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>Getting Started with the Graphical Interface</TITLE
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>Gambit: Software Tools for Game Theory</TH
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><H1
><A
NAME="GUI.START"
>Getting Started with the Graphical Interface</A
></H1
><P
>This section gives a quick overview of the graphical interface,
using a simplified game of poker to illustrate the main features and
concepts.</P
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="GUI.POKER"
>A simple game of poker</A
></H1
><P
>This chapter takes a high-level tour of the Gambit graphical interface using
as an example the simple one-card poker game appearing in
[<SPAN
CLASS="CITATION"
><A
HREF="bib.html#MYE91"
>Mye91</A
></SPAN
>].

This game is included in the Gambit distribution
as <TT
CLASS="FILENAME"
>poker.efg</TT
>,
and can be found in the <TT
CLASS="FILENAME"
>efg</TT
>
subdirectory
of the directory in which Gambit is installed.  (For example, in the
standard installation under Microsoft Windows, this would be
<TT
CLASS="FILENAME"
>c:/Program Files/Gambit/efg/poker.efg</TT
>.)
By convention, files ending in
<TT
CLASS="FILENAME"
>.efg</TT
>
 store extensive form games, and files ending in
<TT
CLASS="FILENAME"
>.nfg</TT
> store normal form games. </P
><P
>When launched, Gambit displays a window similar to this:
<A
NAME="AEN138"
HREF="#FTN.AEN138"
>[1]</A
>
<P
><IMG
SRC="blankefg.png"></P
>
This window contains
a trivial extensive form game, containing exactly one node, which is both
root and terminal.  <A
HREF="gui.efg.html"
>the section called <I
>Extensive form games</I
> in the chapter called <I
>Graphical Interface Reference</I
></A
>
describes how to use the extensive form
window to construct and edit extensive form games.</P
><P
>There are three equivalent ways to open a saved game from any window in Gambit:
    <P
></P
><OL
TYPE="1"
><LI
><P
>	  Select the <B
CLASS="GUIMENUITEM"
>Open</B
> menu item from the
	  <B
CLASS="GUIMENU"
>File</B
> menu;
	  </P
></LI
><LI
><P
>	  Use the shortcut key combination 
	  <B
CLASS="KEYCAP"
>Ctrl</B
>-<B
CLASS="KEYCAP"
>O</B
>;
	</P
></LI
><LI
><P
>	  Click on the file folder icon on the toolbar.
	</P
></LI
></OL
>

Any of these actions leads to a dialog box for selecting a file to
open.  Use the dialog to locate and select the 
<TT
CLASS="FILENAME"
>poker.efg</TT
>
file.  After doing so, Gambit will display the opened game in a new
window:
<P
><IMG
SRC="poker.png"></P
>
The screenshot shows
the game as rendered by Gambit using the default settings.  Many
display options are available to customize the appearance of game trees;
see <A
HREF="gui.efg.html#GUI.EFG.DISPLAY"
>Changing how the tree is displayed</A
> for details.
  </P
><P
>The extensive form game tree is drawn with the root node at far left,
with branches going from left to right, and successive nodes to the
right of their predecessors.  Each node is represented as a horizontal
line.  Every non-terminal node is a decision node and is represented
by the color of the player who makes a decision at that node.  Nodes
are connected by branches, which are represented by two connected line
segments, which can be thought of as the "fork" and the
"tine".  The fork is used in the graphics display to indicate
graphically the probabilities of taking each branch.  The tine is used
as a location at which to display textual information about the
branch.
  </P
><P
>The poker game begins with Chance selecting either a Red card or
a Black card to deal to Player 1.  This is represented in the tree
by the grey node and subsequent branches labeled "Red" and "Black".
The forks of the branches have superimposed black lines stretching
halfway along the fork, indicating a probability of one-half that
each card is chosen.  After each of the two possible draws, Player 1,
whose nodes are colored in red, has the option to either "Raise" or
"Fold".  If Player 1 folds, the game ends; if he raises, Player2,
with nodes colored in blue,
then has the option to either "Meet" or "Pass" in either case,
the game ends after Player 2's choice.   All terminal nodes are drawn
in black in this picture.
  </P
><P
>In this game, outcomes are attached to each of the six terminal
nodes, and payoffs to the two players are indicated to the right
of the corresponding node, with Player 1's payoff listed first, then
Player 2's.  Outcomes are indicated to the right of nodes, but may
be attached to nonterminal nodes, in which case their payoffs are 
interpreted as incremental payoffs.   Outcomes may also be displayed
by textual name rather than by their payoff vector.
  </P
><P
>Information sets are identified by a pair of numbers.  The first
number indicates the number of the player who has the choice at the information
set.  The second number provides an identifying number for the
information set which is unique among that player's information sets.
Whenever possible, information sets are also
represented by vertical lines connecting the nodes that are members of
the same information set.
In this game, Player 1 observes which
card he has drawn prior to making his choice to "Raise" or
"Fold" ;
therefore, the node following Chance's "Red" move is in a separate
information set, numbered (1,1), from the node following Chance's
"Black" move, which is in information set (1,2).  Player 2, on the
other hand, does not observe Player 1's card, and so Player 2 has one
information set, numbered (2,1), with two member nodes connected by
a vertical line.
  </P
><P
>The analytical features of Gambit are located on the <B
CLASS="GUIMENU"
>Tools</B
>
menu.
<P
><IMG
SRC="efgtools.png"></P
>
These include:
<P
></P
><UL
><LI
><P
><B
CLASS="GUIMENUITEM"
>Dominance</B
>,
which interfaces to routines for identifying and eliminating
dominanted actions; </P
></LI
><LI
><P
><B
CLASS="GUIMENUITEM"
>Equilibrium</B
>,
which provedes access to
algorithms provided by Gambit to compute Nash equilibria of
the game;</P
></LI
><LI
><P
><B
CLASS="GUIMENUITEM"
>Qre</B
>,
which organizes Gambit's facilities for computing and manipulating
quantal response equilibria;</P
></LI
><LI
><P
><B
CLASS="GUIMENUITEM"
>Normal form</B
>,
which contains items to create normal
forms corresponding to the extensive form game.</P
></LI
></UL
>
The <B
CLASS="GUIMENUITEM"
>Dominance</B
>, 
<B
CLASS="GUIMENUITEM"
>Equilibrium</B
>, and
<B
CLASS="GUIMENUITEM"
>Normal form</B
> items will be discussed in the
next sections.</P
></DIV
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN138"
HREF="gui.start.html#AEN138"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>All the screenshots contained in this manual were
taken on a Linux system using the Sawfish window manager.
If you use a different operating system or window manager,
your windows may appear slightly differently.</P
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