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

"40H-EPD-databases" is copyright (c) 2014-25. 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. 

The object of each checkmate puzzle is to find checkmate for the 
side to move in the shortest possible number of moves. 

The checkmate puzzles are organized into 12 basic 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
 
For example, "mate-b3.epd" contains positions with a forced mate 
for "Black" in "3" moves, where "3" is the shortest possible number
of 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 using FEN tags).

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).

Faux (or false) "en passant" squares have been removed.

There are no duplicate positions.

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

"bm" and "pv" output is in LAN (long algebraic notation) in lieu 
of the more common SAN (short algebraic notation) for the purpose
of clarity.

Each of the puzzles in this collection has just one best move. 
That best move ("bm" opcode) leads to the shortest (fastest) 
checkmate. Puzzles with more than one best move have been excluded. 

The predicted variation ("pv" opcode) lists a shortest checkmate 
path starting with the "best (first) move". There might be more 
than one shortest path, but only one is listed. 

The centipawn evaluation ("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 for 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 "id" opcode shows the "id" number provided by the editor. 
Each record has a flipped version with the same "id" number. 
The two versions are logically equivalent. The flipped versions 
of positions in "mate-wX.epd" are in "mate-bX.epd", and vice 
versa.

Users should be familiar with classical checkmating patterns. 
Many can be found at:

  https://en.wikipedia.org/wiki/Checkmate_pattern
  
The positions used in this collection are in the Public Domain. 
They were then edited. 
  
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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