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108 lines
2.9 KiB
PHP
108 lines
2.9 KiB
PHP
<?php
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namespace Graphp\Algorithms;
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use Graphp\Algorithms\BaseGraph;
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use Fhaculty\Graph\Edge\Base as Edge;
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use Fhaculty\Graph\Graph;
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/**
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* Basic algorithms for working with the (total) weight of a Graph/Walk
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*
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* A weighted graph associates a label (weight) with every edge in the graph.
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* Sometimes the word cost is used instead of weight. The term network is a
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* synonym for a weighted graph.
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*
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* @link http://en.wikipedia.org/wiki/Glossary_of_graph_theory#Weighted_graphs_and_networks
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*/
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class Weight extends BaseDual
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{
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/**
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* checks whether this graph has any weighted edges
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*
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* edges usually have no weight attached. a weight explicitly set to (int) 0
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* will be considered as 'weighted'.
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*
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* @return boolean
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* @uses Edge::getWeight()
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*/
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public function isWeighted()
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{
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foreach ($this->set->getEdges() as $edge) {
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if ($edge->getWeight() !== NULL) {
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return true;
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}
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}
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return false;
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}
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/**
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* get total weight of graph (sum of weight of all edges)
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*
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* edges with no weight assigned will evaluate to weight (int) 0. thus an
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* unweighted graph (see isWeighted()) will return total weight of (int) 0.
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*
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* returned weight can also be negative or (int) 0 if edges have been
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* assigned a negative weight or a weight of (int) 0.
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*
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* @return float total weight
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* @see self::isWeighted()
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* @uses Edge::getWeight()
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*/
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public function getWeight()
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{
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$weight = 0;
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foreach ($this->set->getEdges() as $edge) {
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$w = $edge->getWeight();
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if ($w !== NULL) {
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$weight += $w;
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}
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}
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return $weight;
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}
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/**
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* get minimum weight assigned to all edges
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*
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* minimum weight is often needed because some algorithms do not support
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* negative weights or edges with zero weight.
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*
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* edges with NO (null) weight will NOT be considered for the minimum weight.
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*
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* @return float|NULL minimum edge weight or NULL if graph is not weighted or empty
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* @uses Edge::getWeight()
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*/
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public function getWeightMin()
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{
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$min = NULL;
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foreach ($this->set->getEdges() as $edge) {
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$weight = $edge->getWeight();
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if ($weight !== null && ($min === NULL || $weight < $min)) {
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$min = $weight;
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}
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}
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return $min;
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}
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/**
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* get total weight of current flow (sum of all edges flow(e) * weight(e))
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*
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* @return float
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* @see Graph::getWeight() to just get the sum of all edges' weights
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* @uses Edge::getFlow()
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* @uses Edge::getWeight()
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*/
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public function getWeightFlow()
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{
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$sum = 0;
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foreach ($this->set->getEdges() as $edge) {
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$sum += $edge->getFlow() * $edge->getWeight();
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}
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return $sum;
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}
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}
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