EPD files

An EPD (extended position description) file is a collection of positions, where each position has some associated text. Like PGN, it is a common standard for chess information.

An EPD file has a number of defined opcodes (fields) which are stored separated by semicolons (;) in the file but are shown on separate lines in a ChessDB EPD window to make editing easier. A semicolon within an EPD field is stored as "\s" by ChessDB to distinguish it from an end-of-field marker. Each position and its associated opcodes are stored on one single line in the EPD file.

Standard EPD opcodes include:

• acd Analysis count: depth searched.
• acn Analysis count: number of nodes searched.
• acs Analysis count: search time in seconds.
• bm Best moves: move(s) judged best for some reason.
• ce Centipawn evaluation: evaluation in hundredths of a pawn from the perspective of the side to move -- note this differs from the Analysis window which shows evaluations in pawns from Whites perspective.
• cX Comment (where X is a digit, 0-9).
• eco ECO system opening code.
• id Unique Identification for this position.
• nic New In Chess system opening code.
• pm Predicted move: the first move of the PV.
• pv Predicted variation: the line of best play.

EPD files have a number of uses: ChessDB uses an EPD file to classify games according to the Encyclopedia of Chess Openings (ECO) system, and you can create an EPD file for your opening repertoire, adding comments for positions you regularly reach in games.

You can create a new EPD file or open an existing one, from the [New] and [Open] commands of the [File] menu. At most four EPD files can be open at any time.

EPD windows

For each open EPD file, you will see a window which shows the text for the current position. You do not have to press the Store button to store any changes you make to a positions text; the text will be stored whenever you move to a different position in the game.

Navigating EPD files

To browse through the positions in a EPD file, use the [Next position] and [Previous position] commands from the EPD window [Tools] menu, or use the shortcut keys Ctrl+DownArrow and Ctrl+UpArrow. These commands move to the next/previous position in the file, clearing the current game and setting its start position.

Stripping out EPD fields

EPD files you find on the Internet may contain fields that do not interest you, and they can waste a lot of space in the file. For example, an EPD file of computer evaluations might have ce, acd, acn, pm, pv and id fields but you may only need the ce and pv fields.

You can strip out an EPD opcode from all positions in the EPD file using the [Strip out EPD field] from the EPD window [Tools] menu.

The EPD window status bar

The status bar of each EPD window shows:

• - the file status (-- means unchanged, XX means changed, and %% means read-only);
• - the file name;
• - the number of positions in the file;
• - legal moves from the current position reach another position in this EPD file.