/**
* setpropagatelearn
*
* add free decision (a positive literal) to decision queue
* increase level and propagate decision
* return if no conflict.
*
* in conflict case, analyze conflict rule, add resulting
* rule to learnt rule set, make decision from learnt
* rule (always unit) and re-propagate.
*
* returns the new solver level or 0 if unsolvable
*
* @param int $level
* @param string|int $literal
* @param bool $disableRules
* @param Rule $rule
* @return int
*/
private function setPropagateLearn($level, $literal, $disableRules, Rule $rule)
{
$level++;
$this->decisions->decide($literal, $level, $rule);
while (true) {
$rule = $this->propagate($level);
if (!$rule) {
break;
}
if ($level == 1) {
return $this->analyzeUnsolvable($rule, $disableRules);
}
// conflict
list($learnLiteral, $newLevel, $newRule, $why) = $this->analyze($level, $rule);
if ($newLevel <= 0 || $newLevel >= $level) {
throw new SolverBugException("Trying to revert to invalid level " . (int) $newLevel . " from level " . (int) $level . ".");
} elseif (!$newRule) {
throw new SolverBugException("No rule was learned from analyzing {$rule} at level {$level}.");
}
$level = $newLevel;
$this->revert($level);
$this->rules->add($newRule, RuleSet::TYPE_LEARNED);
$this->learnedWhy[spl_object_hash($newRule)] = $why;
$ruleNode = new RuleWatchNode($newRule);
$ruleNode->watch2OnHighest($this->decisions);
$this->watchGraph->insert($ruleNode);
$this->decisions->decide($learnLiteral, $level, $newRule);
}
return $level;
}
