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" checkmate puzzles consist of "realistic" Chess positions 
in chess "epd" notation. Each puzzle has a forced checkmate in 
2 to 8 moves. These puzzles are intended for human players who 
want to improve their chess tactics. 

The object of a checkmate puzzle is to find the fastest (shortest)
path to checkmate.

The "40H" checkmate puzzles are organized into 14 basic files:

mate-b2.epd, mate-b3.epd, mate-b4.epd, mate-b5.epd. mate-b6.epd, 
mate-b7.epd, mate-b8.epd
  
mate-w2.epd, mate-w3.epd, mate-w4.epd, mate-w5.epd. mate-w6.epd, 
mate-w7.epd, mate-w8.epd
 
"mate-w3.epd", for example, contains positions where there is a 
forced shortest checkmate for "White" in "3" moves.

There are 4 additional files: mate-all.epd, mate-all-w.epd, 
mate-all-b.epd, and mate-all.pgn.

The checkmating side does not have an overwhelming material 
advantage. In 75% of the puzzles, the checkmating side does not 
have ANY material advantage. In the other 25%, the material 
advantage is limited to a maximum of 2-pawns or equivalent. 

There are 28,000+ chess puzzles in this collection, split equally 
between White to move and Black to move. Each puzzle has a 
flipped version in the other color that is logically equivalent. 
For example, each puzzle in mate-w4.epd has an equivalent puzzle 
in mate-b4.epd, and vice versa.

Each puzzle "epd" record has a "bm", "pv", "ce" and "id" opcode.

Each of the puzzles in this collection has a unique first best 
move. That best move ("bm" opcode) leads to the shortest (fastest) 
checkmate. Solutions having more than one best first move have 
been excluded. 

The predicted variation ("pv" opcode) lists one shortest checkmate 
path starting with the "best (first) move". There can be more than 
one "shortest" path with the same number of moves and the same
first move.

The centipawn evaluation ("ce" opcode) indicates the numerical 
advantage/disadvantage of the position in centipawn units from the
viewpoint of White. Due to the impending checkmate, "ce" has been 
converted to an alternative form that shows the minimum number of 
moves for a forced checkmate. For example, "ce +M4;" means White 
has a 4 move "shortest" path to checkmate. A negative value, such 
as "ce -M3;" indicates Black has a 3 move "shortest" path.

The "id" opcode shows the "id" number created by the editor. 
Each record has a flipped version with the same "id" number. 

A "PGN Viewer" is recommended for visual purposes.

There are no duplicate positions.

There are no duplicate predicted values ("pv opcode").

No missing Castling permissions.

No faux (or false) "en passant" target squares.

"bm" and "pv" output is in LAN (long algebraic notation).

No "en passant" notations (which are not required) in the "pv"
opcode.

  https://en.wikipedia.org/wiki/Checkmate_pattern
  
The positions used in this collection were found in the Public 
Domain, and then edited. 
  
Thw software used for this project consisted of "ChestUCI v5.2" 
by Franz Huber (based on "CHEST v3.19" by Heiner Marxen), 
"Arena 3.5.1" by Martin Blume, "PGN-Extract" by David Barnes, 
and "40H-EPD" tools by Norman Pollock.

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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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