From 72afeb7040104bd9825d0555637fb735eb8c9e5e Mon Sep 17 00:00:00 2001
From: Arkadiusz Kondas <arkadiusz.kondas@gmail.com>
Date: Tue, 9 Aug 2016 13:27:43 +0200
Subject: [PATCH] implements and test multilayer perceptron methods

---
 .../Exception/InvalidArgumentException.php    |  8 ++
 .../Network/MultilayerPerceptron.php          | 83 +++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/src/Phpml/Exception/InvalidArgumentException.php b/src/Phpml/Exception/InvalidArgumentException.php
index d280296..86cfd86 100644
--- a/src/Phpml/Exception/InvalidArgumentException.php
+++ b/src/Phpml/Exception/InvalidArgumentException.php
@@ -81,4 +81,12 @@ class InvalidArgumentException extends \Exception
     {
         return new self('Layer node class must implement Node interface');
     }
+
+    /**
+     * @return InvalidArgumentException
+     */
+    public static function invalidLayersNumber()
+    {
+        return new self('Provide at least 2 layers: 1 input and 1 output');
+    }
 }
diff --git a/src/Phpml/NeuralNetwork/Network/MultilayerPerceptron.php b/src/Phpml/NeuralNetwork/Network/MultilayerPerceptron.php
index c0f7df3..4079822 100644
--- a/src/Phpml/NeuralNetwork/Network/MultilayerPerceptron.php
+++ b/src/Phpml/NeuralNetwork/Network/MultilayerPerceptron.php
@@ -4,6 +4,89 @@ declare (strict_types = 1);
 
 namespace Phpml\NeuralNetwork\Network;
 
+use Phpml\Exception\InvalidArgumentException;
+use Phpml\NeuralNetwork\Layer;
+use Phpml\NeuralNetwork\Node\Bias;
+use Phpml\NeuralNetwork\Node\Input;
+use Phpml\NeuralNetwork\Node\Neuron;
+use Phpml\NeuralNetwork\Node\Neuron\Synapse;
+
 class MultilayerPerceptron extends LayeredNetwork
 {
+    /**
+     * @param array $layers
+     *
+     * @throws InvalidArgumentException
+     */
+    public function __construct(array $layers)
+    {
+        if (count($layers) < 2) {
+            throw InvalidArgumentException::invalidLayersNumber();
+        }
+
+        $this->addInputLayer(array_shift($layers));
+        $this->addNeuronLayers($layers);
+        $this->addBiasNodes();
+        $this->generateSynapses();
+    }
+
+    /**
+     * @param int $nodes
+     */
+    private function addInputLayer(int $nodes)
+    {
+        $this->addLayer(new Layer($nodes, Input::class));
+    }
+
+    /**
+     * @param array $layers
+     */
+    private function addNeuronLayers(array $layers)
+    {
+        foreach ($layers as $neurons) {
+            $this->addLayer(new Layer($neurons, Neuron::class));
+        }
+    }
+
+    private function generateSynapses()
+    {
+        $layersNumber = count($this->layers) - 1;
+        for ($i = 0; $i < $layersNumber; ++$i) {
+            $currentLayer = $this->layers[$i];
+            $nextLayer = $this->layers[$i + 1];
+            $this->generateLayerSynapses($nextLayer, $currentLayer);
+        }
+    }
+
+    private function addBiasNodes()
+    {
+        $biasLayers = count($this->layers) - 1;
+        for ($i = 0;$i < $biasLayers;++$i) {
+            $this->layers[$i]->addNode(new Bias());
+        }
+    }
+
+    /**
+     * @param Layer $nextLayer
+     * @param Layer $currentLayer
+     */
+    private function generateLayerSynapses(Layer $nextLayer, Layer $currentLayer)
+    {
+        foreach ($nextLayer->getNodes() as $nextNeuron) {
+            if ($nextNeuron instanceof Neuron) {
+                $this->generateNeuronSynapses($currentLayer, $nextNeuron);
+            }
+        }
+    }
+
+    /**
+     * @param Layer  $currentLayer
+     * @param Neuron $nextNeuron
+     */
+    private function generateNeuronSynapses(Layer $currentLayer, Neuron $nextNeuron)
+    {
+        foreach ($currentLayer->getNodes() as $currentNeuron) {
+            $nextNeuron->addSynapse(new Synapse($currentNeuron));
+        }
+    }
 }