Dijkstra algorithm optimization/caching

Question

I have the following Dijkstra algorithm with 3 input variables (start, stop and time). It takes about 0.5-1s to complete. My hosting provider says it\'s using too muc

Answer 1

At a glance (you should really do some profiling, by the way), the culprit is the fact that you are executing a query for each graph node to find its neighbors:

$result=mysql_query("SELECT route_id, next_stop FROM db_stop_times WHERE stop_id = $activeNode", $connection);

If you have 1,700 nodes this is going to issue on the order of a thousand queries. Rather than hitting the database so often, cache these database results in something like memcached, and only fall back to the database on cache misses.