Viewing file:  RuleWatchNode.php (2.86 KB) -rw-r--r--
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<?php declare(strict_types=1);
/*
* This file is part of Composer.
*
* (c) Nils Adermann <naderman@naderman.de>
* Jordi Boggiano <j.boggiano@seld.be>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Composer\DependencyResolver;
/**
* Wrapper around a Rule which keeps track of the two literals it watches
*
* Used by RuleWatchGraph to store rules in two RuleWatchChains.
*
* @author Nils Adermann <naderman@naderman.de>
*/
class RuleWatchNode
{
/** @var int */
public $watch1;
/** @var int */
public $watch2;
/** @var Rule */
protected $rule;
/**
* Creates a new node watching the first and second literals of the rule.
*
* @param Rule $rule The rule to wrap
*/
public function __construct(Rule $rule)
{
$this->rule = $rule;
$literals = $rule->getLiterals();
$literalCount = \count($literals);
$this->watch1 = $literalCount > 0 ? $literals[0] : 0;
$this->watch2 = $literalCount > 1 ? $literals[1] : 0;
}
/**
* Places the second watch on the rule's literal, decided at the highest level
*
* Useful for learned rules where the literal for the highest rule is most
* likely to quickly lead to further decisions.
*
* @param Decisions $decisions The decisions made so far by the solver
*/
public function watch2OnHighest(Decisions $decisions): void
{
$literals = $this->rule->getLiterals();
// if there are only 2 elements, both are being watched anyway
if (\count($literals) < 3 || $this->rule instanceof MultiConflictRule) {
return;
}
$watchLevel = 0;
foreach ($literals as $literal) {
$level = $decisions->decisionLevel($literal);
if ($level > $watchLevel) {
$this->watch2 = $literal;
$watchLevel = $level;
}
}
}
/**
* Returns the rule this node wraps
*/
public function getRule(): Rule
{
return $this->rule;
}
/**
* Given one watched literal, this method returns the other watched literal
*
* @param int $literal The watched literal that should not be returned
* @return int A literal
*/
public function getOtherWatch(int $literal): int
{
if ($this->watch1 === $literal) {
return $this->watch2;
}
return $this->watch1;
}
/**
* Moves a watch from one literal to another
*
* @param int $from The previously watched literal
* @param int $to The literal to be watched now
*/
public function moveWatch(int $from, int $to): void
{
if ($this->watch1 === $from) {
$this->watch1 = $to;
} else {
$this->watch2 = $to;
}
}
}
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