lengauer_tarjan_dominator_tree: doesn't respect indexMap parameter

[Justin Viiret <justin.viiret@…>]

The more complex version of lengauer_tarjan_dominator_tree, as described in the BGL documentation, takes a parameter indexMap which is to be used as the index map of the graph.

However, if you look at the code for lengauer_tarjan_dominator_tree_without_dfs (which is called by the lengauer_tarjan_dominator_tree function), the indexMap argument is not used, and instead the dominator_visitor just uses get(vertex_index, g) explicitly when constructing its internal property maps.

This means that graphs that do not have a vertex_index property can't use the algorithm.

I believe the correct fix is to pass the provided index map into the dominator_visitor constructor, and use it when constructing the other maps held by the visitor.

[Justin Viiret <justin.viiret@…>]

I have created a pull request on github for boostorg/graph with a small patch that addresses this issue here:

​https://github.com/boostorg/graph/pull/49.

[Noel Belcourt]

Just pushed your PR, thanks for the patch!