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"""! |
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@brief Graph coloring algorithm: DSATUR |
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@details Based on article description: |
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- D.Brelaz. New Methods to color the vertices of a graph. 1979. |
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@authors Andrei Novikov ([email protected]) |
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@date 2014-2016 |
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@copyright GNU Public License |
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@cond GNU_PUBLIC_LICENSE |
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PyClustering is free software: you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation, either version 3 of the License, or |
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(at your option) any later version. |
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PyClustering is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with this program. If not, see <http://www.gnu.org/licenses/>. |
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@endcond |
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""" |
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class dsatur: |
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"""! |
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@brief Represents DSATUR algorithm for graph coloring problem that uses greedy strategy. |
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""" |
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__data_pointer = None; |
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__coloring = None; |
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def __init__(self, data): |
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"""! |
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@brief Constructor of DSATUR algorithm. |
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@param[in] data (list): Matrix graph representation. |
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""" |
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if (len(data[0]) != len(data)): |
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raise NameError('Only matrix graph representation is available.'); |
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self.__data_pointer = data; |
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self.__colors = []; |
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def process(self): |
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"""! |
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@brief Perform graph coloring using DSATUR algorithm. |
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@see get_colors() |
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""" |
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color_counter = 1; |
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degrees = list(); |
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saturation_degrees = [0] * len(self.__data_pointer); |
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self.__coloring = [0] * len(self.__data_pointer); |
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uncolored_vertices = set(range(len(self.__data_pointer))); |
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index_maximum_degree = 0; |
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maximum_degree = 0; |
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for index_node in range(len(self.__data_pointer)): |
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# Fill degree of nodes in the input graph |
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degrees.append( ( sum(self.__data_pointer[index_node]), index_node ) ); |
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# And find node with maximal degree at the same time. |
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if (degrees[index_node][0] > maximum_degree): |
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(maximum_degree, node_index) = degrees[index_node]; |
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index_maximum_degree = index_node; |
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# Update saturation |
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neighbors = self.__get_neighbors(index_maximum_degree); |
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for index_neighbor in neighbors: |
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saturation_degrees[index_neighbor] += 1; |
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# Coloring the first node |
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self.__coloring[index_maximum_degree] = color_counter; |
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uncolored_vertices.remove(index_maximum_degree); |
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while(len(uncolored_vertices) > 0): |
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# Get maximum saturation degree |
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maximum_satur_degree = -1; |
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for index in uncolored_vertices: |
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if (saturation_degrees[index] > maximum_satur_degree): |
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maximum_satur_degree = saturation_degrees[index]; |
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# Get list of indexes with maximum saturation degree |
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indexes_maximum_satur_degree = [index for index in uncolored_vertices if saturation_degrees[index] == maximum_satur_degree]; |
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coloring_index = indexes_maximum_satur_degree[0]; |
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if (len(indexes_maximum_satur_degree) > 1): # There are more then one node with maximum saturation |
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# Find node with maximum degree |
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maximum_degree = -1; |
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for index in indexes_maximum_satur_degree: |
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(degree, node_index) = degrees[index]; |
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if (degree > maximum_degree): |
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coloring_index = node_index; |
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maximum_degree = degree; |
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# Coloring |
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node_index_neighbors = self.__get_neighbors(coloring_index); |
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for number_color in range(1, color_counter + 1, 1): |
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if (self.__get_amount_color(node_index_neighbors, number_color) == 0): |
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self.__coloring[coloring_index] = number_color; |
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break; |
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# If it has not been colored then |
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if (self.__coloring[coloring_index] == 0): |
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color_counter += 1; # Add new color |
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self.__coloring[coloring_index] = color_counter; |
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# Remove node from uncolored set |
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uncolored_vertices.remove(coloring_index); |
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# Update degree of saturation |
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for index_neighbor in node_index_neighbors: |
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subneighbors = self.__get_neighbors(index_neighbor); |
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if (self.__get_amount_color(subneighbors, self.__coloring[coloring_index]) == 1): |
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saturation_degrees[index_neighbor] += 1; |
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def get_colors(self): |
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"""! |
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@brief Returns results of graph coloring. |
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@return (list) list with assigned colors where each element corresponds |
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to node in the graph, for example [1, 2, 2, 1, 3, 4, 1]. |
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@see process() |
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""" |
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return self.__coloring; |
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def __get_amount_color(self, node_indexes, color_number): |
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"""! |
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@brief Countes how many nodes has color 'color_number'. |
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@param[in] node_indexes (list): Indexes of graph nodes for checking. |
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@param[in] color_number (uint): Number of color that is searched in nodes. |
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@return (uint) Number found nodes with the specified color 'color_number'. |
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""" |
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color_counter = 0; |
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for index in node_indexes: |
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if (self.__coloring[index] == color_number): |
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color_counter += 1; |
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return color_counter; |
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def __get_neighbors(self, node_index): |
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"""! |
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@brief Returns indexes of neighbors of the specified node. |
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@param[in] node_index (uint): |
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@return (list) Neighbors of the specified node. |
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""" |
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return [ index for index in range(len(self.__data_pointer[node_index])) if self.__data_pointer[node_index][index] != 0 ]; |
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annoviko /
pyclustering
