Changes between Version 1 and Version 2 of soc/2007/UserFriendlyGraphs/Distance

Timestamp:

Jul 6, 2007, 4:30:53 PM (15 years ago)

Author:

Andrew Sutton

Comment:

--

soc/2007/UserFriendlyGraphs/Distance

@@ -9 +9 @@
   Returns the (arithmatic) mean of shortest paths between `v` and all other vertices in `g`.
 
-`closeness`
+`closeness(g, v, dist)`
 
-`eccentricity`
+`eccentricity(g, v, dist)`
 
 We can also define the following graph measures:
 
-`radius`
+`radius(g, dist)`
 
-`diameter`
+`diameter(g, dist)`
+
+== Problems with Matrices ==
+One of the problems with inclusive graph measure computations is that they usually need a matrix of all pairs of shortest paths. The output matrix of this type for the all-pairs functions is described as a DistanceMatrix. This varies considerably from property maps since we're essentially talking about a 2D version of it. In fact, the documentation doesn't even mention property maps here - just that the type has to satisfy the expression `D[u][v]` where `u` and `v` are vertices and the result of the expression is the value type of `weight_map`.
+
+The problem comes from satisfying the return type in a generic function. If the matrix is given as `vector<vector<X>>`, then the return type is `vector<vector<>::value_type>::value_type`. Unfortunately, if its a `unordered_map<Vertex, unordered_map<Vertex, X>>`, then the return type is even more complicated.
+
+One (easy) solution is to simply require the use of a weight map parameter.