/**
* This is the standard DeltaBlue benchmark. A long chain of equality
* constraints is constructed with a stay constraint on one end. An
* edit constraint is then added to the opposite end and the time is
* measured for adding and removing this constraint, and extracting
* and executing a constraint satisfaction plan. There are two cases.
* In case 1, the added constraint is stronger than the stay
* constraint and values must propagate down the entire length of the
* chain. In case 2, the added constraint is weaker than the stay
* constraint so it cannot be accomodated. The cost in this case is,
* of course, very low. Typical situations lie somewhere between these
* two extremes.
*/
function chainTest($n)
{
global $planner;
$planner = new Planner();
$prev = null;
$first = null;
$last = null;
// Build chain of n equality constraints
for ($i = 0; $i <= $n; $i++) {
$name = "v{$i}";
$v = new Variable($name);
if ($prev != null) {
new EqualityConstraint($prev, $v, Strength::Required());
}
if ($i == 0) {
$first = $v;
}
if ($i == $n) {
$last = $v;
}
$prev = $v;
}
new StayConstraint($last, Strength::StrongDefault());
$edit = new EditConstraint($first, Strength::Preferred());
$edits = new OrderedCollection();
$edits->add($edit);
$plan = $planner->extractPlanFromConstraints($edits);
for ($i = 0; $i < 100; $i++) {
$first->value = $i;
$plan->execute();
if ($last->value != $i) {
alert("Chain test failed.");
}
}
}
