From b7b7ab505a1cd374370a03cc61ca08f92ab8c075 Mon Sep 17 00:00:00 2001 From: Francois Fleuret Date: Wed, 2 Jan 2013 03:23:40 +0100 Subject: [PATCH] Simplified and optimized compute_dp_ordering. --- mtp_graph.cc | 22 ++++------------------ 1 file changed, 4 insertions(+), 18 deletions(-) diff --git a/mtp_graph.cc b/mtp_graph.cc index a03f60e..4cfd1f8 100644 --- a/mtp_graph.cc +++ b/mtp_graph.cc @@ -424,23 +424,15 @@ int MTPGraph::retrieve_one_path(Edge *e, Path *path) { ////////////////////////////////////////////////////////////////////// -static int compare_vertices_on_distance(const void *v1, const void *v2) { - scalar_t delta = - (*((Vertex **) v1))->distance_from_source - - (*((Vertex **) v2))->distance_from_source; - if(delta < 0) return -1; - else if(delta > 0) return 1; - else return 0; -} - void MTPGraph::compute_dp_ordering() { Vertex *v; Edge *e; int ntv; - // This method computes for each node the length of the longest link - // from the source, and orders the node in _dp_order according to - // it. It aborts if the graph is not a DAG. + // This method orders the nodes by putting first the ones with no + // predecessors, then going on adding nodes whose predecessors have + // all been already added. Computing the distances from the source + // by visiting nodes in that order is equivalent to DP. int *nb_predecessors = new int[_nb_vertices]; @@ -464,12 +456,10 @@ void MTPGraph::compute_dp_ordering() { } } - scalar_t rank = 1; while(already_processed < front) { new_front = front; while(already_processed < front) { v = *(already_processed++); - v->distance_from_source = rank; for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) { ntv = int(e->terminal_vertex - _vertices); nb_predecessors[ntv]--; @@ -480,7 +470,6 @@ void MTPGraph::compute_dp_ordering() { } } front = new_front; - rank++; } if(already_processed < _dp_order + _nb_vertices) { @@ -489,9 +478,6 @@ void MTPGraph::compute_dp_ordering() { } delete[] nb_predecessors; - - for(int v = 0; v < _nb_vertices; v++) { _dp_order[v] = &_vertices[v]; } - qsort(_dp_order, _nb_vertices, sizeof(Vertex *), compare_vertices_on_distance); } ////////////////////////////////////////////////////////////////////// -- 2.39.5