/*
 *  ******************************************************************************
 *  *
 *  *
 *  * 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.
 *  *
 *  *  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
 *  * under the License.
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 *  * SPDX-License-Identifier: Apache-2.0
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 */

package org.nd4j.weightinit.impl;

import lombok.Builder;
import org.nd4j.linalg.api.buffer.DataType;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.factory.Nd4j;
import org.nd4j.weightinit.BaseWeightInitScheme;
import org.nd4j.weightinit.WeightInit;

public class XavierUniformInitScheme extends BaseWeightInitScheme {

    private double fanIn;
    private double fanOut;

    @Builder
    public XavierUniformInitScheme(char order, double fanIn, double fanOut) {
        super(order);
        this.fanIn = fanIn;
        this.fanOut = fanOut;
    }


    @Override
    public INDArray doCreate(DataType dataType, long[] shape, INDArray paramsView) {
        //As per Glorot and Bengio 2010: Uniform distribution U(-s,s) with s = sqrt(6/(fanIn + fanOut))
        //Eq 16: http://jmlr.org/proceedings/papers/v9/glorot10a/glorot10a.pdf
        double s = Math.sqrt(6.0) / Math.sqrt(fanIn + fanOut);
        return Nd4j.rand(Nd4j.getDistributions().createUniform(-s, s), shape);
    }


    @Override
    public WeightInit type() {
        return WeightInit.XAVIER_UNIFORM;
    }
}
