Ubuntu Manpage: fairymax - xboard-compatible chess and chess-variant engine 'Fairy-Max'

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NAME

       fairymax - xboard-compatible chess and chess-variant engine 'Fairy-Max'

SYNOPSIS

       fairymax [hashSize] [iniFile]

       shamax [hashSize] [iniFile]

       maxqi [hashSize] [iniFile]

DESCRIPTION

fairymax is a program that plays chess and chess variants. It uses the xboard/winboard chess-engine
protocol to communicate. Apart from 'regular' chess (also known as the Mad-Queen variant), it can play
Capablanca chess, gothic chess, janus chess, knightmate, cylinder chess, berolina chess, superchess,
makruk (Thai chess, and also some of its variants, Cambodian chess (Ouk), asean chess and ai-wok),
courier chess, Seirawan chess, Spartan chess, falcon chess, great shatranj, team-mate chess, charge of
the light brigade, king of the hill, bifurcator chess, Los-Alamos chess, Mexican chess, Ciccolini's
chess, grande acedrex, wildebeest chess (almost), shuffle chess without castling and chess with different
armies (all combinations of the FIDE, Clobberers, Nutters and Rookies armies). Fairy-Max can be easily
configured by the user to play other variants as well, by modifying the ini file. This ini file
describes the rules of movement of the participating pieces and the initial board setup.

Fairy-Max can also play shatranj, but in this case is not aware of the shatranj rule that a bare king
loses. So it might play sub-optimally in the late end-game. A version of Fairy-Max adapted to implement
the baring rule (and the rule that stalemate is a win) is available under the name shamax. Grande
Acedrex and Courier Chess might also have had a baring rule, so you may want to play these with shamax
instead of fairymax too.

Similarly, a version of Fairy-Max adapted to play Xiang Qi (Chinese Chess) is included in the fairymax
package as well, under the name maxqi.

fairymax is a derivative of the world's (once) smallest chess program (source-code wise), micro-Max. The
latter measures less that 2000 characters, (about 100 code lines), and has a computer rating of around
2050 on the CCRL rating list. Although this is about 1000 rating points behind the world champion,
micro-Max still makes a quite tough opponent even for club players, although it is not unbeatable.

The main difference between micro-Max and Fairy-Max is that the latter loads its move-generator tables,
which specify how the various pieces move, from an external file, so it can be easily adapted to
incorporate un-orthodox pieces. For ease of use of the artificial-intelligence, Fairy-Max is equipped
with I/O routines that allow it to run with the xboard graphical user interface.

See xboard(6) for instructions about how to use fairymax through xboard. To start up quickly, you just
need the command: xboard -fcp fairymax. Note that to be able to play the chess variants, it is
recommended to use the latest XBoard version, as some of the recently added variants will use features
not supported by older XBoard versions (in particular allowing an engine to reconfigure XBoard's ideas on
the initial setup and how the pieces move). Problems with older XBoard versions might range from only
being able to play the variant with legality testing switched off, inability to display some of the
unorthodox pieces in board sizes other than Bulky, Middling or Petite, not recognizing variants with non-
standard names, to refusing even names that by now are standard XBoard variants.

For some variants even the name is unknown to XBoard, and they are all grouped under the catchall name
'fairy'. Which variant is played by Fairy-Max when XBoard is set to 'fairy', can be determined by a
combobox control in the XBoard 'Engine Settings' menu dialog. This currently applies to the various army
combinations of chess with different armies. After having set this Variant fairy selects option,
activating XBoard's New game menu when already in variant fairy, or selecting fairy from the New variant
menu dialog will then start the selected game.

Fairymax supports multi-PV mode: by specifying a non-zero multi-PV margin in the Engine-Settings dialog
of XBoard, Fairy-Max will not only print the principal variation for the best move, but also for every
move that approaches the score of this best move to within the set margin. (If it does not find the best
move on the first try, this might lead to printing of a few extra lines below the threshold.) Fairy-Max
now also supports analysis mode, and exclusion of moves from the analysis.

The fmax.ini file from which Fairy-Max by default takes the piece and game definitions is a self-
documenting text file, which contains instructions for how to define new pieces and chess variants. In
addition it contains an extensive list of pre-defined pieces, incuding many not occurring in any of the
pre-defined variants, which the user can draw on to define his own variants.

Amongst the move types supported by Fairy-Max are normal leaper and slider moves, (e.g. knight and rook),
divergent moves (i.e. capture and non-capture moves can be different), hoppers (which jump over other
pieces, such as the Chinese cannon or the grasshopper), lame leapers (the move of which can be blocked on
squares they cannot move to, such as the Chinese horse and elephant), limited-range sliders (upto range
5), and any combination thereof, in every possible direction. The board width is configurable upto a
width of 14 files, and cylindrical boards (where left and right edge connect) are supported as well. The
board height can be configured up to 16 ranks.

OPTIONS

hashSize
If the first argument to fairymax is numeric, it is taken as an indicator for the amount of
memory Fairy-Max is allowed to use for its internal hash table. The default value for this
argument, 22, would result in a memory usage of 48MB. Each next-higher number doubles the memory
usage, each next-lower halves it. Running with less than 6MB (i.e. argument 19) is not
recommended. When fairymax is running under xboard 4.3.15 or later the hash-table size can be
set through the xboard menus, making this argument superfluous.

iniFile A second or non-numeric first argument is taken as a filename. Fairy-Max will use the mentioned
file in stead of its default fmax.ini file to define the movement of pieces and initial setup of
the variants. This makes it easier to define your own variants.

INTERACTIVE OPTIONS
Fairy-Max also supports some options that can only be set interactively, though XBoard's engine
settings menu dialog. These include a setting to further define -variant fairy, (e.g. which
armies to pit against each other in chess with different armies), and whether makruk is to be
played with Thai or Cambodian rules (the latter requiring XBoard's legality testing to be
switched off!). You can also enable resigning, and set a score threshold for when Fairy-Max
should do it, and define the already mentioned multi-PV margin there. An 'Info' button in the
settings dialog makes XBoard pop up a window with some info about the currently selected variant.

Persistent hash
Some of the interactive options can be used to store the current position in a file bearing the
name of the variant being played, with the extension '.hash' added to it, during analysis.
Positions in that file will be loaded into Fairy-Max' hash table before every game, protected
from overwrite. This can be used to create an opening or end-game book for the variant. The
Save in hash file button is convenient for saving the occasional position. For saving many
positions in a row the option Automatic pesistent-hash dialog can be ticked. This pops up a
dialog at the start of every analysis search, in which the user then just has to press 'OK' to
put the score from the analysis into the hash file. If a number is typed in that dialog before
pressing 'OK', the position will be saved with that score (in centi-Pawn) rather than the score
determined by the engine's own analysis. This can for instance be used to discourage opening
lines the engine overrates. The file will be created in the current directory, but at the start
of a game both this file, as well as one in Fairy-Max' private data files, will be loaded. The
install does contain such a persistent hash file for makruk, to help Fairy-Max find the checkmate
in the 'difficult' corners of the KMMMK and KNMMK (with like M) end-games.

AVAILABILITY

       At http://hgm.nubati.net/cgi-bin/gitweb.cgi the source code can be obtained.

STANDARDS

       WinBoard, xboard(6) interface ("Chess Engine Communication Protocol")

AUTHOR

       H.G.Muller <h.g.muller@hccnet.nl>.

       This manual page was generated with pod2man(1).