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

"40H-EPD-databases" is copyright (c) 2014-26. All rights reserved.

These databases are freeware. They contain chess positions from
the Public Domain and the "epd" records were edited by Norman 
Pollock.

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

The object of a checkmate puzzle is to deliver the checkmate
in the least possible number of moves. 

"40H" checkmate puzzles consist of realistic Chess positions 
presented in "epd" notation, with a solution included in the 
opcodes. The positions are aimed at human players looking to
improve their tactical skills.

A PGN-Viewer is necessary to "see" the positions since the 
puzzles are presented in "EPD" format. 

Positions with a large material advantage (3+ pawns or 
equivalent) for the checkmating side have been excluded.

Each puzzle has a shortest forced checkmate in 2 to 8 moves.

Solutions have been checked by "ChestUCI" by Franz Huber.

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

mate-b2.epd, mate-b3.epd, mate-b4.epd, mate-b5.epd, mate-b6.epd,
mate-b7.epd, mate-b8.epd

  and

mate-w2.epd, mate-w3.epd, mate-w4.epd, mate-w5.epd. mate-w6.epd,
mate-w7.epd, mate-w8.epd
 
For example, "mate-w3.epd" contains positions where there is a 
forced shortest checkmate for "White" in "3" moves.

Each puzzle has a flipped version in the other color, with the 
same "id" number. The flipped puzzle versions are logically the
same.

There are 39,000+ chess puzzles in this collection, divided 
equally between "White to move" and "Black to move". 

The breakdown is as follows:
  mate-b2, mate-w2: 3663
  mate-b3, mate-w3: 5506
  mate-b4, mate-w4: 4604
  mate-b5, mate-w5: 2565
  mate-b6, mate-w6: 1582
  mate-b7, mate-w7: 1157
  mate-b8, mate-w8:  628
           TOTAL = 19705 per color, 39410 aggregate.

The puzzles are NOT rated and are NOT arranged by difficulty. 
They are arranged alphanumerically. 

Editing: 
1. Maximum material advantage for the checkmating side is 2 pawns 
or equivalent.
2. No multiple winning moves in the starting position. There may
be multiple paths to checkmate after the starting move.
3. NO duplicate positions. 
4. NO duplicate predicted variations (pv opcode).
5. NO false "en passant" notations.
6. Missing "Castling" permissions restored if the King/Queen and 
Rook are in a Castling position.

When using a PGN Viewer:
1. Do NOT assume "en passant" permission exists. Check the "epd" 
record.  
2. "Castling" permissions always exist if the King/Queen and Rook 
are in a Castling position.           . 
 
Opcodes:
Each puzzle "epd" record has a "bm", "pv", "ce" and "id" opcode.

Each puzzle has a unique best 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 others,
but only one is listed.

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. Examples: "ce +M4;" means White 
has a 4-move "shortest" path to deliver checkmate, "ce -M3;" means
Black has a 3-move "shortest" path to deliver checkmate.

The "id" opcode shows the "id" number created by the editor. 
Each record has a flipped version with the same "id" number in
the corresponding file of the other color. The flipped versions
with the same "id number" are logically equivalent puzzles.

A "PGN Viewer" is a necessity to "see" the "epd" positions.
  
Sources:
The positions in this collection were found in the Public Domain
and then edited into "epd" format with additional opcodes. 

Software Used:  
"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, "Chessvision.ai" by Pawel Kacprzak, 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.
 
To Report Problems or Suggestions: rc1242@yahoo.com

Norman Pollock, editor
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