# Ticket #4737 (closed Bugs: fixed)

## Documentation for Prim MST concerning distance_map is wrong

Reported by: | nicoe@… | Owned by: | asutton |
---|---|---|---|

Milestone: | To Be Determined | Component: | graph |

Version: | Boost 1.44.0 | Severity: | Problem |

Keywords: | Cc: |

### Description

In the documentation for prim_minimum_spanning_tree, you can read at distance_map:

The shortest path weight from the source vertex s to each vertex in the graph g is recorded in this property map. The shortest path weight is the sum of the edge weights along the shortest path.

I would say this is wrong. I claim that the prim_minimum_spanning_tree stores original edgeweights in the distance map. Precisely, an entry i in the distance map corresponds to the edgeweight of the edge from vertex i to its predecessor in the MST.

Example: Given a undirected graph on the vertex set {0,1,2} with edges (0,1,2), (0,2,3), (1,2,4) (to be read as vertex, vertex, weight). The output of prim MST called with parameters root_vertex(1) concerning the distance map is (2,0,3). According to the documentation it schould be (2,0,5).

See attached example for details

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