This chapter introduces several more commands used while playing games and matches in @gnubg{}.
new game
new game
will set up the board in the starting position, and roll one die for
each player for the opening move.
If you are in the middle of a game, new game will ask you if
you want to abort the game in progress. If you do, a new game will
replace the current one (i.e. the partially completed game will have
no effect on the score). If you want the current game to be scored
for either player, you should use the resign command instead.
move from to ...
move =number
from to ...
=number
move command allows you to make chequer plays when it is your
turn. In its normal form, you should specify pairs of point numbers
indicating the points you want to move a chequer from and to. Specify
one pair for each chequer you want to move. (For instance, on an
opening roll of 31, you might use move 8 5 6 5 to move two
chequers -- one from your 8 point to your 5 point, and the other from
your 6 point to your 5 point.) For several example moves, see
section Sample Game.
You should use the words bar and off when moving a chequer
from the bar or bearing it off the board, e.g. move bar 20 or
move 3 off. These words can be abbreviated to b and
o respectively.
If there is only one legal move you can make, then the command move
by itself will make it for you without requiring you to specify it in full.
Similarly, if there is no play available at all, then move will
end your turn without moving.
As long as you specify at least one pair of points, then the word
move is optional -- the command bar 20 24 20 means exactly
the same thing as move bar 20 24 20, for instance.
FIXME document `=n' notation.
If you are using a window system, you can also move chequers using the
board window. One way to do this is to use any mouse button to drag a
chequer (that is, press the button when the pointer is over the chequer
you wish to move; move the pointer to the point you wish to play it to,
and then release the button).
An alternative is to click a mouse button on the chequer; button 1 will
move it by the number of pips showing on the left die, and any other
button will move it according to the right die. If you don't like the
order the dice are displayed in, pressing either button 2 or 3 on the
dice will swap their positions.
Whichever method you use to move the chequers, once you have made a legal
move you can end your turn by clicking mouse button 1 on the dice.
FIXME reference set auto move and set auto bearoff.
resign [type]
agree
accept
decline
reject
resign command is used to give up a game without playing it to
completion. It is often useful during endgame play when the game reaches
a position where it is impossible for one player to win. If you do not
specify a value type, then the player whose turn it is offers to
give up one game (at the current cube value) to the opponent; you can
also specify 1, 2 or 3 to resign a single, double
or triple game. Specifying normal, gammon or
backgammon is also legal, and is identical to expressing the
number of points as a digit. single is yet another synonym for
one game.
The opponent may accept the resignation with either the agree or
accept commands, but is not obliged to. To ignore the
resignation and continue play normally, use either the decline or
reject commands. (accept and reject are also legal
commands in response to a double; see section The Doubling Cube.)
set board id|=number
set board command. You need to know the
position ID of the chequer arrangement you want; position IDs
are always displayed when the board is shown. (If you are playing
on a text terminal, the position ID is in the upper right hand corner
of the board diagram; when using the board window, the ID is shown
below the board on the right hand side.) For instance, to set the
chequers to the starting position, use the command
set board 4HPwATDgc/ABMA.
FIXME reference =n notation and describe the GTK edit mode
show board [id|=number]
show board command is used to display a particular position ---
normally the board of the current game, but it is also possible to view
unrelated layouts. When specified without the optional id parameter,
the current position is displayed. (When using a text terminal, this
is useful if subsequent output has caused the board diagram to scroll
off the screen. In the board window, the command can be used to undo
erroneous chequer plays by resetting the window to the position at the
start of the turn.)
When a position ID id is given, the chequers are arranged into
the position specified and that board is displayed. Note that this
command affects the display only; the current game is unchanged. Use
the show board command with no parameter if you want to see
the current game again.
hint
hint command to see the moves @gnubg{} recommends.
The output is of the following form:
Win W(g) W(bg) L(g) L(bg) Equity Move 0.542 0.142 0.008 0.113 0.008 (+0.114) 6/5 8/5 0.505 0.120 0.008 0.122 0.007 (+0.009) 24/23 23/20 0.498 0.126 0.008 0.123 0.007 (+0.000) 24/23 13/10 0.499 0.113 0.008 0.121 0.007 (-0.011) 24/23 24/21 0.486 0.125 0.008 0.120 0.009 (-0.024) 13/10 10/9 0.481 0.116 0.008 0.129 0.008 (-0.051) 6/5 24/21 0.472 0.122 0.008 0.129 0.009 (-0.064) 6/5 13/10The moves are listed in descending order of preference, so in this case, @gnubg{} recommends the move `6/5 8/5'. The first five columns are its estimates of the probability of the player on roll winning (`Win'), winning a gammon (`W(g)'), winning a backgammon (`W(bg)'), losing a gammon (`L(g)'), and losing a backgammon (`L(bg)') if the game is played to completion without use of the doubling cube, after the candidate move in that row is made(1). The sixth column, `Equity', is the estimated cubeless equity following the move --- this is the expected number of points per game won by the player on roll. FIXME describe =n notation. @gnubg{} will `look ahead' a certain number of moves when evaluating the probabilities, according to the search depth set by the
set plies command (see section Using @gnubg{} to Analyse Positions).
show pipcount [id|=number]
show pipcount to automatically count the number of `pips'
each player needs to bear off. Depending on the position, the output
will look something like:
The pip counts are: X 103, O 112.
show player
set player name human
set player old-name name new-name
show player to summarise these settings. By default,
@gnubg{} will play for player 0, whose name is initially `gnubg'.
Player 1 defaults to a human (i.e. @gnubg{} will prompt the user
for a move when it is player 1's turn) whose name is the user's login
name, on systems where this information is available; on single-user
systems, the default name `user' applies.
Either player can be set to a human with the command set player
name human, where name is either the number of the player
(0 or 1) or that player's name (initially `gnubg' and `user'
or the user's login name). You can also specify both which will
set both players simultaneously. There are also options for computer
players (see section Having @gnubg{} Make Moves).
You can change the names of the players with the
set player old-name name new-name command. Again,
either the player numbers or names are valid for the old-name
parameter. Names may not contain whitespace characters, and may not
be longer than 31 characters. The names `0', `1' and
`both' are not permitted, to avoid ambiguities, and the players
may not both share the same name. Names are not case sensitive.
set turn player
show turn
set turn player (where player can be the
player's name or number, as above) is used to control which player is on
roll. It will cancel the current dice roll and cube action (if any),
and set the named player on roll.
set automatic bearoff
set automatic move
set display value
set display off will suppress this output, which can
speed up the display and reduce clutter (this might be useful when completing
a game where both sides are played by the computer, for instance).
set display on will restore the default behaviour. The standard
toggle synonyms may be substituted for on and off.
The board will always be updated when it is a human player's turn to move,
regardless of the display setting.
roll
set automatic roll value
set automatic roll command
instructs @gnubg{} to go ahead and roll the dice without waiting for the
player to issue roll, whenever no doubling decision is necessary.
The standard toggle commands may be used to turn this option on and off.
set dice pips pips
set dice command. The player can then play a move
according to the dice specified. Like the roll command, this will
also forego any opportunity to double; to disregard a dice roll and
allow the player to roll again (or double, if permitted), use set
turn player.
set rng generator [seed]
show rng
set rng command is used to select which generator will be used.
The generator parameter must be one of the following:
ansi
rand() random number generator. The
behaviour of this generator will depend on the C library linked with
@gnubg{}, but is typically a linear congruential pseudo-random number
generator. Such generators have fairly weak distribution properties,
but are generally adequate for producing backgammon dice. However, the
ANSI generator is not recommended for performing rollouts, because any
small biases in the dice could accumulate over hundreds or thousands of
trials and distort the results. Using a better generator would be
safer for rollouts.
bsd
random() non-linear additive feedback random number
generator. This is a good quality generator, but is not available on
all systems. @gnubg{} will report an error if you attempt to use this
generator if the C library used in your installation does not include
the BSD random code.
isaac
manual
manual, @gnubg{} will not generate
the dice itself; rather, it will prompt for a roll to be entered whenever
one is required.
md5
show seed is available
when using the md5 generator, for obtaining the current seed value.
mersenne
user
user generator to dynamically load a user library which
will be used to produce the dice rolls. See the file `userrng.c'
in the @gnubg{} distribution for an example user generator, and instructions
on how to write your own.
set seed seed
set seed command. FIXME
show seed
set player name gnubg
set player name pubeval
pubeval. This will cause moves for that player to be made by
Gerry Tesauro's benchmark player. pubeval is much weaker than
@gnubg{}'s own evaluator, but provides a constant level of play which
is useful for measuring different players against.
pubeval is not capable of making cube or resignation decisions
based on the position. It will never accept resignations at less than
triple (backgammon) stakes, and will take all cubes. It nevers offers
resignations or doubles of its own.
set player name external
set player name evaluation
play
external
This section describes how to use GNU Backgammon to play series of games, whether those games are part of a match (as in tournament backgammon) or a session of independent games (conventionally called "money" play, regardless of whether any payment is involved).
new match length
new session
set automatic game
set crawford
set postcrawford
set automatic crawford
set jacoby
set automatic doubles limit
set score points points
show crawford
show postcrawford
show jacoby
show score
double
redouble
beaver
take
accept
drop
pass
reject
set cube centre
set cube owner player
set cube use
set cube value points
save game file
save match file
load game file
load match file