| /* Template class for Dijkstra's algorithm on directed graphs. |
| Copyright (C) 2019-2021 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" |
| |
| enum shortest_path_sense |
| { |
| /* Find the shortest path from the given origin node to each |
| node in the graph. */ |
| SPS_FROM_GIVEN_ORIGIN, |
| |
| /* Find the shortest path from each node in the graph to the |
| given target node. */ |
| SPS_TO_GIVEN_TARGET |
| }; |
| |
| /* A record of the shortest path for each node relative to a special |
| "given node", either: |
| SPS_FROM_GIVEN_ORIGIN: |
| from the given origin node to each node in a graph, or |
| SPS_TO_GIVEN_TARGET: |
| from each node in a graph to the given target 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 *given_node, |
| enum shortest_path_sense sense); |
| |
| path_t get_shortest_path (const node_t *other_node) const; |
| int get_shortest_distance (const node_t *other_node) const; |
| |
| private: |
| const graph_t &m_graph; |
| |
| enum shortest_path_sense m_sense; |
| |
| /* For each node (by index), the minimal distance between that node |
| and the given node (with direction depending on m_sense). */ |
| auto_vec<int> m_dist; |
| |
| /* For each node (by index): |
| SPS_FROM_GIVEN_ORIGIN: |
| the previous edge in the shortest path from the origin, |
| SPS_TO_GIVEN_TARGET: |
| the next edge in the shortest path to the target. */ |
| auto_vec<const edge_t *> m_best_edge; |
| }; |
| |
| /* shortest_paths's constructor. |
| |
| Use Dijkstra's algorithm relative to GIVEN_NODE to populate m_dist and |
| m_best_edge with enough information to be able to generate Path_t instances |
| to give the shortest path... |
| SPS_FROM_GIVEN_ORIGIN: to each node in a graph from the origin node, or |
| SPS_TO_GIVEN_TARGET: from each node in a graph to the target node. */ |
| |
| template <typename GraphTraits, typename Path_t> |
| inline |
| shortest_paths<GraphTraits, Path_t>:: |
| shortest_paths (const graph_t &graph, |
| const node_t *given_node, |
| enum shortest_path_sense sense) |
| : m_graph (graph), |
| m_sense (sense), |
| m_dist (graph.m_nodes.length ()), |
| m_best_edge (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_best_edge.quick_push (NULL); |
| queue.quick_push (i); |
| } |
| m_dist[given_node->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; |
| } |
| } |
| if (idx_with_min_dist == -1) |
| break; |
| 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]); |
| |
| if (m_sense == SPS_FROM_GIVEN_ORIGIN) |
| { |
| 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_best_edge[dest->m_index] = succ; |
| } |
| } |
| } |
| else |
| { |
| int i; |
| edge_t *pred; |
| FOR_EACH_VEC_ELT (n->m_preds, i, pred) |
| { |
| // TODO: only for dest still in queue |
| node_t *src = pred->m_src; |
| int alt = m_dist[n->m_index] + 1; |
| if (alt < m_dist[src->m_index]) |
| { |
| m_dist[src->m_index] = alt; |
| m_best_edge[src->m_index] = pred; |
| } |
| } |
| } |
| } |
| } |
| |
| /* Generate an Path_t instance giving the shortest path between OTHER_NODE |
| and the given node. |
| |
| SPS_FROM_GIVEN_ORIGIN: shortest path from given origin node to OTHER_NODE |
| SPS_TO_GIVEN_TARGET: shortest path from OTHER_NODE to given target node. |
| |
| If no such path exists, return an empty path. */ |
| |
| template <typename GraphTraits, typename Path_t> |
| inline Path_t |
| shortest_paths<GraphTraits, Path_t>:: |
| get_shortest_path (const node_t *other_node) const |
| { |
| Path_t result; |
| |
| while (m_best_edge[other_node->m_index]) |
| { |
| result.m_edges.safe_push (m_best_edge[other_node->m_index]); |
| if (m_sense == SPS_FROM_GIVEN_ORIGIN) |
| other_node = m_best_edge[other_node->m_index]->m_src; |
| else |
| other_node = m_best_edge[other_node->m_index]->m_dest; |
| } |
| |
| if (m_sense == SPS_FROM_GIVEN_ORIGIN) |
| result.m_edges.reverse (); |
| |
| return result; |
| } |
| |
| /* Get the shortest distance... |
| SPS_FROM_GIVEN_ORIGIN: ...from given origin node to OTHER_NODE |
| SPS_TO_GIVEN_TARGET: ...from OTHER_NODE to given target node. */ |
| |
| template <typename GraphTraits, typename Path_t> |
| inline int |
| shortest_paths<GraphTraits, Path_t>:: |
| get_shortest_distance (const node_t *other_node) const |
| { |
| return m_dist[other_node->m_index]; |
| } |
| |
| #endif /* GCC_SHORTEST_PATHS_H */ |