* reference to that node by the edge callback for *any* node and
* index MUST use the same pointer.
*
+ * - The ei->icost field MAY be set by the edge_info callback to
+ * indicate the edge's cost / length represented as an integer (of
+ * type aga_icost_t), Otherwise the cost defaults to 1.
+ *
* Concurrency
* ===========
*
#include <ccan/check_type/check_type.h>
#include <ccan/lstack/lstack.h>
#include <ccan/lqueue/lqueue.h>
+#include <ccan/lpq/lpq.h>
struct aga_graph;
struct aga_node;
const struct aga_node *n,
const void *e);
+typedef long aga_icost_t;
+
struct aga_edge_info {
struct aga_node *to;
+ aga_icost_t icost; /* integer edge cost */
};
+
typedef int (*aga_edge_info_fn)(const struct aga_graph *g,
const struct aga_node *n,
const void *e, struct aga_edge_info *ei);
struct lqueue_link next;
const void *edge;
} bfs;
+ struct {
+ aga_icost_t distance;
+ struct aga_node *prev;
+ const void *prevedge;
+ bool complete;
+ struct lpq_link pqlink;
+ } dijkstra;
+ struct {
+ aga_icost_t distance;
+ struct aga_node *prev;
+ const void *prevedge;
+ struct aga_node *list;
+ } bellman_ford;
} u;
};
aga_first_edge_fn first_edge;
aga_next_edge_fn next_edge;
aga_edge_info_fn edge_info;
+ union {
+ LPQ(struct aga_node, u.dijkstra.pqlink) dijkstra;
+ struct {
+ struct aga_node *nodelist;
+ int nnodes;
+ int npasses;
+ } bellman_ford;
+ } state;
};
/*
(aga_edge_info_fn)(eifn_)); \
} while (0)
+/**
+ * enum aga_error - Error codes for aga routines
+ *
+ * These error codes are returned by aga_error() for errors detected
+ * within aga itself (rather than errors reported by supplied
+ * callbacks, which should be negative
+ */
+enum aga_error {
+ /* No error */
+ AGA_ERR_NONE = 0,
+ /* Negative edge cost (in a context where it's not valid) */
+ AGA_ERR_NEGATIVE_COST = 1,
+};
+
/**
* aga_error - Determine error state of a graph
* @g: the graph
*
* Performs a breadth first search. The block following this macro is
* executed with @_n set first to @_start, then to each node reachable
- * from @_start in depth first search order.
+ * from @_start in breadth-first search order.
*
* aga_bfs_start() must be called before this macro is used.
*/
#define aga_bfs(_n, _g, _start) \
for ((_n) = (_start) ; ((_n) = aga_bfs_explore((_g), (_n))) != NULL; )
+/*
+ * Dijkstra's algorithm
+ */
+
+/**
+ * aga_dijkstra_start - Start Dijkstra's algorithm
+ * @g: graph
+ * @source: source node
+ *
+ * Start's Dijkstra's algorithm on @g to find shortest paths from node
+ * @source, to other nodes in @g.
+ */
+int aga_dijkstra_start(struct aga_graph *g, struct aga_node *source);
+
+
+/**
+ * aga_dijkstra_step - Find the node with the next shortest path
+ * @g: graph
+ *
+ * The first call to this function returns the source node specified
+ * in aga_dijkstra_start(). Subsequent calls return the next closest
+ * node to source by shortest path cost. Returns NULL if no further
+ * nodes are reachable from source.
+ */
+struct aga_node *aga_dijkstra_step(struct aga_graph *g);
+
+/**
+ * aga_dijkstra_path - Find the shortest path to a node
+ * @g: graph
+ * @dest: destination node
+ * @prev: Second last node in the path *output)
+ * @prevedge: Last edge in the path
+ *
+ * Finds the shortest path from the source node (specified in
+ * aga_dijkstra_start() to @dest using Dijkstra's algorithm.
+ *
+ * If no path exists, return false.
+ *
+ * If a path does exist, returns true. Additionally if @total_cost is
+ * non-NULL, store the total cost of the path in *@total_cost, if
+ * @prev is non-NULL, store the node in the path immediately before
+ * @dest in *@prev and if @prevedge is non-NULL stores the edge which
+ * leads from *@prev to @dest in *@prevedge.
+ *
+ * If @dest is the same as source, 0 will be stored in @cost, and NULL
+ * will be stored in *@prev and *@prevedge.
+ *
+ * The full path from source to @dest can be determined by repeatedly
+ * calling aga_dijkstra_path() on *@prev.
+ *
+ * NOTE: Dijkstra's algorithm will not work correctly on a graph which
+ * has negative costs on some edges. If aga detects this case, it
+ * will set aga_error() to AGA_ERR_NEGATIVE_COST. However,
+ * aga_dijkstra_path() may produce incorrect results without detecting
+ * this situation. aga_dijkstra_all_paths() *is* guaranteed to
+ * discover any negative cost edge reachable from the starting node.
+ */
+bool aga_dijkstra_path(struct aga_graph *g, struct aga_node *dest,
+ aga_icost_t *total_cost,
+ struct aga_node **prev, const void **prevedge);
+
+/**
+ * aga_dijkstra_complete - Find shortest paths to all reachable nodes
+ * @g: graph
+ *
+ * Finds shortest paths from the source node (specified in
+ * aga_dijkstra_start()) to all other reachable nodes in @g. No
+ * results are returned directly, but between calling
+ * aga_dijkstra_all_paths() and aga_finish(), aga_dijkstra_path() is
+ * guaranteed to complete in O(1) time for all destinations.
+ */
+void aga_dijkstra_complete(struct aga_graph *g);
+
+/*
+ * Bellman-Ford algorithm
+ */
+
+/**
+ * aga_bellman_ford_start - Start Bellman-Ford algorithm
+ * @g: graph
+ * @source: source node
+ *
+ * Start's the Bellman-Ford algorithm on @g to find shortest paths
+ * from node @source, to other nodes in @g.
+ */
+int aga_bellman_ford_start(struct aga_graph *g, struct aga_node *source);
+
+/**
+ * aga_bellman_ford_path - Find the shortest path to a node
+ * @g: graph
+ * @dest: destination node
+ * @prev: Second last node in the path *output)
+ * @prevedge: Last edge in the path
+ *
+ * Finds the shortest path from the source node (specified in
+ * aga_bellman_ford_start() to @dest using Bellman_Ford's algorithm.
+ *
+ * If no path exists, return false.
+ *
+ * If a path does exist, returns true. Additionally if @total_cost is
+ * non-NULL, store the total cost of the path in *@total_cost, if
+ * @prev is non-NULL, store the node in the path immediately before
+ * @dest in *@prev and if @prevedge is non-NULL stores the edge which
+ * leads from *@prev to @dest in *@prevedge.
+ *
+ * If @dest is the same as source, 0 will be stored in @cost, and NULL
+ * will be stored in *@prev and *@prevedge.
+ *
+ * The full path from source to @dest can be determined by repeatedly
+ * calling aga_bellman_ford_path() on *@prev.
+ *
+ * NOTE: Bellman_Ford's algorithm will not work correctly on a graph
+ * which contains a cycle with (total) negative cost. If aga detects
+ * this case, it will set aga_error() to AGA_ERR_NEGATIVE_COST.
+ */
+bool aga_bellman_ford_path(struct aga_graph *g, struct aga_node *dest,
+ aga_icost_t *total_cost,
+ struct aga_node **prev, const void **prevedge);
+
+/**
+ * aga_bellman_ford_complete - Run Bellman-Ford algorithm to completion
+ * @g: graph
+ *
+ * Finds shortest paths from the source node (specified in
+ * aga_bellman_ford_start()) to all other reachable nodes in @g. No
+ * results are returned directly, but between calling
+ * aga_bellman_ford_complete() and aga_finish(),
+ * aga_bellman_ford_path() is guaranteed to complete in O(1) time for
+ * all destinations.
+ */
+void aga_bellman_ford_complete(struct aga_graph *g);
+
#endif /* CCAN_AGA_H */
projects / ccan / blobdiff