Start of factor graph port. Things don't work yet, but a lot of syntax updates towards PHP

2025-04-01 05:34:00 +00:00 · 2010-09-18 11:11:44 -04:00
parent 4a76cc34cc
commit e434696b44
25 changed files with 1637 additions and 20 deletions
--- a/PHPSkills/TrueSkill/Factors/GaussianGreaterThanFactor.php
+++ b/PHPSkills/TrueSkill/Factors/GaussianGreaterThanFactor.php
@ -0,0 +1,73 @@
+<?php
+namespace Moserware\Skills\TrueSkill\Factors;
+
+/// <summary>
+/// Factor representing a team difference that has exceeded the draw margin.
+/// </summary>
+/// <remarks>See the accompanying math paper for more details.</remarks>
+class GaussianGreaterThanFactor extends GaussianFactor
+{
+    private $_epsilon;
+
+    public function __construct($epsilon, Variable $variable)
+    {
+        parent::_construct("{0} > {1:0.000}");
+        $this->_epsilon = $epsilon;
+        $this->createVariableToMessageBinding($variable);
+    }
+
+    public function getLogNormalization()
+    {
+        $vars = $this->getVariables();
+        $marginal = $vars[0]->getValue();
+        $messages = $this->getMessages();
+        $message = $messages[0]->getValue();
+        $messageFromVariable = GaussianDistribution::divide($marginal, $message);
+        return -GaussianDistribution::logProductNormalization($messageFromVariable, $message)
+               +
+               log(
+                   GaussianDistribution::cumulativeTo(($messageFromVariable->getMean() - $this->_epsilon)/
+                                                     $messageFromVariable->getStandardDeviation()));
+
+    }
+
+    protected function updateMessageVariable(Message $message, Variable $variable)
+    {
+        $oldMarginal = clone $variable->getValue();
+        $oldMessage = clone $message->getValue();
+        $messageFromVar = GaussianDistribution::divide($oldMarginal, $oldMessage);
+
+        $c = $messageFromVar->getPrecision();
+        $d = $messageFromVar->getPrecisionMean();
+
+        $sqrtC = sqrt($c);
+
+        $dOnSqrtC = $d/$sqrtC;
+
+        $epsilsonTimesSqrtC = $this->_epsilon*$sqrtC;
+        $d = $messageFromVar->getPrecisionMean();
+
+        $denom = 1.0 - TruncatedGaussianCorrectionFunctions::vExceedsMargin($dOnSqrtC, $epsilsonTimesSqrtC);
+
+        $newPrecision = $c/$denom;
+        $newPrecisionMean = ($d +
+                             $sqrtC*
+                             TruncatedGaussianCorrectionFunctions::vExceedsMargin($dOnSqrtC, $epsilsonTimesSqrtC))/
+                             $denom;
+
+        $newMarginal = GaussianDistribution::fromPrecisionMean($newPrecisionMean, $newPrecision);
+
+        $newMessage = GaussianDistribution::divide(
+                              GaussianDistribution::multiply($oldMessage, $newMarginal),
+                              $oldMarginal);
+
+        /// Update the message and marginal
+        $message->setValue($newMessage);
+
+        $variable->setValue($newMarginal);
+
+        /// Return the difference in the new marginal
+        return GaussianDistribution::subtract($newMarginal, $oldMarginal);
+    }
+}
+?>