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 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:

"40H" checkmate puzzles consist of Chess positions in "epd" notation.
Each puzzle has a forced checkmate in 2 to 8 moves. 

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 5 additional files: mate-all.epd, mate-all-w.epd, 
mate-all-b.epd, mate-all-sort.epd and mate-all.pgn.

There are 32,000+ chess puzzles in this collection, split equally 
between "White to move" and "Black to move". The puzzles are NOT
rated by difficulty. 

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

file                # puzzles
mate-b2, mate-w2      2,750
mate-b3, mate-w3      4,318
mate-b4, mate-w4      3,519
mate-b5, mate-w5      2,266
mate-b6, mate-w6      1,503
mate-b7, mate-w7      1,100
mate-b8, mate-w8        594

Filters: 
1. Maximum material advantage for the checkmating side is 2 pawns 
or equivalent.
2. No multiple winning moves in the starting position. 
3. Kings do not pass each other vertically.
4. NO duplicate positions. 
5. NO duplicate predicted variations (pv opcode).
6. NO false "en passant" notations.

When using a PGN Viewer:
1. Do NOT assume an "en passant" permission exists. Check "epd".             . 
2. Castling permissions exist if pieces are in 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 they are not 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 checkmate, "ce -M3;" means Black
has a 3 move "shortest" path to 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.

Miscellaneous:
A "PGN Viewer" is recommended for visual purposes.
"bm" and "pv" moves are in LAN (long algebraic notation).
Users should be familiar with common checkmate patterns.
  https://en.wikipedia.org/wiki/Checkmate_pattern
  
Sources:
The positions used in this collection were found in the Public 
Domain, and then edited. 

Software:  
Software used 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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