@@ -73,7 +73,7 @@ class epath_finder
public:
epath_finder (const exploded_graph &eg)
: m_eg (eg),
- m_sep (eg, eg.get_origin ())
+ m_sep (eg, eg.get_origin (), SPS_FROM_GIVEN_ORIGIN)
{
}
@@ -147,7 +147,8 @@ test_shortest_paths ()
/* Use "A" as the origin; all nodes should be reachable. */
{
- shortest_paths<test_graph_traits, test_path> sp (g, a);
+ shortest_paths<test_graph_traits, test_path> sp (g, a,
+ SPS_FROM_GIVEN_ORIGIN);
test_path path_to_a = sp.get_shortest_path (a);
ASSERT_EQ (path_to_a.m_edges.length (), 0); /* Trivial path. */
@@ -181,7 +182,8 @@ test_shortest_paths ()
/* Use "B" as the origin, so only E and F are reachable. */
{
- shortest_paths<test_graph_traits, test_path> sp (g, b);
+ shortest_paths<test_graph_traits, test_path> sp (g, b,
+ SPS_FROM_GIVEN_ORIGIN);
test_path path_to_a = sp.get_shortest_path (a);
ASSERT_EQ (path_to_a.m_edges.length (), 0); /* No path. */
@@ -207,7 +209,8 @@ test_shortest_paths ()
/* Use "C" as the origin, so only D and F are reachable. */
{
- shortest_paths<test_graph_traits, test_path> sp (g, c);
+ shortest_paths<test_graph_traits, test_path> sp (g, c,
+ SPS_FROM_GIVEN_ORIGIN);
test_path path_to_a = sp.get_shortest_path (a);
ASSERT_EQ (path_to_a.m_edges.length (), 0); /* No path. */
@@ -229,6 +232,36 @@ test_shortest_paths ()
ASSERT_EQ (path_to_f.m_edges.length (), 1);
ASSERT_EQ (path_to_f.m_edges[0], cf);
}
+
+ /* Test of SPS_TO_GIVEN_TARGET. Use "F" as the target. */
+ {
+ shortest_paths<test_graph_traits, test_path> sp (g, f,
+ SPS_TO_GIVEN_TARGET);
+
+ test_path path_to_a = sp.get_shortest_path (a);
+ ASSERT_EQ (path_to_a.m_edges.length (), 2);
+ ASSERT_EQ (path_to_a.m_edges[0], ac);
+ ASSERT_EQ (path_to_a.m_edges[1], cf);
+
+ test_path path_to_b = sp.get_shortest_path (b);
+ ASSERT_EQ (path_to_b.m_edges.length (), 2);
+ ASSERT_EQ (path_to_b.m_edges[0], be);
+ ASSERT_EQ (path_to_b.m_edges[1], ef);
+
+ test_path path_to_c = sp.get_shortest_path (c);
+ ASSERT_EQ (path_to_c.m_edges.length (), 1);
+ ASSERT_EQ (path_to_c.m_edges[0], cf);
+
+ test_path path_to_d = sp.get_shortest_path (d);
+ ASSERT_EQ (path_to_d.m_edges.length (), 0); /* No path. */
+
+ test_path path_to_e = sp.get_shortest_path (e);
+ ASSERT_EQ (path_to_e.m_edges.length (), 1);
+ ASSERT_EQ (path_to_e.m_edges[0], ef);
+
+ test_path path_to_f = sp.get_shortest_path (f);
+ ASSERT_EQ (path_to_f.m_edges.length (), 0);
+ }
}
/* Run all of the selftests within this file. */
@@ -23,8 +23,24 @@ along with GCC; see the file COPYING3. If not see
#include "timevar.h"
-/* A record of the shortest path to each node in an graph
- from the origin node.
+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. */
@@ -37,35 +53,46 @@ public:
typedef typename GraphTraits::edge_t edge_t;
typedef Path_t path_t;
- shortest_paths (const graph_t &graph, const node_t *origin);
+ shortest_paths (const graph_t &graph, const node_t *given_node,
+ enum shortest_path_sense sense);
- path_t get_shortest_path (const node_t *to) const;
+ path_t get_shortest_path (const node_t *other_node) const;
private:
const graph_t &m_graph;
- /* For each node (by index), the minimal distance to that node from the
- origin. */
+ 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 exploded_node (by index), the previous edge in the shortest
- path from the origin. */
- auto_vec<const edge_t *> m_prev;
+ /* 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 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. */
+ 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 *origin)
+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_prev (graph.m_nodes.length ())
+ m_best_edge (graph.m_nodes.length ())
{
auto_timevar tv (TV_ANALYZER_SHORTEST_PATHS);
@@ -74,10 +101,10 @@ shortest_paths<GraphTraits, Path_t>::shortest_paths (const graph_t &graph,
for (unsigned i = 0; i < graph.m_nodes.length (); i++)
{
m_dist.quick_push (INT_MAX);
- m_prev.quick_push (NULL);
+ m_best_edge.quick_push (NULL);
queue.quick_push (i);
}
- m_dist[origin->m_index] = 0;
+ m_dist[given_node->m_index] = 0;
while (queue.length () > 0)
{
@@ -107,39 +134,67 @@ shortest_paths<GraphTraits, Path_t>::shortest_paths (const graph_t &graph,
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)
+ if (m_sense == SPS_FROM_GIVEN_ORIGIN)
{
- // 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])
+ int i;
+ edge_t *succ;
+ FOR_EACH_VEC_ELT (n->m_succs, i, succ)
{
- m_dist[dest->m_index] = alt;
- m_prev[dest->m_index] = 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 to the node
- TO from the origin node.
+/* 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 *to) const
+shortest_paths<GraphTraits, Path_t>::
+get_shortest_path (const node_t *other_node) const
{
Path_t result;
- while (m_prev[to->m_index])
+ while (m_best_edge[other_node->m_index])
{
- result.m_edges.safe_push (m_prev[to->m_index]);
- to = m_prev[to->m_index]->m_src;
+ 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;
}
- result.m_edges.reverse ();
+ if (m_sense == SPS_FROM_GIVEN_ORIGIN)
+ result.m_edges.reverse ();
return result;
}