Thesis » QuynhNguyen-MS

# Implement the section IV in Puzis 2012 paper

# straight_lineent the section IV in Puzis 2012 paper

# Heuristic Betweenness Centrality - Partitioning to Bi-connected Components

import os

import sys

import pprint

import networkx as nx

import betweenness_centrality as centrality

import utility

from pdb import set_trace as debugger

MAIN_CODE_DIR = os.environ.get('MAIN_CODE_DIR', '')

class HeuristicBetweennessCentrality():

    def __init__(self, graph):

        if not nx.is_connected(graph):

            print "Graph is not connected"

            sys.exit()

        else:

            print "Graph is connected"

        subgraphs, bicomponents, cutpoints, num_vertices, link_weight, traffic_matrix):

        self.subgraphs = list(nx.biconnected_component_subgraphs(graph))

        self.bicomponents = list(nx.biconnected_components(graph))

        self.cutpoints = set(nx.articulation_points(graph))

        self.num_vertices = nx.number_of_nodes(graph)

        self.link_weight = LinkWeight(graph, bicomponents, cutpoints)

        self.traffic_matrix = LinkWeight(graph, bicomponents, cutpoints)RR

        self.bc_components = list()

        self.calculate_bc_non_cutpoint()

        self.calculate_bc_cutpoint()

        self.bc = dict()

        self.finalize()

    def calculate_bc_non_cutpoint(self):

        """BC for non cutpoint

        """

        for i, subgraph in enumerate(self.subgraphs):

            traffic_matrix = self.traffic_matrix[i]

            cut_without = self.num_vertices - nx.number_of_nodes(subgraph)

            results = centrality.weight_betweenness_centrality(subgraph, traffic_matrix, cut_without)

            self.bc_components.append(results)

    def calculate_bc_cutpoint(self):

        self.bc_cutpoints = dict()

        bc_inter = dict()

        for v in self.cutpoints:

            inter = 0

            for i, comp in enumerate(self.bicomponents):

                if v in comp:

                    inter += self.link_weight.get_link_weight(i, v

                        ) * self.link_weight.get_reverse_link_weight(i, v)

            bc_inter[v] = inter

        print 'XXXX bc_components = %s' % self.bc_components

        print 'XXXX inter = %s' % bc_inter

        for v in self.cutpoints:

            bc_locally = 0

            for i, comp in enumerate(self.bicomponents):

                if v in comp:

                    bc_locally += self.bc_components[i][v]

            self.bc_cutpoints[v] = bc_locally - bc_inter[v]

            # TODO: do not minus the bc_inter

            # self.bc_cutpoints[v] = bc_locally

    def finalize(self):

        # Add the bc for non cutpoint vertices

        for bc_component in self.bc_components:

            for key, value in bc_component.iteritems():

                if key not in self.bc:

                    self.bc[key] = value

        # Add the bc for cutpoint vertices

        for key, value in self.bc_cutpoints.iteritems():

            self.bc[key] = value

        # Rescale the bc according to the original graph

        factor = 1.0 / ((self.num_vertices - 1) * (self.num_vertices - 2))

        # TODO: check the scaling factor, how much should it be?

        # factor = 2.0 / (self.num_vertices*self.num_vertices - 3 * self.num_vertices + 2)

        for key, value in self.bc.iteritems():

            self.bc[key] = value * factor

    def write(self, file_suffix=''):

        filepath = '/output/heuristic_%s.csv'  % file_suffix

        with open(MAIN_CODE_DIR + filepath, 'w') as output:

            for node, centrality in self.bc.iteritems():

                output.write('%s, %s\n' % (node, centrality))

    def __str__(self):

        return str(self.bc)

class TrafficMatrix():

    def __init__(self, bicomponents, cutpoints, link_weight):

        self.bicomponents = bicomponents

        self.cutpoints = cutpoints

        self.num_components = len(bicomponents)

        self.link_weight = link_weight

        self.h = list()

        self.generate_empty_traffic_matrix()

        self.generate_traffic_matrix()

    def generate_empty_traffic_matrix(self):

        for i in range(self.num_components):

            l = len(self.bicomponents[i])

            matrix = [[1 for x in range(l)] for y in range(l)]

            # update the main diagonal

            for x in range(l):

                matrix[x][x] = 0

            self.h.append(matrix)

    def generate_traffic_matrix(self):

        # Update the value when one vertex is a cut-point, another vertex is not a cut-point

        for i, components in enumerate(self.bicomponents):

            normal_points = components.difference(self.cutpoints)

            cutpoints = self.cutpoints.intersection(components)

            for cutpoint in cutpoints:

                for normal_point in normal_points:

                    communication_intensity = self.link_weight.get_reverse_link_weight(i, cutpoint) + 1

                    self.update(i, cutpoint, normal_point, communication_intensity)

        # Update the value when both vertices are cut-points

        for i, components in enumerate(self.bicomponents):

            cutpoints = list(self.cutpoints.intersection(components))

            len_cutpoints = len(cutpoints)

            if len_cutpoints > 1:

                for k in range(len_cutpoints - 1):

                    for l in range(1, len_cutpoints):

                        if k == l:

                            continue

                        communication_intensity = (

                            self.link_weight.get_reverse_link_weight(i, cutpoints[k]) + 1) * (

                            self.link_weight.get_reverse_link_weight(i, cutpoints[l]) + 1

                        )

                        self.update(i, cutpoints[k], cutpoints[l], communication_intensity)

    def simple_update(self, comp_index, x_pos, y_pos, value):

        self.h[comp_index][x_pos][y_pos] = value

        # to keep the symmetric property of Traffic Matrix

        self.h[comp_index][y_pos][x_pos] = value

    def update(self, comp_index, x, y, value):

        comp = sorted(self.bicomponents[comp_index])

        try:

            x_pos = list(comp).index(x)

            y_pos = list(comp).index(y)

        except:

            debugger()

            a = 2

        self.simple_update(comp_index, x_pos, y_pos, value)

    def __str__(self):

        return str(self.h)

    def __getitem__(self, key):

        return self.h[key]

class LinkWeight():

    def __init__(self, graph, bicomponents, cutpoints):

        self.num_vertices = nx.number_of_nodes(graph)

        self.bicomponents = bicomponents

        self.num_components = len(bicomponents)

        self.cutpoints = cutpoints

        self.Dv_B = [dict() for i in range(self.num_components)] # link weight

        self.compute_component_tree_weight()

        self.reverse_Dv_B = [dict() for i in range(self.num_components)] # reverse link weight

        self.generate_reverse_link_weight()

    def _components_sharing_cutpoint(self, B_cutpoints, point):

        indices = list()

        for i, cp in enumerate(B_cutpoints):

            if point in cp:

                indices.append(i)

        return indices

    def get_link_weight(self, comp_index, point):

        Dv_B_comp = self.Dv_B[comp_index]

        if point in Dv_B_comp:

            return Dv_B_comp[point]

        else:

            return 0

    def set_link_weight(self, comp_index, point, value):

        self.Dv_B[comp_index][point] = value

    def get_reverse_link_weight(self, comp_index, point):

        reverse_Dv_B_comp = self.reverse_Dv_B[comp_index]

        if point in reverse_Dv_B_comp:

            return reverse_Dv_B_comp[point]

        else:

            return 0

    def generate_reverse_link_weight(self):

        for i, Dv_B_i in enumerate(self.Dv_B):

            for key, value in Dv_B_i.iteritems():

                self.reverse_Dv_B[i][key] = self.num_vertices - 1 - self.get_link_weight(i, key)

    def compute_component_tree_weight(self):

        """Follows exactly the Algorithm 1 [Puzis 2012]

        """

        B_cutpoints = list() # number of cutpoints in component B

        for comp in self.bicomponents:

            points = comp.intersection(self.cutpoints)

            B_cutpoints.append(points)

        Q = self._inititalize_component_tree_weight()

        while Q:

            pair = Q.pop(0)

            if pair['type'] == 'component_vertex_pair':

                B_index = pair['value'][0]

                v = pair['value'][1]

                size = len(self.bicomponents[B_index]) - 1;

                all_cutpoints = self.bicomponents[B_index].intersection(self.cutpoints)

                all_cutpoints.remove(v)

                for cp in all_cutpoints:

                    if self.get_link_weight(B_index, cp) != -1:

                        size += self.num_vertices - self.get_link_weight(B_index, cp) - 1

                link_weight = size

                self._verify_link_weight(B_index, v, link_weight)

                self.set_link_weight(B_index, v, link_weight)

                # update Q

                Q = self._find_unknown_weight_wrt_cutpoint(v, Q)

            if pair['type'] == 'vertex_component_pair':

                size = 0

                B_index = pair['value'][0]

                v = pair['value'][1]

                shared_comp_indices = self._components_sharing_cutpoint(B_cutpoints, v)

                shared_comp_indices.remove(B_index)

                for i in shared_comp_indices:

                    if self.get_link_weight(i, v) != - 1:

                        size += self.get_link_weight(i, v)

                link_weight = self.num_vertices - 1 - size

                self._verify_link_weight(B_index, v, link_weight)

                self.set_link_weight(B_index, v, link_weight)

                # update Q

                Q = self._find_unknown_weight_wrt_component(B_index, Q)

    def _verify_link_weight(self, B_index, v, value):

        """ If the old_value exist in self.Dv_B, then it must be equal to new value

        Otherwise, do nothing

        """

        old_value = self.get_link_weight(B_index, v)

        if old_value != -1: # -1 is unknown

            if old_value != value:

                print "BUGS FOUND in _verify_link_weight()"

                sys.exit()

    def _inititalize_component_tree_weight(self):

        Q = []

        for i, comp in enumerate(self.bicomponents):

            current_cutpoints = self.cutpoints.intersection(comp)

            if len(current_cutpoints) == 1:

                Q.append({

                    'type': 'component_vertex_pair',

                    'value': (i, list(current_cutpoints)[0]) # (B_i, cutpoint) = (i-th component, the cutpoint name)

                    })

            for cp in current_cutpoints:

                self.set_link_weight(i, cp, -1)

        return Q

    def _find_unknown_weight_wrt_cutpoint(self, cutpoint, Q):

        num_of_uncomputed_weight = 0

        uncomputed_component_index = []

        for i, Dv_B_comp in enumerate(self.Dv_B):

            if cutpoint in Dv_B_comp:

                if Dv_B_comp[cutpoint] == -1:

                    num_of_uncomputed_weight += 1

                    uncomputed_component_index.append(i)

                if num_of_uncomputed_weight > 1:

                    break

        if num_of_uncomputed_weight == 1:

            pair = {

                'type': 'vertex_component_pair',

                'value': (uncomputed_component_index.pop(), cutpoint)

            }

            Q.append(pair)

        return Q

    def _find_unknown_weight_wrt_component(self, comp_index, Q):

        # Component B such that weights of all but one of its links in T are already computed.

        Dv_B_comp = self.Dv_B[comp_index]

        values = Dv_B_comp.values()

        # Check if -1 value appear only 1 time

        flag = False

        minus_one_value = [x for x in values if x == -1]

        if len(minus_one_value) == 1:

            for cp, value in Dv_B_comp.iteritems():

                if value == -1:

                    pair = {

                        'type': 'component_vertex_pair',

                        'value': (comp_index, cp)

                    }

                    Q.append(pair)

        return Q

    def __str__(self):

        return str(self.Dv_B)