/**
* Main visit function
*
* Visit function to process an automaton (directed, cyclic, discontinuous
* graph). No more detailed methods are defined, since the process of
* visiting is highly dependent on the concrete visitor implementation.
*
* Optionally labels may be passed for each node in the graph, which might
* be used during the rendering process.
*
* Returns an array with the support for each node, which just represents
* the number of incoming edges.
*
* @param slAutomaton $automaton
* @return array
*/
public function visit(slAutomaton $automaton, array $labels = array())
{
$nodes = $automaton->getNodes();
$ranks = array();
foreach ($nodes as $node) {
$ranks[$node] = count($automaton->getIncoming($node));
}
return $ranks;
}
/**
* Merge singleton nodes
*
* All equivalency classes which consist of just one nodes are considered
* singleton nodes. This method merges all maximum sets of singleton nodes,
* which share the same successors and precedessors.
*
* @param slAutomaton $automaton
* @return void
*/
protected function mergeSingletonNodes(slAutomaton $automaton)
{
$classes = array_keys($this->equivalenceClasses);
$classCount = count($classes);
for ($i = 0; $i < $classCount; ++$i) {
if (!isset($this->equivalenceClasses[$classes[$i]]) || count($this->equivalenceClasses[$classes[$i]]) > 1) {
// We only care for singletons
continue;
}
for ($j = $i + 1; $j < $classCount; ++$j) {
if (!isset($this->equivalenceClasses[$classes[$j]]) || count($this->equivalenceClasses[$classes[$j]]) > 1) {
// We only care for singletons
continue;
}
if ($automaton->getOutgoing($classes[$i]) === $automaton->getOutgoing($classes[$j]) && $automaton->getIncoming($classes[$i]) === $automaton->getIncoming($classes[$j])) {
$this->equivalenceClasses[$classes[$i]][] = $classes[$j];
unset($this->equivalenceClasses[$classes[$j]]);
$automaton->removeNode($classes[$j]);
}
}
}
}
/**
* Main visit function
*
* Visit function to process an automaton (directed, cyclic, discontinuous
* graph). No more detailed methods are defined, since the process of
* visiting is highly dependent on the concrete visitor implementation.
*
* Optionally labels may be passed for each node in the graph, which might
* be used during the rendering process.
*
* Returns an array with values for each node, representing their "imporance"
* in the graph based on Googles PageRank algorithm.
*
* @param slAutomaton $automaton
* @return array
*/
public function visit(slAutomaton $automaton, array $labels = array())
{
$nodes = $automaton->getNodes();
$ranks = array();
foreach ($nodes as $node) {
$ranks[$node] = 1;
}
for ($i = 0; $i < $this->iterations; ++$i) {
foreach ($nodes as $node) {
$rank = 0;
foreach ($automaton->getIncoming($node) as $src) {
$pr = $ranks[$src];
$c = count($automaton->getOutgoing($src));
$rank += $pr / $c;
}
$ranks[$node] = 1 - $this->dampingFactor + $this->dampingFactor * $rank;
}
}
return $ranks;
}
