=encoding utf8

=head1 NAME

pds_48.db - larger database with planar difference set samples

=head1 VERSION

This is version 1.1 of the database, created on September 17, 2019.

=head1 DESCRIPTION

This file is a slightly larger sample database only used for testing.

It contains 48 cyclic planar difference sets with orders ranging from
2 to 149.  The sets are generated from Conway polynomials.

The database does not contain planar difference set space data introduced
with version 2.0 so we can test backwards compatibility.

=head1 FILE FORMAT

SQLite 3.x database.

=head1 SCHEMA

  CREATE TABLE difference_set (
    order_      integer NOT NULL PRIMARY KEY,
    base        integer NOT NULL,
    exponent    integer NOT NULL,
    modulus     integer NOT NULL,
    n_planes    integer NOT NULL,
    deltas      blob    NOT NULL
  );

=head1 DATA REPRESENTATION

If I<D = { d_1, d_2, ..., d_k } (mod m)> is a canonical cyclic
planar difference set of order I<k - 1> with I<d_1 E<8801> 0> and
I<d_2 E<8801> 1 (mod m)>, I<deltas> is a sequence of I<k - 2> numeric
values packed in C<'w*'> format, calculated as differences of consecutive
residue values of I<D> starting with I<d_3 - d_2>.  The difference of
the smallest two values in a canonical set is always 1 and thus not
important to store.

=head1 PROVIDER

Martin Becker, E<lt>becker-cpan-mp I<at> cozap.comE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2019-2021 by Martin Becker, Blaubeuren.

This library is free software; you can distribute it and/or modify it
under the terms of the Artistic License 2.0 (see the LICENSE file).

The contents of this database are mathematically defined entities.
The provider believes mathematical constants not to be proprietary or
subject to copyright legislation, although the software used to calculate
them and the accompanying documentation certainly are.

=cut
