o3de-extras/Gems/MachineLearning/Code/Source/Models/MultilayerPerceptron.h

/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */

#pragma once

#include <AzCore/Math/MatrixMxN.h>
#include <MachineLearning/INeuralNetwork.h>
#include <Models/Layer.h>

namespace MachineLearning
{
    //! This is a basic multilayer perceptron neural network capable of basic training and feed forward operations.
    class MultilayerPerceptron
        : public INeuralNetwork
    {
    public:

        AZ_TYPE_INFO(MultilayerPerceptron, "{E12EF761-41A5-48C3-BF55-7179B280D45F}");

        //! AzCore Reflection.
        //! @param context reflection context
        static void Reflect(AZ::ReflectContext* context);

        MultilayerPerceptron() = default;
        MultilayerPerceptron(AZStd::size_t activationCount);
        virtual ~MultilayerPerceptron() = default;

        void AddLayer(AZStd::size_t layerDimensionality);
        AZStd::size_t GetLayerCount() const;
        Layer& GetLayer(AZStd::size_t layerIndex);

        AZStd::size_t GetParameterCount() const override;
        const AZ::VectorN& FeedForward(const AZ::VectorN& activations) override;
        float ComputeCost(const AZ::VectorN& activations, const AZ::VectorN& expectedOutput, CostFunctions costFunction) override;

    private:

        void OnActivationCountChanged();
        float ComputeCost_Quadratic(const AZ::VectorN& activations, const AZ::VectorN& expectedOutput);

        //! The number of neurons in the activation layer.
        AZStd::size_t m_activationCount = 0;

        //! The set of layers in the network.
        AZStd::vector<Layer> m_layers;
    };
}