readme for "40H-EPD-databases", edited by Norman Pollock

"40H-EPD-databases" is copyright (c) 2014-24. All rights reserved.

These databases are freeware. They contain chess positions 
available in the Public Domain on the Internet or elsewhere, and 
were edited by Norman Pollock.

No warranty, expressed or implied, is made that the information 
provided in "readme-epd-db.txt" or in the positions, is accurate. 

No warranty, expressed or implied, is made as to the worthiness 
of these files for computer or chess usage. 

The user bears full responsibility for any consequences from 
the use or misuse of these files. The editor is not responsible 
for any damages or losses of any kind.

These databases can be freely distributed provided they are 
distributed "as is". The editor is not responsible for any 
changes made by others.

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Overview:

"40H-EPD-databases" contain checkmate puzzles from 2 to 7 moves. 

They are organized into 12 files:

mate-b2.epd, mate-b3.epd, mate-b4.epd, mate-b5.epd. mate-b6.epd, 
mate-b7.epd
  
mate-w2.epd, mate-w3.epd, mate-w4.epd, mate-w5.epd. mate-w6.epd, 
mate-w7.epd
 
"mate-wX.epd" files contain forced mates for "White" in "X" moves.

"mate-bX.epd" files contain forced mates for "Black" in "X" moves. 

For example, "mate-b3.epd" contains forced mates for "Black" in "3"
moves.

There are 5 extra files: mate-all.epd (all positions), mate-all-w.epd
(all positions with White to move), mate-all-b (all positions with
Black to move), mate-all-sort.epd (all positions sorted), and 
mate-all.pgn (pgn games based on FEN tags).

Positions are from the Public Domain and then edited.

The object of each puzzle is to find the single shortest checkmate 
path. Each position has only one shortest checkmate path. The 
solution path is listed in the "pv" (predicted variation) opcode.

A material advantage of the attacking side, if it exists, is 
limited to a maximum of +2 pawns or equivalent (e.g. rook vs knight 
or bishop).

There are no false "en passant" target squares. False "en passant"
squares (no opponent piece in position to capture) have been 
removed.

There are no duplicate positions.

Each "epd" record (puzzle) has a "bm" opcode ("best move"),
a "ce" opcode ("centipawn evaluation" which has been converted
to "distance to mate"), a "pv" opcode ("predicted variation") 
and an "id" opcode. 

The "bm" opcode shows the unique first move for the single 
checkmate path.

The "ce" opcode is evaluated from the viewpoint of White, as 
required by "PGN Standards". This opcode indicates the numerical 
advantage/disadvantage of the position in centipawn units. Because
of the impending checkmate, it is converted to the minimum number 
of moves to a forced checkmate. For example, "ce +M4;" means White 
has a 4 move path to checkmate. A negative value, such as "ce -M3;"
indicates Black has a 3 move path to checkmate.

The "pv" (predicted variation) opcode shows the single shortest
checkmate path. There are no duplicate "pv" opcodes.

The "id" opcode shows the "id" number supplied by the editor. 
The "id" opcode connects each position with its flipped version.

Each record has a flipped version with the same "id" number. 
Flipped versions have the colors reversed and the pieces flipped 
in a vertical reflection over the imaginary horizontal line 
between ranks "4" and "5". The color to move, "castling" rights", 
and "en passant" rights are also reversed. The two versions are 
logically equivalent.

Classical checkmating patterns can be found at:

  https://en.wikipedia.org/wiki/Checkmate_pattern
  
Thw software used was "ChestUCI v5.2" by Franz Huber (based on 
"CHEST v3.19" by Heiner Marxen), "Arena 3.5.1" by Martin Blume, 
"40H-EPD" tools by Norman Pollock, and "PGN-Extract" by David 
Barnes.

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"40H-EPD-databases" has 2 download sites:

  40hchess.epizy.com

  nk-qy.info/40h  (Thanks to Frank Quisinsky)

Please bookmark.
 
contact: rc1242(at)yahoo(dot)com

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