lstm.h

/*
 * Copyright (c) 2015 Vrije Universiteit Brussel
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef __LSTM_H__
#define __LSTM_H__

#include "abstractrecurrentnetworknode.h"

class MergeSum;
class MergeProduct;

/**
 * @brief Long Short-Term Memory layer
 *
 * This layer contains memory and can be used to model sequences of input. At
 * each time step, the value it produces depends on all the previous time steps.
 * An episode is finished by calling reset(), which Network::reset() does.
 */
class LSTM : public AbstractRecurrentNetworkNode
{
    public:
        /**
         * @brief Layer of LSTM cells. All the input and output ports of this
         *        layer have the same shape.
         *
         * @note This constructor wires some recurrent connexions (output to inGate,
         *       outGate and forgetGate). Adding more connexions is possible by
         *       calling addInput, addInGate, addOutGate and addForgetGate. For
         *       instance, the input is often connected to inGate, outGate and
         *       forgetGate. See GRU::GRU for advice about those connections.
         */
        LSTM(unsigned int size, Float learning_rate, Float decay = 0.9f);

        /**
         * @brief Add an X input to this network
         */
        void addInput(Port *input);

        /**
         * @brief Add an input gate input to this network
         */
        void addInGate(Port *in);

        /**
         * @brief Add an output gate input to this network
         */
        void addOutGate(Port *out);

        /**
         * @brief Add a forget gate input to this network
         */
        void addForgetGate(Port *forget);

        virtual Port* output();

    private:
        MergeSum *_inputs;
        MergeSum *_ingates;
        MergeSum *_outgates;
        MergeSum *_forgetgates;
        MergeSum *_cells;
        MergeProduct *_output;

};

#endif