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Rename cheapest_score for clarity and add documentation to fields of NodeEntry

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Imbris
2023-04-24 22:42:35 -04:00
parent 87f042eb45
commit 29f0f0d83f
1 changed files with 20 additions and 13 deletions
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33
common/src/astar.rs
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@ -85,9 +85,16 @@ impl<T> PathResult<T> {
// If node entry exists, this was visited! // If node entry exists, this was visited!
#[derive(Clone, Debug)] #[derive(Clone, Debug)]
struct NodeEntry<S> { struct NodeEntry<S> {
// if came_from == self this is the start node! /// Previous node in the cheapest path (known so far) that goes from the
/// start to this node.
///
/// If `came_from == self` this is the start node! (to avoid inflating the
/// size with `Option`)
came_from: S, came_from: S,
cheapest_score: f32, /// Cost to reach this node from the start by following the cheapest path
/// known so far. This is the sum of the transition costs between all the
/// nodes on this path.
cost: f32,
} }
#[derive(Clone)] #[derive(Clone)]
@ -131,7 +138,7 @@ impl<S: Clone + Eq + Hash, H: BuildHasher + Clone> Astar<S, H> {
let mut s = HashMap::with_capacity_and_hasher(1, hasher); let mut s = HashMap::with_capacity_and_hasher(1, hasher);
s.extend(core::iter::once((start.clone(), NodeEntry { s.extend(core::iter::once((start.clone(), NodeEntry {
came_from: start, came_from: start,
cheapest_score: 0.0, cost: 0.0,
}))); })));
s s
}, },
@ -165,14 +172,14 @@ impl<S: Clone + Eq + Hash, H: BuildHasher + Clone> Astar<S, H> {
cost_estimate, cost_estimate,
}) = self.potential_nodes.pop() }) = self.potential_nodes.pop()
{ {
let (node_cheapest, came_from) = self let (node_cost, came_from) = self
.visited_nodes .visited_nodes
.get(&node) .get(&node)
.map(|n| (n.cheapest_score, n.came_from.clone())) .map(|n| (n.cost, n.came_from.clone()))
.expect("All nodes in the queue should be included in visisted_nodes"); .expect("All nodes in the queue should be included in visisted_nodes");
if satisfied(&node) { if satisfied(&node) {
return PathResult::Path(self.reconstruct_path_to(node), node_cheapest); return PathResult::Path(self.reconstruct_path_to(node), node_cost);
// Note, we assume that cost_estimate isn't an overestimation // Note, we assume that cost_estimate isn't an overestimation
// (i.e. that `heuristic` doesn't overestimate). // (i.e. that `heuristic` doesn't overestimate).
} else if cost_estimate > self.max_cost { } else if cost_estimate > self.max_cost {
@ -183,28 +190,28 @@ impl<S: Clone + Eq + Hash, H: BuildHasher + Clone> Astar<S, H> {
.unwrap_or_default(), .unwrap_or_default(),
); );
} else { } else {
for (neighbor, transition) in neighbors(&node) { for (neighbor, transition_cost) in neighbors(&node) {
if neighbor == came_from { if neighbor == came_from {
continue; continue;
} }
let neighbor_cheapest = self let neighbor_cost = self
.visited_nodes .visited_nodes
.get(&neighbor) .get(&neighbor)
.map_or(f32::MAX, |n| n.cheapest_score); .map_or(f32::MAX, |n| n.cost);
// compute cost to traverse to each neighbor // compute cost to traverse to each neighbor
let cost = node_cheapest + transition; let cost = node_cost + transition_cost;
if cost < neighbor_cheapest { if cost < neighbor_cost {
let previously_visited = self let previously_visited = self
.visited_nodes .visited_nodes
.insert(neighbor.clone(), NodeEntry { .insert(neighbor.clone(), NodeEntry {
came_from: node.clone(), came_from: node.clone(),
cheapest_score: cost, cost,
}) })
.is_some(); .is_some();
let h = heuristic(&neighbor, &node); let h = heuristic(&neighbor, &node);
// note that cheapest_score does not include the heuristic // note that `cost` field does not include the heuristic
// priority queue does include heuristic // priority queue does include heuristic
let cost_estimate = cost + h; let cost_estimate = cost + h;