55 lines
1.4 KiB
Python
55 lines
1.4 KiB
Python
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from collections import deque, defaultdict
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import logging
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from cfg import config
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logger = logging.getLogger(__name__)
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class DijkstraHelper(object):
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def __init__(self, nodes, connections):
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self._nodes = {node: float("inf") for node in nodes}
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self._connections = connections
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self._todo_in_next_step = set()
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@classmethod
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def from_db(cls, connection):
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cursor = connection.cursor()
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cursor.execute("SELECT page_id FROM pages")
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nodes = [n[0] for n in cursor.fetchall()]
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connections = defaultdict(list)
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cursor.execute("SELECT source, destination FROM links")
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for source, destination in cursor:
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connections[source].append(destination)
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return cls(nodes, connections)
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def dijkstra(self, root):
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self.recursive_dijkstra([root], 0)
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def recursive_dijkstra(self, todos, depth):
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if(not todos):
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return
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logger.info("recursive_dijkstra(<{} nodes>, {})".format(len(todos), depth))
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next_todos = deque()
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for todo in todos:
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next_todos.extend(self.dijkstra_one(todo, depth))
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self.recursive_dijkstra(next_todos, depth + 1)
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def dijkstra_one(self, node, depth):
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for neighbor in self._connections[node]:
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if(self._nodes[neighbor] <= depth):
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continue
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self._nodes[neighbor] = depth
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yield neighbor
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def write_back(self, connection):
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cursor = connection.cursor()
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cursor.execute("DELETE FROM dijkstra_helper")
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cursor.executemany("INSERT INTO dijkstra_helper(page, value) VALUES(%s, %s)", list(self._nodes.items()))
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