5.7KB
title: Libre Blackjack subtitle: A free blackjack back end desc: a completely free-as-in-freedom blackjack engine designed to study and analyze the game statistics using different playing strategies ranging from simple card counting up to other complex algorithms based on artificial intelligence. author: Jeremy Theler date: December 20, 2020 version: libreblackjackversion infoname: blackjack
lang: en-US
Overview
include(overview.md)
Running blackjack
Invocation
The format for running the blackjack program is:
blackjack [options] [path_to_conf_file]
If no configuration file is given, a file named blackjack.conf in the current directory is used, provided it exists.
With no options and no configuration file, blackjack starts in interactive mode and it is ready to start a blackjack game.
The blackjack executable supports the following options:
include(help.md)
All the options which can be given in the configuration file can be passed as a command-line argument. For example, running
blackjack --decks=4 --no_insurance=true
is equivalent to using a configuration file with
decks = 4
no_insurance = true
Interactive game
If blackjack is attached to an interactive TTY (i.e. neither the standard input nor outputs are redirected), an interactive game is triggered. First thing the program will do is to ask for a bet:
LibreBlackjack v0.2+Δ
a free & open blackjack engine
Starting new hand #1 with bankroll 0
<-- Bet?
>
So the user should enter a number, say “1” and then press Enter and then a game will be dealt:
Player's card is Q♥
Dealer's up card is 10♠
Player's card is Q♣
Dealer's hole card is dealt
No blackjacks
-- Dealer's hand: --------
_____ _____
|10 | |#####|
| | |#####|
| ♠ | |#####|
| | |#####|
|___10| |#####|
Value: 10
-- Player's hand --------
_____ _____
|Q | |Q |
| | | |
| ♥ | | ♣ |
| | | |
|____Q| |____Q|
Value: 20
<-- Play? 20 10
>
A flat-betting game can be played by passing --flat_bet=true through the command line.
Commands
The dealer (he) and the player (she) “talk” through commands, which are ASCII strings sent through any of the different IPC mechanisms discussed in [Automated playing through IPC]. In the most basic case, a human player reads commands from the dealer from blackjack’s standard output and writes her commands into the dealer’s standard input. Those commands from the dealer that require a particular action from the player end with a quotation sign such as bet?, insurance? or play?.
All numerical values such as hand totals or bankrolls are given as decimal ASCII strings.
From the dealer to the player
From the player to the dealer
The following commands are available for the player for playing her hand.
include(input-particular.md)
The following are general commands in the sense that they can be sent from the player to the dealer at any moment of the game.
include(input-general.md)
Configuration file
Libre Blackjacks reads a configuration file that contains
- settings about the rules of the game
- number of decks,
- whether if the dealer has to hit soft seventeen or not,
- blackjack payout,
- maximum bet allowed,
- etc…
- how the player is supposed to play
- number of hands
- whether a flat or variable bet is going to be used,
- etc…
- if there are any particular shoe arrangement, i.e. a predefined set of cards dealt in a certain order for instance to play one million hands of a sixteen against a dealer’s ten
- what kind of information is shown in the interactive session
- if ASCII-art cards are supposed to be shown,
- a real-time delay to make the game smoother,
- etc.
- how the automated player communicates with the dealer
- using standard input/output,
- FIFO named pipes,
- POSIX message queues,
- POSIX shared memory,
- etc…
The location of the configuration file can be given in the command line. If none is provided, a file named blackjack.conf in the current directory is used. If such file does not exists, the defaults values of each variable are used. Individual variables can be set from the command line by passing one or more times the option --configuration_variable[=value] in the [invocation].
Comments can be inserted using either a hash # or a colon ;. The following configuration file is the default provided in the main distribution tarball:
# uncomment the following line to arrange cards
# arranged_cards = 1 5 14 9 27
flat_bet = 1 # do not ask for bets
no_insurance = 1 # do not ask for insurance
decks = 1 # number of decks, negative means infinite
Variables and values
include(conf.md)
Dumb internal player
Example automated players
The directory players contains a few examples of automated player, which are discussed in the following sections. A script check.sh runs some of them and compares the expected value of the bankroll relative to the number of hands which each player obtains with the theoretical expected value (according to the game rules and player’s strategy) within an allowed statistical uncertainty. This scripts writes the following table (actual values might vary depending on the random nature of the game):
include(../players/check.md)
The columns are
- Case name, as discussed below.
- Expected theoretical result in absolute units (i.e. -0.01 means -1%)
- Actual result obtained by Libre Blackjack in absolute units
- Estimated error equal to the standard deviation of the result
- Whether the result coincides or not with the theoretical value
include(players.md)