Merge pull request #13 from CSHVienna/no_pa

TCH model of Triadic Closure & Homophily without Preferential Attachment

netin/generators/__init__.py

@@ -9,5 +9,6 @@
 from .pah import PAH
 from .patc import PATC
 from .patch import PATCH
+from .tch import TCH
 from .tc import TriadicClosure
 from .undirected import UnDiGraph

netin/generators/tch.py

@@ -0,0 +1,185 @@
+from typing import Set, Union, Tuple
+
+import numpy as np
+
+from netin.generators.undirected import UnDiGraph
+from netin.generators.h import Homophily
+from netin.generators.tc import TriadicClosure
+from netin.utils import constants as const
+
+
+class TCH(UnDiGraph, Homophily, TriadicClosure):
+    """Creates a new TCH graph. An undirected graph with homophily and triadic closure as link formation mechanisms.
+
+    Parameters
+    ----------
+    n: int
+        number of nodes (minimum=2)
+
+    k: int
+        minimum degree of nodes (minimum=1)
+
+    f_m: float
+        fraction of minorities (minimum=1/n, maximum=(n-1)/n)
+
+    h_MM: float
+        homophily (similarity) between majority nodes (minimum=0, maximum=1.)
+
+    h_mm: float
+        homophily (similarity) between minority nodes (minimum=0, maximum=1.)
+
+    tc: float
+        probability of a new edge to close a triad (minimum=0, maximum=1.)
+
+    Notes
+    -----
+    The initialization is an undirected graph with n nodes and no edges.
+    Then, everytime a node is selected as source, it gets connected to k target nodes.
+    Target nodes are selected via homophily (h_**; see :class:`netin.Homophily`) [Karimi2018]_ with probability ``1-p_{TC}``,
+    and with probability ``p_{TC}`` via triadic closure (see :class:`netin.TriadicClosure`) [HolmeKim2002]_.
+
+    Note that this model is still work in progress and not fully implemented yet.
+    """
+
+    ############################################################
+    # Constructor
+    ############################################################
+
+    def __init__(self, n: int, k: int, f_m: float, h_mm: float, h_MM: float, tc: float, seed: object = None):
+        UnDiGraph.__init__(self, n, k, f_m, seed)
+        Homophily.__init__(self, n=n, f_m=f_m, h_MM=h_MM, h_mm=h_mm, seed=seed)
+        TriadicClosure.__init__(self, n=n, f_m=f_m, tc=tc, seed=seed)
+
+    ############################################################
+    # Init
+    ############################################################
+
+    def _infer_model_name(self):
+        """
+        Infers the name of the model.
+        """
+        return self.set_model_name(const.TCH_MODEL_NAME)
+
+    ############################################################
+    # Generation
+    ############################################################
+
+    def get_target_probabilities(self, source: Union[None, int], target_set: Union[None, Set[int]],
+                                 special_targets: Union[None, object, iter] = None) -> Tuple[np.array, set[int]]:
+        """
+        Returns the probabilities of nodes to be selected as target nodes.
+
+        Parameters
+        ----------
+        source: int
+            source node id
+
+        target_set: set
+            set of target node ids
+
+        special_targets: dict
+            dictionary of special target node ids to be considered
+
+        Returns
+        -------
+        tuple
+            probabilities of nodes to be selected as target nodes, and set of target of nodes
+
+        """
+        return TriadicClosure.get_target_probabilities(self, source, target_set, special_targets)
+
+    def get_target_probabilities_regular(self, source: Union[None, int], target_set: Union[None, Set[int]],
+                                         special_targets: Union[None, object, iter] = None) -> Tuple[
+        np.ndarray, set[int]]:
+        """
+        Returns the probability of nodes to be selected as target nodes using the homophily mechanism.
+
+        Parameters
+        ----------
+        source: int
+            source node id
+
+        target_set: set
+            set of target node ids
+
+        special_targets: dict
+            dictionary of special target node ids to be considered
+
+        Returns
+        -------
+        tuple
+            probabilities of nodes to be selected as target nodes, and set of target of nodes
+        """
+        probs = np.asarray([self.get_homophily_between_source_and_target(source, target) + const.EPSILON for target in target_set])
+        return probs / probs.sum(), target_set
+
+    def get_special_targets(self, source: int) -> object:
+        """
+        Returns an empty dictionary (source node ids)
+
+        Parameters
+        ----------
+        source : int
+            Newly added node
+
+        Returns
+        -------
+        Dict
+            Empty dictionary
+        """
+        return TriadicClosure.get_special_targets(self, source)
+
+    ############################################################
+    # Calculations
+    ############################################################
+
+    def info_params(self):
+        """
+        Shows the (input) parameters of the graph.
+        """
+        Homophily.info_params(self)
+        TriadicClosure.info_params(self)
+
+    def info_computed(self):
+        """
+        Shows the (computed) properties of the graph.
+        """
+        Homophily.info_computed(self)
+        TriadicClosure.info_computed(self)
+
+    def infer_homophily_values(self) -> Tuple[float, float]:
+        """
+        Infers analytically the homophily values of the graph.
+
+        Returns
+        -------
+        tuple
+            homophily values of the graph (majority, minority)
+        """
+        h_MM = None
+        h_mm = None
+        return h_MM, h_mm
+
+    def infer_triadic_closure(self) -> float:
+        """
+        Infers analytically the triadic closure value of the graph.
+
+        Returns
+        -------
+        float
+            triadic closure probability of the graph
+        """
+        tc = None
+        return tc
+
+    def _makecopy(self):
+        """
+        Makes a copy of the current object.
+        """
+        return self.__class__(n=self.n,
+                              k=self.k,
+                              f_m=self.f_m,
+                              tc=self.tc,
+                              h_MM=self.h_MM,
+                              h_mm=self.h_mm,
+                              seed=self.seed)

netin/utils/constants.py

@@ -35,6 +35,8 @@
 PATC_MODEL_NAME = 'PATC'
 PATCH_MODEL_NAME = 'PATCH'
 
+TCH_MODEL_NAME = 'TCH'
+
 DH_MODEL_NAME = 'DH'
 DPA_MODEL_NAME = 'DPA'
 DPAH_MODEL_NAME = 'DPAH'