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49 lines
1.8 KiB
PHP
49 lines
1.8 KiB
PHP
<?php
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namespace Moserware\Skills\TrueSkill\Factors;
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require_once(dirname(__FILE__) . "/../../FactorGraphs/Message.php");
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require_once(dirname(__FILE__) . "/../../FactorGraphs/Variable.php");
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require_once(dirname(__FILE__) . "/../../Numerics/GaussianDistribution.php");
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require_once(dirname(__FILE__) . "/GaussianFactor.php");
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use Moserware\Numerics\GaussianDistribution;
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use Moserware\Skills\FactorGraphs\Message;
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use Moserware\Skills\FactorGraphs\Variable;
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/**
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* Supplies the factor graph with prior information.
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*
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* See the accompanying math paper for more details.
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*/
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class GaussianPriorFactor extends GaussianFactor
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{
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private $_newMessage;
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public function __construct($mean, $variance, Variable &$variable)
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{
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parent::__construct(sprintf("Prior value going to %s", $variable));
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$this->_newMessage = new GaussianDistribution($mean, sqrt($variance));
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$newMessage = new Message(GaussianDistribution::fromPrecisionMean(0, 0),
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sprintf("message from %s to %s", $this, $variable));
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$this->createVariableToMessageBindingWithMessage($variable, $newMessage);
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}
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protected function updateMessageVariable(Message &$message, Variable &$variable)
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{
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$oldMarginal = clone $variable->getValue();
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$oldMessage = $message;
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$newMarginal =
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GaussianDistribution::fromPrecisionMean(
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$oldMarginal->getPrecisionMean() + $this->_newMessage->getPrecisionMean() - $oldMessage->getValue()->getPrecisionMean(),
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$oldMarginal->getPrecision() + $this->_newMessage->getPrecision() - $oldMessage->getValue()->getPrecision());
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$variable->setValue($newMarginal);
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$newMessage = &$this->_newMessage;
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$message->setValue($newMessage);
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return GaussianDistribution::subtract($oldMarginal, $newMarginal);
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}
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}
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?>
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