/**
* Calculate the PageRank for all nodes in $graph.
* @param Graph $graph
* @param bool $keepAllRoundData [optional]. Default: false. If true, the values for every round of calculation is kept. Great for understanding what's going on during the calculation.
* @return PageRankResult
*/
public function calculatePagerank(Graph $graph, $keepAllRoundData = false)
{
$round = 0;
$rounds = [];
$ns = $graph->getNodes();
$edges = $graph->getEdges();
/** @var PageRankNode[] $nodes */
$nodes = [];
//transform to PageRankNodes
foreach ($edges as $edge) {
$prFromNode = $this->getPageRankNode($edge->getFrom(), $nodes);
$prNodeTo = $this->getPageRankNode($edge->getTo(), $nodes);
$prFromNode->addLinkTo($prNodeTo);
$prNodeTo->addLinkFrom($prFromNode);
}
//transform (remaining) disconnected Nodes (that are not part of an Edge) to PageRankNodes
foreach ($ns as $node) {
$this->getPageRankNode($node, $nodes);
}
$this->getLogger()->debug("Got " . count($nodes) . " nodes in total");
do {
$distance = 0;
$currentRound = new PageRankNodeHistory($round);
$newPrCache = [];
foreach ($nodes as $key => $node) {
$node->setOldPr($node->getPr());
$newPr = $node->calculatePageRank($this->dampingFactor, count($nodes));
$curDistance = abs($node->getOldPr() - $newPr);
if ($curDistance > $distance) {
$distance = $curDistance;
}
$entry = new PageRankNodeHistoryEntry($node, $node->getOldPr(), $newPr);
$newPrCache[$key] = $newPr;
$currentRound->addEntry($entry);
}
foreach ($nodes as $key => $node) {
$newPr = $newPrCache[$key];
$node->setPr($newPr);
}
if (!$keepAllRoundData) {
$rounds = [];
}
$rounds[$round] = $currentRound;
$round++;
$this->getLogger()->debug("Calculating round {$round}. Max rounds: {$this->maxRounds}. Last max distance: {$distance}. Required max distance: {$this->maxDistance}");
} while ($round < $this->maxRounds && ($distance == 0 || $distance > $this->maxDistance));
$result = new PageRankResult($graph, $rounds);
return $result;
}
