/**
* Main program.
*
* @param array $args Command-line arguments.
* @return integer Zero on succes; non-zero on failure.
*/
public static function main($args)
{
printf("Demonstration program number 10.\n");
$status = 0;
GraphAsMatrix::main($args);
GraphAsLists::main($args);
DigraphAsMatrix::main($args);
DigraphAsLists::main($args);
return $status;
}
/**
* Computes the critical path in an event-node graph.
*
* @param object IDigraph $g An edge-weighted, directed acylic graph.
* It is assumed that the edge weights are <code>Int</code>s
* @return object IDigraph A vertex-weighted, directed graph.
* The events (vertices) on the critical path have zero weight.
* The one edge that emantes from a vertex connects that vertex
* to its predecessor on the critical path.
*/
public static function criticalPathAnalysis(IDigraph $g)
{
$n = $g->getNumberOfVertices();
$earliestTime = new BasicArray($n);
$earliestTime[0] = 0;
$g->topologicalOrderTraversal(new EarliestTimeVisitor($earliestTime));
$latestTime = new BasicArray($n);
$latestTime[$n - 1] = $earliestTime[$n - 1];
$g->depthFirstTraversal(new PostOrder(new LatestTimeVisitor($latestTime)), 0);
$slackGraph = new DigraphAsLists($n);
for ($v = 0; $v < $n; ++$v) {
$slackGraph->addVertex($v);
}
foreach ($g->getEdges() as $edge) {
$n0 = $edge->getV0()->getNumber();
$n1 = $edge->getV1()->getNumber();
$wt = $edge->getWeight();
$slack = $latestTime[$n1] - $earliestTime[$n0] - unbox($wt);
$slackGraph->addEdge($n0, $n1, box($slack));
}
return Algorithms::dijkstrasAlgorithm($slackGraph, 0);
}
