-users are on the web site. This of course leads to the question as to what the strongest settings are. It's difficult to answer this question without very extensive testing, but clearly there is a lot of scope for experimentation if you are interested.

Opening books and related tools

The chess engines are supported by a huge opening book with 2.6 million positions, and further specialized books are included on the CD. A separate chess tree is provided by the Encyclopedia of Chess (EOC), which was introduced in Rebel 10. It is basically a tree of 20 million chess positions that includes win/loss statistics for each position. Further details on EOC are given in my review.

A utility is provided for generating EOCs from any database of games. Two other trees also complement the opening book, namely a one-million Computer Analysis Project (CAP) tree from Dan Corbitt's team and a Computer Analysis Tree (CAT). The CAT concentrates on computer-computer games and analysis from computer programs. All three trees can be used to influence Century's decision-making in the opening.

Analysis options

The analysis options in Century are extensive, and include continuous analysis as you play through a game, and full analysis of individual games or set of games and problems. The analysis can be controlled by specifying moves to be either included or excluded. Statistics and ELO ratings are automatically generated for standard test sets that are provided with the program.

Database and search features

The database has been expanded to around 800,000 games, which is stored in Rebel's own format. Century also supports PGN directly, and tools are provided to convert database in Chessbase cbf format and Nicbase formats. The search options have quite extensive, and are starting to rival those provided by dedicated database programs. Searches can include header information (names, dates, etc.), positions, and material or material patterns. Options can be combined using a search mask, with any option being able to be either included or excluded.

Rebel Tiger II

General features

Rebel Tiger II is a windows-based program that acts as an interface to the Tiger chess engines and winboard-based engines, and as an interface to internet chess servers. A Century 2 engine is provided for analysis to complement the Tiger engines. As a chess-program interface, it offers a range of features that are similar to Century, so I won't discuss these. The main differences between Century and Tiger are:
  • (a) Century provides more extensive search facilities,
  • (b) Tiger can be used with the numerous (and free!) winboard engines such as Crafty, and
  • (c) the database formats are different. Tiger handles games stored in ChessPartner, cbf or PGN formats, and positions in EPD format.
The program is operated via a standard windows interface, and is very simple to use and highly configurable.

Internet console

The internet console offers a complete and comfortable link to telnet-based chess servers such as ICC and FICS. Preconfigured sessions are provided, and new or modified ones can be quickly created and saved for future use. Users can log in as a human or a computer. In computer-mode, the chess engine plays without any human intervention during the game. It's possible to have the engine automatically seek matches, and in this way the engine can be playing all the time. Games can be automatically saved to a database in both modes of operation.

Tiger engines

Two versions of Tiger are included, namely the standard Tiger 13, and the new Tiger Gambit. Tiger is a very strong engine, and a previous version topped the SSDF list. The latest versions are also performing very well, with Gambit winning the recent computer Dutch Open. Gambit caused a lot of interest amongst the beta-testers, and I must admit I spend most of my time testing this version of Tiger.

Gambit has an exceptionally aggressive style that makes it a pleasure to watch its games. It loves to conduct a mating attack whenever possible, and this often results in speculative play. This style of play is very difficult for humans to counteract, as Gambit's numerous internet opponents quickly found out. So, although the standard version of Tiger is probably slightly stronger, the Gambit version is more fun. Take your pick!


Rebel 11 offers a fine collection of chess software at a great price. The different programs complement each other nicely, and cover many of the things chess software is used for. Given this, it is very easy for me to highly recommend it.