Calculate link utilization given a traffic matrix.
Return a dictionary mapping for each link of a topology, the relative link utilization (i.e. traffic volume divided by link capacity) given a traffic matrix. The keys of the dictionary are (u, v) tuple where u and v are respectively the source and destination nodes of the link. The values are float values between 0 and 1. A zero value means that the link is not utilized, while a one value means that the link is saturated.
Link utilizations are calculated assuming that all traffic is routed following the shortest path from origin to destination, calculated with the Dijkstra algorithm. If the topology is annotated with link weights, they are used for the shortest path calculation. Otherwise hop count is used.
Parameters : | topology : topology
tm : TrafficMatrix
routing_matrix : dict of dicts
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Returns : | link_loads : dict
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