1. label_prop(1)
  2. www.complex-networks.net
  3. label_prop(1)


label_prop - Find communities using label propagation


label_prop [SYNC|ASYNC] graph_in [max_epochs]


label_prop finds the communities in graph_in using the label propagation algorithm proposed by Raghavan, Albert, and Kumara. The program prints on STDOUT the partition obtained where no more label flips are possible, and reports on STDERR the number of communities and the corresponding value of modularity at each epoch. When used in ASYNC mode, the algorithm is suitable to find communities in large graphs.



The first parameter is used to choose between synchronous (SYNC) or asynchronous (ASYNC) label update.


undirected input graph (edge list). If is equal to - (dash), read the edge list from STDIN.


Sets the maximum number of epochs to run (optional).


The program prints on STDOUT the partition obtained where no more label flips are possible, in the format:

    ## nc: NUM_COMM Q_max: Q_MAX Epochs: EPOCHS
    node_1 comm_1
    node_2 comm_2
    node_3 comm_3

where comm_i is the community to which node_i belongs. The first output line reports the number of communities NUM_COMM, the corresponding value of modularity Q_MAX, and the number of epochs EPOCHS used to find the partition.

The program prints on STDERR the epoch number, the value of modularity of the partition at that epoch, and the number of flips made in that epoch, in the format:

    1 Q_1 flips_1
    2 Q_2 flips_2
    3 Q_3 flips_3

where Q_i is the modularity of the partition at the i-th epoch, and flips_i is the number of label flips performed during that epoch.


We can use label_prop to find communities in the graph karate_club_unweighted.net (Zachary Karate Club network) with the command:

    $ label_prop ASYNC karate_club_unweighted.net 2> karate_label-prop_trace
    ### nc: 2 Q_max: 0.371795 Epochs: 6
    0 0
    1 0
    2 0
    3 0
    30 1
    31 1
    32 1
    33 1

The program has found a partition with 2 communities corrisponding to a modularity Q=0.371795. Notice that node 0, 1, 2, 3, are in community 0, while node 30, 31, 32, 33 are in community 1. In this example, we have chosen to save the information about the modularity and number of flips at each epoch in the file karate_label-prop_trace.


modularity(1), gn(1), cnm(1)



(c) Vincenzo 'KatolaZ' Nicosia 2009-2017 <v.nicosia@qmul.ac.uk>.

  1. www.complex-networks.net
  2. September 2017
  3. label_prop(1)