# # / /
# # c -3- d -8- e
# #
-# var graph = new Graph[Node,WeigthedLink[Node]]
+# var graph = new Graph[Node,WeightedLink]
#
# var na = new Node(graph)
# var nb = new Node(graph)
# ~~~
module a_star
-redef class Object
- protected fun debug_a_star: Bool do return false
- private fun debug(msg: String) do if debug_a_star then
- stderr.write "a_star debug: {msg}\n"
- end
-end
-
# General graph node
class Node
type N: Node
# parent graph
var graph: Graph[N, Link]
- init(graph: Graph[N, Link])
+ init
do
- self.graph = graph
graph.add_node(self)
end
private var last_pathfinding_evocation: Int = 0
# cost up to in current evocation
- # lifetime limited to evocation of path_to
+ # lifetime limited to evocation of `path_to`
private var best_cost_up_to: Int = 0
# source node
- # lifetime limited to evocation of path_to
+ # lifetime limited to evocation of `path_to`
private var best_source: nullable N = null
# is in frontier or buckets
- # lifetime limited to evocation of path_to
+ # lifetime limited to evocation of `path_to`
private var open: Bool = false
-
# Main functionnality, returns path from `self` to `dest`
fun path_to(dest: N, max_cost: Int, context: PathContext): nullable Path[N]
do
+ return path_to_alts(dest, max_cost, context, null)
+ end
+
+ # Find a path to a possible `destination` or a node accepted by `alt_targets`
+ fun path_to_alts(destination: nullable N, max_cost: Int, context: PathContext,
+ alt_targets: nullable TargetCondition[N]): nullable Path[N]
+ do
var cost = 0
var nbr_buckets = context.worst_cost + context.worst_heuristic_cost + 1
var current_bucket = buckets[cost % nbr_buckets]
if current_bucket.is_empty then # move to next bucket
- debug "b {cost} {cost % nbr_buckets} {buckets[cost % nbr_buckets].hash}"
cost += 1
if cost > max_cost then return null
bucket_searched += 1
if bucket_searched > nbr_buckets then break
else # found a node
- debug "c {cost}"
frontier_node = current_bucket.pop
if frontier_node.open then break
return null
# at destination
- else if frontier_node == dest then
- debug "picked {frontier_node}, is destination"
+ else if frontier_node == destination or
+ (alt_targets != null and alt_targets.accept(frontier_node)) then
var path = new Path[N](cost)
else
frontier_node.open = false
- debug "w exploring adjacents of {frontier_node}"
-
for link in frontier_node.links do
var peek_node = link.to
- debug "v {context.is_blocked(link)} {peek_node.last_pathfinding_evocation != graph.pathfinding_current_evocation} {peek_node.best_cost_up_to > frontier_node.best_cost_up_to + context.cost(link)}, {peek_node.best_cost_up_to} > {frontier_node.best_cost_up_to} + {context.cost(link)}"
if not context.is_blocked(link) and
(peek_node.last_pathfinding_evocation != graph.pathfinding_current_evocation or
(peek_node.open and
peek_node.best_cost_up_to > cost + context.cost(link)))
then
-
peek_node.open = true
peek_node.last_pathfinding_evocation = graph.pathfinding_current_evocation
peek_node.best_cost_up_to = cost + context.cost(link)
peek_node.best_source = frontier_node
- var est_cost = peek_node.best_cost_up_to+context.heuristic_cost(link.from, peek_node)
+ var est_cost
+ if destination != null then
+ est_cost = peek_node.best_cost_up_to + context.heuristic_cost(peek_node, destination)
+ else if alt_targets != null then
+ est_cost = peek_node.best_cost_up_to + alt_targets.heuristic_cost(peek_node, link)
+ else est_cost = 0
+
var at_bucket = buckets[est_cost % nbr_buckets]
at_bucket.add(peek_node)
-
- debug "u putting {peek_node} at {est_cost} -> {est_cost % nbr_buckets} {at_bucket.hash}, {cost}+{context.cost(link)}"
end
end
end
var from: N
var to: N
- init(graph: Graph[N, L], from, to: N)
+ init
do
- self.graph = graph
- self.from = from
- self.to = to
-
graph.add_link(self)
end
end
var nodes = new List[N]
- init (cost: Int) do total_cost = cost
var at: Int = 0
fun step: N
redef type L: WeightedLink
- init(graph: Graph[N, L])
+ init
do
super
self.worst_cost = worst_cost
end
- redef var worst_cost: Int
+ redef var worst_cost: Int is noinit
redef fun cost(l) do
return l.weight
var weight: Int
- init(graph: Graph[N, L], from, to: N, weight: Int)
- do
- super
+end
- self.weight = weight
- end
+# Advanced path conditions with customizable accept states
+class TargetCondition[N: Node]
+ # Should the pathfinding accept `node` as a goal?
+ fun accept(node: N): Bool is abstract
+
+ # Approximate cost from `node` to an accept state
+ fun heuristic_cost(node: N, link: Link): Int is abstract
end
nitlanguage / nit.git / blobdiff