## Mercurial > hg > CbC > CbC_gcc

### view gcc/shortest-paths.h @ 158:494b0b89df80 default tip

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author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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date | Mon, 25 May 2020 18:13:55 +0900 |

parents | 1830386684a0 |

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/* Template class for Dijkstra's algorithm on directed graphs. Copyright (C) 2019-2020 Free Software Foundation, Inc. Contributed by David Malcolm <dmalcolm@redhat.com>. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>. */ #ifndef GCC_SHORTEST_PATHS_H #define GCC_SHORTEST_PATHS_H #include "timevar.h" /* A record of the shortest path to each node in an graph from the origin node. The constructor runs Dijkstra's algorithm, and the results are stored in this class. */ template <typename GraphTraits, typename Path_t> class shortest_paths { public: typedef typename GraphTraits::graph_t graph_t; typedef typename GraphTraits::node_t node_t; typedef typename GraphTraits::edge_t edge_t; typedef Path_t path_t; shortest_paths (const graph_t &graph, const node_t *origin); path_t get_shortest_path (const node_t *to) const; private: const graph_t &m_graph; /* For each node (by index), the minimal distance to that node from the origin. */ auto_vec<int> m_dist; /* For each exploded_node (by index), the previous edge in the shortest path from the origin. */ auto_vec<const edge_t *> m_prev; }; /* shortest_paths's constructor. Use Dijkstra's algorithm relative to ORIGIN to populate m_dist and m_prev with enough information to be able to generate Path_t instances to give the shortest path to any node in GRAPH from ORIGIN. */ template <typename GraphTraits, typename Path_t> inline shortest_paths<GraphTraits, Path_t>::shortest_paths (const graph_t &graph, const node_t *origin) : m_graph (graph), m_dist (graph.m_nodes.length ()), m_prev (graph.m_nodes.length ()) { auto_timevar tv (TV_ANALYZER_SHORTEST_PATHS); auto_vec<int> queue (graph.m_nodes.length ()); for (unsigned i = 0; i < graph.m_nodes.length (); i++) { m_dist.quick_push (INT_MAX); m_prev.quick_push (NULL); queue.quick_push (i); } m_dist[origin->m_index] = 0; while (queue.length () > 0) { /* Get minimal distance in queue. FIXME: this is O(N^2); replace with a priority queue. */ int idx_with_min_dist = -1; int idx_in_queue_with_min_dist = -1; int min_dist = INT_MAX; for (unsigned i = 0; i < queue.length (); i++) { int idx = queue[i]; if (m_dist[queue[i]] < min_dist) { min_dist = m_dist[idx]; idx_with_min_dist = idx; idx_in_queue_with_min_dist = i; } } gcc_assert (idx_with_min_dist != -1); gcc_assert (idx_in_queue_with_min_dist != -1); // FIXME: this is confusing: there are two indices here queue.unordered_remove (idx_in_queue_with_min_dist); node_t *n = static_cast <node_t *> (m_graph.m_nodes[idx_with_min_dist]); int i; edge_t *succ; FOR_EACH_VEC_ELT (n->m_succs, i, succ) { // TODO: only for dest still in queue node_t *dest = succ->m_dest; int alt = m_dist[n->m_index] + 1; if (alt < m_dist[dest->m_index]) { m_dist[dest->m_index] = alt; m_prev[dest->m_index] = succ; } } } } /* Generate an Path_t instance giving the shortest path to the node TO from the origin node. */ template <typename GraphTraits, typename Path_t> inline Path_t shortest_paths<GraphTraits, Path_t>::get_shortest_path (const node_t *to) const { Path_t result; while (m_prev[to->m_index]) { result.m_edges.safe_push (m_prev[to->m_index]); to = m_prev[to->m_index]->m_src; } result.m_edges.reverse (); return result; } #endif /* GCC_SHORTEST_PATHS_H */