Scid++ Files

The following PGN-formatted databases serve as a resource for the 'CQL by Example'
document suite.  Each example CQL query will match at least a handful of the
problems in one or more of the databases.

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problems.pgn.gz

A collection of orthodox direct/help/self/reflex [stale]mates quoted from various
online resources, with full solutions by Popeye v4.85. The resources include:
  -- Eduardo Sadier's direct-mate-in-two problem database
  -- Brian Stephenson's Meson CPDB
  -- Dmitri Turevski's Yet Another CPDB
The quoted resource is carried in the PGN Site tag for each composition.

All duplicate problems have been eliminated from the database, with preference
going to YACPDB. Duplicates are detected via a hash on each problem's FEN string
(see the project's composer branch), with side-by-side examination revealing
that a good many of the dups comprise anticipations (preference given most often
to the earlier dated composition), or resubmissions by the author (preference
given to a prize-winning submission and/or the reputation of the source).

Each of the Meson problems' PGN Round tags carries -- for reference -- the
corresponding Meson PID.  That PID may be employed in an online query to look
up the composition's original metadata.  (Unfortunately, the online database has
had all but the direct mates deleted, apparently due to resource constraints.)

Some of the compositions having solution trees with more than 2500 nodes have
been re-solved to include just actual play. Most of these problems are of the #[4-5]
class and may easily be re-solved to include the full solution. Use the Scid general
header search facility to find them, searching for "*Actual Play" (including the quotes)
in the black player tag.

The compressed file expands to just under 1 GB in size (nearly half a million
compositions, many with very large solution trees). Scid will import the database
in its compressed format, and grepping or otherwise examining the PGN metadata may
be accomplished via the various 'Z' tools (zcat, zless...), so the file need never
be decompressed for typical usage.

Update 2020-12-07: break out compositions with twins to a separate database.

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direct4d.pgn.gz

A slice of problems.pgn including compositions having stipulations of #3-5.

By default, the solving engine will cull any try having more than one defense.
That is normally the desired behavior, but for some themes (especially promotion-
oriented themes, e.g., the Holst) the multi-defense try may be thematic and the
solution tree should include these lines for query purposes.

This database has been solved with Popeye options
    'Variation Try SetPlay NoShortVariations Defence 4'
which is probably the sweet spot in terms of defenses allowed, though the rare
composition may legitimately provide for a thematic try with more than 4 defenses.
Call it a compromise.

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twins.pgn.gz

Separated from problems.pgn for special processing, comprising 28,000+ compositions
with twins. All twin specifications have been brought up to Popeye-conformant syntax.

Update 2020-12-16:

The database has been expanded to include twin series production with full solutions
by Popeye v4.85.

A series of twins for any given composition will share an ordered sequence of
PGN Round numbers having a common base modulus N which is unique across the database,
such that a database sorted by the Round tag will be reliably ordered.

Update 2021-01-10:

Add a twin count to the BlackElo PGN tag.

Update 2021-03-13:

Add a couple of series for a modified Igman theme and an additional cyclic Monkey theme.

Update 2021-08-08:

Correct some flips along the wrong diagonal.

Update 2021-08-09:

Add a PGN "SeqNum" tag for series completion.

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babson.pgn.gz

A direct-mate-in-four Babson database with partial solutions.
Virtual play and set play are omitted to reduce game tree size.

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hoffmann.pgn.gz

A direct-mate Babson database with partial solutions.
Virtual play and set play are omitted to reduce game tree size.

The problems have been programmatically generated from Peter Hoffmann's
"100 Years: Babson Task in the Orthodox Directmate" (Version: 18.04.2020).

Numerous typos and errors in the position setup strings have been corrected such
that all problems in the database agree with the diagrams (and solutions with keys)
in the paper, rather than with the corresponding setup strings.

A few problems have been omitted because they could not be [legally] translated
to a FEN string.



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libcql.tar.gz

We also have planned a number of CQL libraries of functionality which are in
use across the document suite. Currently, the following libraries are in use:
  -- libfen.cql   translates between FEN strings and a set of bitboards
  -- libxfm.cql   a suite of transform utilities for cross-twin queries
Simply unpack the tarfile in a convenient place and add an "include" directive
to the CQL header.

Update 2023-10-15:

Add a third library to libcql which will expand over time:
  -- libhlp.cql   a collection of helper functions