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 *  * This program and the accompanying materials are made available under the
 *  * terms of the Apache License, Version 2.0 which is available at
 *  * https://www.apache.org/licenses/LICENSE-2.0.
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 *  *  See the NOTICE file distributed with this work for additional
 *  *  information regarding copyright ownership.
 *  * Unless required by applicable law or agreed to in writing, software
 *  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 *  * License for the specific language governing permissions and limitations
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package org.deeplearning4j.nn.conf.layers;

import lombok.Data;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import org.deeplearning4j.nn.api.ParamInitializer;
import org.deeplearning4j.nn.api.TrainingConfig;
import org.deeplearning4j.nn.api.layers.LayerConstraint;
import org.deeplearning4j.nn.conf.InputPreProcessor;
import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
import org.deeplearning4j.nn.conf.dropout.Dropout;
import org.deeplearning4j.nn.conf.dropout.IDropout;
import org.deeplearning4j.nn.conf.inputs.InputType;
import org.deeplearning4j.nn.conf.memory.LayerMemoryReport;
import org.deeplearning4j.optimize.api.TrainingListener;
import org.nd4j.linalg.api.buffer.DataType;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.learning.config.IUpdater;
import org.nd4j.linalg.learning.regularization.Regularization;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

import java.io.Serializable;
import java.lang.reflect.Field;
import java.util.*;

/**
 * A neural network layer.
 */

@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@class")
@Data
@NoArgsConstructor
public abstract class Layer implements TrainingConfig, Serializable, Cloneable {

    protected String layerName;
    protected IDropout iDropout;
    protected List<LayerConstraint> constraints;


    public Layer(Builder builder) {
        this.layerName = builder.layerName;
        this.iDropout = builder.iDropout;
    }

    /**
     * Initialize the weight constraints. Should be called last, in the outer-most constructor
     */
    protected void initializeConstraints(Builder<?> builder) {
        //Note: this has to be done AFTER all constructors have finished - otherwise the required
        // fields may not yet be set yet
        List<LayerConstraint> allConstraints = new ArrayList<>();
        if (builder.allParamConstraints != null && !initializer().paramKeys(this).isEmpty()) {
            for (LayerConstraint c : builder.allParamConstraints) {
                LayerConstraint c2 = c.clone();
                c2.setParams(new HashSet<>(initializer().paramKeys(this)));
                allConstraints.add(c2);
            }
        }

        if (builder.weightConstraints != null && !initializer().weightKeys(this).isEmpty()) {
            for (LayerConstraint c : builder.weightConstraints) {
                LayerConstraint c2 = c.clone();
                c2.setParams(new HashSet<>(initializer().weightKeys(this)));
                allConstraints.add(c2);
            }
        }

        if (builder.biasConstraints != null && !initializer().biasKeys(this).isEmpty()) {
            for (LayerConstraint c : builder.biasConstraints) {
                LayerConstraint c2 = c.clone();
                c2.setParams(new HashSet<>(initializer().biasKeys(this)));
                allConstraints.add(c2);
            }
        }
        if (!allConstraints.isEmpty()) {
            this.constraints = allConstraints;
        } else {
            this.constraints = null;
        }
        this.iDropout = builder.iDropout;
    }

    /**
     * Reset the learning related configs of the layer to default. When instantiated with a global
     * neural network configuration the parameters specified in the neural network configuration
     * will be used. For internal use with the transfer learning API. Users should not have to call
     * this method directly.
     */
    public void resetLayerDefaultConfig() {
        //clear the learning related params for all layers in the origConf and set to defaults
        this.iDropout = null;
        this.constraints = null;
    }

    @Override
    public Layer clone() {
        try {
            Layer ret = (Layer) super.clone();
            //Let's check for any INDArray fields and dup them (in case cloned layer will be used in different threads on CUDA...
            // we don't want it being relocated contantly between devices)
            Class<?> c = getClass();
            while (c != Object.class) {
                Field[] fields = c.getDeclaredFields();
                for (Field f : fields) {
                    if (f.getType() == INDArray.class) {
                        f.setAccessible(true);
                        INDArray toClone;
                        try {
                            toClone = (INDArray) f.get(this);
                        } catch (Exception e) {
                            throw new RuntimeException(e);
                        }
                        if (toClone != null) {
                            try {
                                f.set(this, toClone.dup());
                            } catch (Exception e) {
                                throw new RuntimeException(e);
                            }
                        }
                    }
                }

                c = c.getSuperclass();
            }

            return ret;
        } catch (CloneNotSupportedException e) {
            throw new RuntimeException(e);
        }
    }

    public abstract org.deeplearning4j.nn.api.Layer instantiate(NeuralNetConfiguration conf,
                                                                Collection<TrainingListener> trainingListeners, int layerIndex, INDArray layerParamsView,
                                                                boolean initializeParams, DataType networkDataType);

    /**
     * @return The parameter initializer for this model
     */
    public abstract ParamInitializer initializer();

    /**
     * For a given type of input to this layer, what is the type of the output?
     *
     * @param layerIndex Index of the layer
     * @param inputType Type of input for the layer
     * @return Type of output from the layer
     * @throws IllegalStateException if input type is invalid for this layer
     */
    public abstract InputType getOutputType(int layerIndex, InputType inputType);

    /**
     * Set the nIn value (number of inputs, or input channels for CNNs) based on the given input
     * type
     *
     * @param inputType Input type for this layer
     * @param override If false: only set the nIn value if it's not already set. If true: set it
     * regardless of whether it's already set or not.
     * @throws IllegalStateException if input type is invalid for this layer
     */
    public abstract void setNIn(InputType inputType, boolean override);


    /**
     * For the given type of input to this layer, what preprocessor (if any) is required?<br>
     * Returns null if no preprocessor is required, otherwise returns an appropriate {@link
     * InputPreProcessor} for this layer, such as a {@link org.deeplearning4j.nn.conf.preprocessor.CnnToFeedForwardPreProcessor}
     *
     * @param inputType InputType to this layer
     * @return Null if no preprocessor is required, otherwise the type of preprocessor necessary for
     * this layer/input combination
     * @throws IllegalStateException if input type is invalid for this layer
     */
    public abstract InputPreProcessor getPreProcessorForInputType(InputType inputType);

    /**
     * Get the regularization types (l1/l2/weight decay) for the given parameter. Different parameters may have different
     * regularization types.
     *
     * @param paramName Parameter name ("W", "b" etc)
     * @return Regularization types (if any) for the specified parameter
     */
    public abstract List<Regularization> getRegularizationByParam(String paramName);

    /**
     * Is the specified parameter a layerwise pretraining only parameter?<br> For example, visible
     * bias params in an autoencoder (or, decoder params in a variational autoencoder) aren't used
     * during supervised backprop.<br> Layers (like DenseLayer, etc) with no pretrainable parameters
     * will return false for all (valid) inputs.
     *
     * @param paramName Parameter name/key
     * @return True if the parameter is for layerwise pretraining only, false otherwise
     */
    public abstract boolean isPretrainParam(String paramName);

    /**
     * Get the updater for the given parameter. Typically the same updater will be used for all
     * updaters, but this is not necessarily the case
     *
     * @param paramName Parameter name
     * @return IUpdater for the parameter
     */
    public IUpdater getUpdaterByParam(String paramName) {
        throw new UnsupportedOperationException(
                        "Not supported: all layers with parameters should override this method");
    }

    @Override
    public void setDataType(DataType dataType) {
        //No-op for most layers
    }

    /**
     * This is a report of the estimated memory consumption for the given layer
     *
     * @param inputType Input type to the layer. Memory consumption is often a function of the input
     * type
     * @return Memory report for the layer
     */
    public abstract LayerMemoryReport getMemoryReport(InputType inputType);

    @SuppressWarnings("unchecked")
    @Getter
    @Setter
    public abstract static class Builder<T extends Builder<T>> {

        protected String layerName = null;

        protected List<LayerConstraint> allParamConstraints;

        protected List<LayerConstraint> weightConstraints;

        protected List<LayerConstraint> biasConstraints;

        protected IDropout iDropout;

        /**
         * Layer name assigns layer string name. Allows easier differentiation between layers.
         */
        public T name(String layerName) {
            this.setLayerName(layerName);
            return (T) this;
        }

        /**
         * Dropout probability. This is the probability of <it>retaining</it> each input activation
         * value for a layer. dropOut(x) will keep an input activation with probability x, and set
         * to 0 with probability 1-x.<br> dropOut(0.0) is a special value / special case - when set
         * to 0.0., dropout is disabled (not applied). Note that a dropout value of 1.0 is
         * functionally equivalent to no dropout: i.e., 100% probability of retaining each input
         * activation.<br> When useDropConnect(boolean) is set to true (false by default), this
         * method sets the drop connect probability instead.
         * <p>
         * Note 1: Dropout is applied at training time only - and is automatically not applied at
         * test time (for evaluation, etc)<br> Note 2: This sets the probability per-layer. Care
         * should be taken when setting lower values for complex networks (too much information may
         * be lost with aggressive (very low) dropout values).<br> Note 3: Frequently, dropout is
         * not applied to (or, has higher retain probability for) input (first layer) layers.
         * Dropout is also often not applied to output layers. This needs to be handled MANUALLY by
         * the user - set .dropout(0) on those layers when using global dropout setting.<br> Note 4:
         * Implementation detail (most users can ignore): DL4J uses inverted dropout, as described
         * here:
         * <a href="http://cs231n.github.io/neural-networks-2/">http://cs231n.github.io/neural-networks-2/</a>
         * </p>
         *
         * @param inputRetainProbability Dropout probability (probability of retaining each input
         * activation value for a layer)
         * @see #dropOut(IDropout)
         */
        public T dropOut(double inputRetainProbability) {
            if (inputRetainProbability == 0.0) {
                return dropOut(null);
            }
            return dropOut(new Dropout(inputRetainProbability));
        }

        /**
         * Set the dropout for all layers in this network
         *
         * @param dropout Dropout, such as {@link Dropout}, {@link org.deeplearning4j.nn.conf.dropout.GaussianDropout},
         * {@link org.deeplearning4j.nn.conf.dropout.GaussianNoise} etc
         */
        public T dropOut(IDropout dropout) {
            this.setIDropout(dropout);
            return (T) this;
        }

        /**
         * Set constraints to be applied to this layer. Default: no constraints.<br> Constraints can
         * be used to enforce certain conditions (non-negativity of parameters, max-norm
         * regularization, etc). These constraints are applied at each iteration, after the
         * parameters have been updated.
         *
         * @param constraints Constraints to apply to all parameters of this layer
         */
        public T constrainAllParameters(LayerConstraint... constraints) {
            this.setAllParamConstraints(Arrays.asList(constraints));
            return (T) this;
        }

        /**
         * Set constraints to be applied to bias parameters of this layer. Default: no
         * constraints.<br> Constraints can be used to enforce certain conditions (non-negativity of
         * parameters, max-norm regularization, etc). These constraints are applied at each
         * iteration, after the parameters have been updated.
         *
         * @param constraints Constraints to apply to all bias parameters of this layer
         */
        public T constrainBias(LayerConstraint... constraints) {
            this.setBiasConstraints(Arrays.asList(constraints));
            return (T) this;
        }

        /**
         * Set constraints to be applied to the weight parameters of this layer. Default: no
         * constraints.<br> Constraints can be used to enforce certain conditions (non-negativity of
         * parameters, max-norm regularization, etc). These constraints are applied at each
         * iteration, after the parameters have been updated.
         *
         * @param constraints Constraints to apply to all weight parameters of this layer
         */
        public T constrainWeights(LayerConstraint... constraints) {
            this.setWeightConstraints(Arrays.asList(constraints));
            return (T) this;
        }

        public abstract <E extends Layer> E build();
    }
}
