tesuji.games.go.computer.evaluation
Class Influence
java.lang.Object
|
+--tesuji.games.go.ByteArrayImpl
|
+--tesuji.games.go.computer.evaluation.Influence
- All Implemented Interfaces:
- BoardChangeListener, ByteArray, java.util.EventListener
- public class Influence
- extends ByteArrayImpl
- implements BoardChangeListener
This class computes influence from black and white stones
given a certain board-position.
The basic algorithm is quite simple:
- Each black stone gets a high positive value.
- Each white stone gets a high negative value.
- For several iterative steps, each point that has a positive
value adds 1 to the influence of the neighbouring points.
Each point that has a negative value subtracts 1 from the
influence of the neighbouring points.
This is also called the Zobrist influence algorithm, since I think
he was te first to come with this scheme.
A possible variation on this is that if an empty point has
two stones as its direct neighbours of opposite color facing
each other, its influence is always 0. A fair part of the
implementation deals with these so called 'dame' points.
A straightforward implementation of this influence algorithm would
be to loop over the entire board for each iteration, and update
the influence of the neighbouring points depending on whether the
influence of the current point is positive or negative. To prevent
the newly calculated values to affect the old values, this has to
be done in two passes. So for each iteration, two loops over the
whole board would be necessary. However, most of the time when a
new move is played, the influence of the new position is usually
still very similar to that of the previous position. When the board
gets full, a new move only affects a handful number of points.
The implementation here is much more efficient than the straightforward
approach since it only does the minimal amount of work necessary to
compute the influence of the new position, based on its previous
computation. This algorithm works even when the new position is
completely different from the previous one, although in that case no
time is saved compared to the straightforward approach. But if the
new position is very similar to the old one, only a very limited
amount of work needs to be done. It makes this implementation often
a hundred times faster than the straightforward one.
The actual algorithm is not described in detail here, but it's probably
the most elegant one I ever designed.
Creation date: (17-May-01 4:05:10 PM)
Product: Tesuji Software Go Library.
Copyright (c) 2001 Tesuji Software B.V.
All rights reserved.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, and/or sell copies of the Software, and to permit persons
to whom the Software is furnished to do so, provided that the above
copyright notice(s) and this permission notice appear in all copies of
the Software and that both the above copyright notice(s) and this
permission notice appear in supporting documentation.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of a Tesuji Software
shall not be used in advertising or otherwise to promote the sale, use
or other dealings in this Software without prior written authorization
of Tesuji Software.
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
MAX_ITERATIONS
public static final int MAX_ITERATIONS
BLACK_STONE
public static final byte BLACK_STONE
WHITE_STONE
public static final byte WHITE_STONE
Influence
public Influence(int boardSize)
addBoardChangeListener
public void addBoardChangeListener(BoardChangeListener l)
- Any listener that registers through this method will get
notified of all the points where the influence changed.
Creation date: (18-May-01 12:01:03 AM)
changeBoard
public void changeBoard(int x,
int y,
byte value,
byte oldValue)
- Mark a point on the board as changed. This will cause the
influence to be updated taking the new value into consideration
the next time the method update is called.
Creation date: (17-May-01 4:33:51 PM)
- Specified by:
changeBoard
in interface BoardChangeListener
clear
public void clear()
getPreviousInfluence
public ByteArray getPreviousInfluence()
removeBoardChangeListener
public void removeBoardChangeListener(BoardChangeListener l)
setDameSwitch
public void setDameSwitch(boolean flag)
- Switch the 'dame' feature on or off.
Creation date: (19-May-01 4:18:35 PM)
update
public void update()
- Compute the influence based on the changes made to
the board (by using changeBoard) since this method
was last called.
Creation date: (17-May-01 4:41:41 PM)