Chess Openings Book Software

OBK2PGN

OBK2PGN is a program which converts Chessmaster openings books to PGN format. This is useful if you want to use TheKing engine under some other GUI (e.g. Fritz or Arena) but still use the original opening book.

Running OBK2PGN

OBK2PGN is a Win32 program which needs to be run from a command prompt. It takes two arguments, the first is the name of the OBK file you want to convert, the second is the name of the PGN file that will be created. For example:

OBK2PGN CMX.OBK CMX.PGN

OBK2PGN will either have to be in the path or in the current directory. The above example assumes that the CMX.OBK file is also in the current directory, and the CMX.PGN file will also be created in the current directory.

It's not particularly fast - the CMX book might take about 30 - 60 minutes to convert. If everything is working OK you should get progress indications displayed every 1000 moves processed. It performs the conversion in two separate phases which take about the same amout of time each.

PGN Output

Each variation in the original OBK file is output as a separate game in the PGN file. Each move is annotated according to the book score: 3 = !!, 2 = !, 1 = , 0 = ? .

Often in a Chessmaster book it is possible to reach the same position via multiple different lines, often with different scores. This causes problems when converting to an opening book format which stores positions rather than moves. To avoid these problems, the program calculates which score is most common for each position and standardises them.

Using the PGN output in Fritz

Create a new opening book, then choose 'Import Games' from the Edit/Openings Book menu and select the PGN file created earlier. I'd suggest setting the length high (say 100) to ensure you get the whole book. There are no variations, so what you set 'Include variations' to is unimportant.

In the Book Options page I would suggest setting 'Minimum games' to 1, otherwise the tail ends of each variation will be ignored.

The move annotations don't appear to have much effect on move selection, except that the ? moves are correctly avoided completely. The main thing that determines how often each move is played is the number of games, which in this games means the number of different variations which branched off from that move. That seems to give reasonable results, since the Sicilian (for instance) has much more theory and hence variations than say the Caro-Kann.

Version History

26-Jan-2005

Altered the way annotations are assigned. Previously if the same position was reached via two or more move orders with different annotations, whichever annotation was more common was used, tie-breaks going to the worse annotation. For cmx.obk, this resulted in b5 being given a ? in the line 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5, and there were probably many other similar cases. The new version also chooses the better annotation, regardless of which is more common.

27-Jan-2005

Further refinements to annotations. Now annotations are only standardised for situations where the same move is being made from the same position. I had assumed that annotations were actually stored againt positions in Chessbase book format (.ctg) but this proved to be incorrect. Hence there is no need to force the annotations for all moves leading to the same position to be the same. Where annotations do need to be standardised, preference is now given to the line with the most variations. Tie-breaks now go to the better annotation.

Download OBK2PGN here. (60KB zipped)

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