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41 lines
1.5 KiB
PHP
41 lines
1.5 KiB
PHP
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<?php
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namespace Moserware\Skills\TrueSkill\Factors;
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/// <summary>
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/// Supplies the factor graph with prior information.
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/// </summary>
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/// <remarks>See the accompanying math paper for more details.</remarks>
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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 $variable)
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{
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parent::__construct("Prior value going to {0}");
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$this->_newMessage = new GaussianDistribution($mean, sqrt($variance));
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$this->createVariableToMessageBinding($variable,
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new Message(
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GaussianDistribution::fromPrecisionMean(0, 0),
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"message from {0} to {1}",
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this, variable));
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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($newMarginal);
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$message->setValue($this->_newMessage);
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return GaussianDistribution::subtract($oldMarginal, $newMarginal);
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}
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}
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?>
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