cz.cuni.astar
Interface AStarGoal

All Known Implementing Classes:

GameMapAStarGoal

public interface AStarGoal

This class defines the goal of A* algorithm, it affects how the A* works. When implementing this class you may a few several things. 1) extra cost for edges between two nodes 2) wether A* may use the node (this is useful when you want to forbig some nodes / states) 3) heuristic function which estimates the distance from node to the goal node !NOTE! That this heuristic must be correct for A* to work correctly, that means the returned distance must be smaller or equal to the real distance. (In 2D, 3D a euklidian metric will do the job). Open and Close list will also be stored in this class - that's because after the A* finish the job you might be interested what's inside them. When you providing a AStarGoal to a AStar.aStar() be sure that AStarOpenList and AStarCloseList is empty!

Method Summary

int	getEstimatedDistanceToGoal(java.lang.Object node) This is heuristic function. !
int	getExtraCost(java.lang.Object nodeFrom, java.lang.Object nodeTo) Returns extra cost to add to value when trying to go nodeFrom to nodeTo ... of course it can depends only on nodeTo (some special kind of a floor for instance) Don't worry about the edge cost to become negative, A* ensures that that the least cost is 0 (Algorithm can't work over graphs with negative costs.)
boolean	isGoalReached(java.lang.Object actualNode) Returns true, if we've reached the goal ... e.g. actualNode is node we were trying to get to if this function never returns true, A* will run until all nodes are evaluated
boolean	isNodeOpened(java.lang.Object node) Returns true if A* can use this node (e.g. to step on this type of floor) You can use it to forbid some specific nodes
void	setCloseList(java.util.Collection closeList) This is called at the beggining of the A* algorithm to bind the close list to the goal (you may use it check which nodes we've visited, etc... for extra cost for instance).
void	setOpenList(java.util.Collection openList) This is called at the beggining of the A* algorithm to bind the open list to the goal (you may use it check which nodes we've visited, etc... for extra cost for instance).

Method Detail

setOpenList

void setOpenList(java.util.Collection openList)

This is called at the beggining of the A* algorithm to bind the open list to the goal (you may use it check which nodes we've visited, etc... for extra cost for instance). DON'T CHANGE IT!

setCloseList

void setCloseList(java.util.Collection closeList)

This is called at the beggining of the A* algorithm to bind the close list to the goal (you may use it check which nodes we've visited, etc... for extra cost for instance). DON'T CHANGE IT!

getEstimatedDistanceToGoal

int getEstimatedDistanceToGoal(java.lang.Object node)

This is heuristic function. !NOTE! That this heuristic must be correct for A* to work correctly, that means the returned distance must be smaller or equal to the real distance. (In 2D, 3D a euklidian metric will do the job).

Returns:

how far is to the goal from the node

isNodeOpened

boolean isNodeOpened(java.lang.Object node)

Returns true if A* can use this node (e.g. to step on this type of floor) You can use it to forbid some specific nodes

getExtraCost

int getExtraCost(java.lang.Object nodeFrom,
                 java.lang.Object nodeTo)

Returns extra cost to add to value when trying to go nodeFrom to nodeTo ... of course it can depends only on nodeTo (some special kind of a floor for instance) Don't worry about the edge cost to become negative, A* ensures that that the least cost is 0 (Algorithm can't work over graphs with negative costs.)

Returns:

extra cost of edge for nodeFrom -> nodeTo

isGoalReached

boolean isGoalReached(java.lang.Object actualNode)

Returns true, if we've reached the goal ... e.g. actualNode is node we were trying to get to if this function never returns true, A* will run until all nodes are evaluated

Parameters:

actualNode -