/**
* @param Vertex $vertex
* @return Walk
*/
protected function getWalkForVertex(Vertex $vertex)
{
if ($vertex->getId() == $this->graph->getRoot()) {
return Walk::factoryFromEdges([], $vertex);
} else {
$shortestPath = new BreadthFirst($vertex);
return $shortestPath->getWalkTo($this->vertices->getVertexLast());
}
}
/**
* Returns max flow graph
*
* @return Graph
*/
public function createGraph()
{
$graphResult = $this->startVertex->getGraph()->createGraphClone();
// initialize null flow and check edges
foreach ($graphResult->getEdges() as $edge) {
if (!$edge instanceof EdgeDirected) {
throw new UnexpectedValueException('Undirected edges not supported for edmonds karp');
}
$edge->setFlow(0);
}
$idA = $this->startVertex->getId();
$idB = $this->destinationVertex->getId();
do {
// Generate new residual graph and repeat
$residualAlgorithm = new ResidualGraph($graphResult);
$graphResidual = $residualAlgorithm->createGraph();
// 1. Search _shortest_ (number of hops and cheapest) path from s -> t
$alg = new BreadthFirst($graphResidual->getVertex($idA));
try {
$pathFlow = $alg->getWalkTo($graphResidual->getVertex($idB));
} catch (OutOfBoundsException $e) {
$pathFlow = NULL;
}
// If path exists add the new flow to graph
if ($pathFlow) {
// 2. get max flow from path
$maxFlowValue = $pathFlow->getEdges()->getEdgeOrder(Edges::ORDER_CAPACITY)->getCapacity();
// 3. add flow to path
foreach ($pathFlow->getEdges() as $edge) {
// try to look for forward edge to increase flow
try {
$originalEdge = $graphResult->getEdgeClone($edge);
$originalEdge->setFlow($originalEdge->getFlow() + $maxFlowValue);
// forward edge not found, look for back edge to decrease flow
} catch (UnderflowException $e) {
$originalEdge = $graphResult->getEdgeCloneInverted($edge);
$originalEdge->setFlow($originalEdge->getFlow() - $maxFlowValue);
}
}
}
// repeat while we still finds paths with residual capacity to add flow to
} while ($pathFlow);
return $graphResult;
}
/**
* Find shortest path between versions
*
* @param string $fromClassName
* @param string $toClassName
*
* @return MethodInfo[]
*/
public function find($fromClassName, $toClassName)
{
$annotations = array();
$graph = new Graph();
$this->createEdges($graph, $fromClassName);
$this->createEdges($graph, $toClassName);
try {
$breadFirst = new BreadthFirst($graph->getVertex($fromClassName));
$edges = $breadFirst->getEdgesTo($graph->getVertex($toClassName));
/** @var Directed $edge */
foreach ($edges as $edge) {
$annotations[] = $this->annotations[$this->getEdgeId($edge)];
}
} catch (OutOfBoundsException $e) {
return null;
}
return $annotations;
}
