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A* node: use dataclass (ruff) #281

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Merged
inducer merged 1 commit into from
Jan 9, 2025
Merged

A* node: use dataclass (ruff) #281

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21 changes: 10 additions & 11 deletions pytools/graph.py
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,13 @@ def reverse_graph(graph: GraphT[NodeT]) -> GraphT[NodeT]:

# {{{ a_star

@dataclass(frozen=True)
class _AStarNode(Generic[NodeT]):
state: NodeT
parent: _AStarNode[NodeT] | None
path_cost: float | int


def a_star(
initial_state: NodeT, goal_state: NodeT, neighbor_map: GraphT[NodeT],
estimate_remaining_cost: Callable[[NodeT], float] | None = None,
Expand All @@ -135,19 +142,11 @@ def estimate_remaining_cost(x: NodeT) -> float:
return 1
return 0

class AStarNode:
__slots__ = ["parent", "path_cost", "state"]

def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:
self.state = state
self.parent = parent
self.path_cost = path_cost

inf = float("inf")
init_remcost = estimate_remaining_cost(initial_state)
assert init_remcost != inf

queue = [(init_remcost, AStarNode(initial_state, parent=None, path_cost=0))]
queue = [(init_remcost, _AStarNode(initial_state, parent=None, path_cost=0))]
visited_states = set()

while queue:
Expand All @@ -156,7 +155,7 @@ def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:

if top.state == goal_state:
result = []
it: AStarNode | None = top
it: _AStarNode[NodeT] | None = top
while it is not None:
result.append(it.state)
it = it.parent
Expand All @@ -174,7 +173,7 @@ def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:
estimated_path_cost = top.path_cost+step_cost+remaining_cost
heappush(queue,
(estimated_path_cost,
AStarNode(state, top, path_cost=top.path_cost + step_cost)))
_AStarNode(state, top, path_cost=top.path_cost + step_cost)))

raise RuntimeError("no solution")

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