AStar Visitor Concept

This concept defines the visitor interface for astar_search(). Users can define a class with the AStar Visitor interface and pass an object of the class to astar_search(), thereby augmenting the actions taken during the graph search.

Refinement of

Copy Constructible (copying a visitor should be a lightweight operation).

Notation

V A type that is a model of AStar Visitor.
vis An object of type V.
G A type that is a model of Graph.
g An object of type G.
e An object of type boost::graph_traits<G>::edge_descriptor.
s,u,v An object of type boost::graph_traits<G>::vertex_descriptor.
d An object of type DistanceMap.
WeightMap A type that is a model of Readable Property Map.
w An object of type WeightMap.

Associated Types

none

Valid Expressions

NameExpression Return Type Description
Initialize Vertex vis.initialize_vertex(u, g) void This is invoked on each vertex of the graph when it is first initialized (i.e., when its property maps are initialized).
Discover Vertex vis.discover_vertex(u, g) void This is invoked when a vertex is first discovered and is added to the OPEN list.
Examine Vertex vis.examine_vertex(u, g) void This is invoked on a vertex as it is popped from the queue (i.e. it has the lowest cost on the OPEN list). This happens immediately before examine_edge() is invoked on each of the out-edges of vertex u.
Examine Edge vis.examine_edge(e, g) void This is invoked on every out-edge of each vertex after it is examined.
Edge Relaxed vis.edge_relaxed(e, g) void Upon examination, if the following condition holds then the edge is relaxed (the distance of its target vertex is reduced) and this method is invoked: 
tie(u, s) = incident(e, g);
D d_u = get(d, u), d_v = get(d, s);
W w_e = get(w, e);
assert(compare(combine(d_u, w_e), d_s));
Edge Not Relaxed vis.edge_not_relaxed(e, g) void Upon examination, if an edge is not relaxed (see above), then this method is invoked.
Black Target vis.black_target(e, g) void This is invoked when a vertex that is on the CLOSED list is ``rediscovered'' via a more efficient path, and is re-added to the OPEN list.
Finish Vertex vis.finish_vertex(u, g) void This is invoked on a vertex when it is added to the CLOSED list, which happens after all of its out edges have been examined.

Models

See also

Visitor concepts

Copyright © 2004 Kristopher Beevers, Rensselaer Polytechnic Institute ([email protected])

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