public function createGraph()
{
$graph = new Graph();
$file = $this->getLines();
$countOfAllVertices = $this->readInt($file[0]);
$countOfVerticesInA = $this->readInt($file[1]);
if ($countOfVerticesInA > $countOfAllVertices || $countOfVerticesInA < 0) {
throw new UnexpectedValueException('Invalid value for number of vertices in group 0');
}
$graph->createVertices($countOfAllVertices);
for ($i = 0; $i < $countOfVerticesInA; ++$i) {
$graph->getVertex($i)->setGroup(0);
}
for ($k = $countOfVerticesInA; $k < $countOfAllVertices; ++$k) {
$graph->getVertex($k)->setGroup(1);
}
unset($file[0]);
unset($file[1]);
foreach ($file as $zeile) {
$parts = $this->readLine($zeile, array('vertex', 'vertex'), $graph);
if ($this->directedEdges) {
$edge = $parts[0]->createEdgeTo($parts[1]);
} else {
$edge = $parts[0]->createEdge($parts[1]);
}
}
$alg = new AlgorithmGroups($graph);
if (!$alg->isBipartit()) {
throw new UnexpectedValueException('Graph read from file does not form a valid bipartit graph');
}
return $graph;
}
public function getEdges()
{
$alg = new Directed($this->graph);
if ($alg->hasDirected()) {
throw new UnexpectedValueException('Input graph contains directed edges');
}
$alg = new Groups($this->graph);
if (!$alg->isBipartit()) {
throw new UnexpectedValueException('Input graph does not have bipartit groups assigned to each vertex. Consider Using "AlgorithmBipartit::createGraph()" first');
}
// create temporary flow graph with supersource and supersink
$graphFlow = $this->graph->createGraphCloneEdgeless();
$superSource = $graphFlow->createVertex()->setLayoutAttribute('label', 's*');
$superSink = $graphFlow->createVertex()->setLayoutAttribute('label', 't*');
$groups = $alg->getGroups();
$groupA = $groups[0];
$groupB = $groups[1];
// connect supersource s* to set A and supersink t* to set B
foreach ($graphFlow->getVertices() as $vertex) {
// we want to skip over supersource & supersink as they do not have a partition assigned
if ($vertex === $superSource || $vertex === $superSink) {
continue;
}
$group = $vertex->getGroup();
// source
if ($group === $groupA) {
$superSource->createEdgeTo($vertex)->setCapacity(1)->setFlow(0);
// temporarily create edges from A->B for flow graph
$originalVertex = $this->graph->getVertex($vertex->getId());
foreach ($originalVertex->getVerticesEdgeTo() as $vertexTarget) {
$vertex->createEdgeTo($graphFlow->getVertex($vertexTarget->getId()))->setCapacity(1)->setFlow(0);
}
// sink
} elseif ($group === $groupB) {
$vertex->createEdgeTo($superSink)->setCapacity(1)->setFlow(0);
} else {
// @codeCoverageIgnoreStart
throw new LogicException('Should not happen. Unknown set: ' + $belongingSet);
// @codeCoverageIgnoreEnd
}
}
// visualize($resultGraph);
// calculate (s*, t*)-flow
$algMaxFlow = new MaxFlowEdmondsKarp($superSource, $superSink);
$resultGraph = $algMaxFlow->createGraph();
// destroy temporary supersource and supersink again
$resultGraph->getVertex($superSink->getId())->destroy();
$resultGraph->getVertex($superSource->getId())->destroy();
$returnEdges = array();
foreach ($resultGraph->getEdges() as $edge) {
// only keep matched edges
if ($edge->getFlow() > 0) {
$originalEdge = $this->graph->getEdgeClone($edge);
$returnEdges[] = $originalEdge;
}
}
return new Edges($returnEdges);
}
public function testGraphTriangleCycleIsNotBipartit()
{
// 1 -> 2 -> 3 -> 1
$graph = new Graph();
$v1 = $graph->createVertex(1)->setGroup(1);
$v2 = $graph->createVertex(2)->setGroup(2);
$v3 = $graph->createVertex(3)->setGroup(1);
$v1->createEdgeTo($v2);
$v2->createEdgeTo($v3);
$v3->createEdgeTo($v1);
$alg = new AlgorithmGroups($graph);
$this->assertEquals(array(1, 2), $alg->getGroups());
$this->assertEquals(2, $alg->getNumberOfGroups());
$this->assertTrue($alg->getVerticesGroup(123)->isEmpty());
$this->assertEquals(array(1 => $v1, 3 => $v3), $alg->getVerticesGroup(1)->getMap());
$this->assertFalse($alg->isBipartit());
}
/**
* checks whether the input graph's vertex groups are a valid bipartition
*
* @return boolean
* @uses AlgorithmGroups::isBipartit()
*/
public function isBipartitGroups()
{
$alg = new Groups($this->graph);
return $alg->isBipartit();
}
