|
| 1 | +************************************************** |
| 2 | +Independent Cascades with Community Permeability |
| 3 | +************************************************** |
| 4 | + |
| 5 | +The Independent Cascades with Community Permeability model was introduced by Milli and Rossetti in 2019 [#]_. |
| 6 | + |
| 7 | +This model is a variation of the well-known Independent Cascade (IC), and it is designed to embed community awareness into the IC model. |
| 8 | +This model exploits the idea of permeability. A community is “permeable” to a given content if it permits that content to spread from it fast |
| 9 | +(or vice-versa, if it permits the content to be easily received from nodes outside the community). Conversely, a community has a low degree of permeability if it dampens the diffusion probability across its border. |
| 10 | + |
| 11 | +The ICP model starts with an initial set of **active** nodes A0; the diffusive process unfolds in discrete steps according to the following randomized rule: |
| 12 | + |
| 13 | +- When node v becomes active in step t, it is given a single chance to activate each currently inactive neighbor u. If v and u belong to the same community, the method works as a standard IC model (it succeeds with a probability p(v,u)); instead, if the nodes are part of to different communities, the likelihood p(v,u) is dampened of a factor :math:`\eta` (the community permeability parameter). |
| 14 | +- If u has multiple newly activated neighbors, their attempts are sequenced in an arbitrary order. |
| 15 | +- If v succeeds, then u will become active in step t + 1; but whether or not v succeeds, it cannot make any further attempts to activate u in subsequent rounds. |
| 16 | +- The process runs until no more activations are possible. |
| 17 | + |
| 18 | +-------- |
| 19 | +Statuses |
| 20 | +-------- |
| 21 | + |
| 22 | +During the simulation a node can experience the following statuses: |
| 23 | + |
| 24 | +=========== ==== |
| 25 | +Name Code |
| 26 | +=========== ==== |
| 27 | +Susceptible 0 |
| 28 | +Infected 1 |
| 29 | +Removed 2 |
| 30 | +=========== ==== |
| 31 | + |
| 32 | + |
| 33 | +---------- |
| 34 | +Parameters |
| 35 | +---------- |
| 36 | + |
| 37 | +====================== ===== =============== ======= ========= ====================== |
| 38 | +Name Type Value Type Default Mandatory Description |
| 39 | +====================== ===== =============== ======= ========= ====================== |
| 40 | +Edge threshold Edge float in [0, 1] 0.1 False Edge threshold |
| 41 | +Community permeability Model float in [0, 1] 0.5 True Community Permeability |
| 42 | +====================== ===== =============== ======= ========= ====================== |
| 43 | + |
| 44 | +The initial infection status can be defined via: |
| 45 | + |
| 46 | + - **fraction_infected**: Model Parameter, float in [0, 1] |
| 47 | + - **Infected**: Status Parameter, set of nodes |
| 48 | + |
| 49 | +The two options are mutually exclusive and the latter takes precedence over the former. |
| 50 | + |
| 51 | +------- |
| 52 | +Methods |
| 53 | +------- |
| 54 | + |
| 55 | +The following class methods are made available to configure, describe and execute the simulation: |
| 56 | + |
| 57 | +^^^^^^^^^ |
| 58 | +Configure |
| 59 | +^^^^^^^^^ |
| 60 | + |
| 61 | +.. autoclass:: ndlib.models.epidemics.ICPModel.IndependentCascadesModel |
| 62 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.__init__(graph) |
| 63 | + |
| 64 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.set_initial_status(self, configuration) |
| 65 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.reset(self) |
| 66 | + |
| 67 | +^^^^^^^^ |
| 68 | +Describe |
| 69 | +^^^^^^^^ |
| 70 | + |
| 71 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.get_info(self) |
| 72 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.get_status_map(self) |
| 73 | + |
| 74 | +^^^^^^^^^^^^^^^^^^ |
| 75 | +Execute Simulation |
| 76 | +^^^^^^^^^^^^^^^^^^ |
| 77 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.iteration(self) |
| 78 | +.. automethod:: ndlib.models.epidemics.ICPModel.ICPModel.iteration_bunch(self, bunch_size) |
| 79 | + |
| 80 | +------- |
| 81 | +Example |
| 82 | +------- |
| 83 | + |
| 84 | +In the code below is shown an example of instantiation and execution of an ICP model simulation on a random graph: we set the initial set of infected nodes as 1% of the overall population, assign a threshold of 0.1 to all the edges and set the community permeability equal 0.3. |
| 85 | + |
| 86 | + |
| 87 | +.. code-block:: python |
| 88 | +
|
| 89 | + import networkx as nx |
| 90 | + import ndlib.models.ModelConfig as mc |
| 91 | + import ndlib.models.epidemics as ep |
| 92 | +
|
| 93 | + # Network topology |
| 94 | + g = nx.erdos_renyi_graph(1000, 0.1) |
| 95 | +
|
| 96 | + # Model selection |
| 97 | + model = ep.ICPModel(g) |
| 98 | +
|
| 99 | + # Model Configuration |
| 100 | + config = mc.Configuration() |
| 101 | + config.add_model_parameter('fraction_infected', 0.1) |
| 102 | + config.add_model_parameter('permeability', 0.3) |
| 103 | +
|
| 104 | +
|
| 105 | + # Setting the edge parameters |
| 106 | + threshold = 0.1 |
| 107 | + for e in g.edges(): |
| 108 | + config.add_edge_configuration("threshold", e, threshold) |
| 109 | +
|
| 110 | + model.set_initial_status(config) |
| 111 | +
|
| 112 | + # Simulation execution |
| 113 | + iterations = model.iteration_bunch(200) |
| 114 | +
|
| 115 | +
|
| 116 | +.. [#] L. Milli and G. Rossetti. “Community-Aware Content Diffusion: Embeddednes and Permeability,” in Proceedings of International Conference on Complex Networks and Their Applications, 2019 pp. 362--371. |
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