/*
* Encog(tm) Core v3.4 - Java Version
* http://www.heatonresearch.com/encog/
* https://github.com/encog/encog-java-core
* Copyright 2008-2016 Heaton Research, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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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* and trademarks visit:
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*/
package org.encog.mathutil.matrices.hessian;
import org.encog.mathutil.matrices.Matrix;
import org.encog.ml.data.MLDataSet;
import org.encog.neural.networks.BasicNetwork;
/**
* Compute (estimate) the Hessian matrix. The Hessian matrix is a matrix of the second
* derivatives of the neural network. This is a square matrix with rows and columns
* equal to the number of weights in the neural network.
*
* A Hessian matrix is useful for several neural network functions. It is also used
* by the Levenberg Marquardt training method.
*
* http://en.wikipedia.org/wiki/Hessian_matrix
*/
public interface ComputeHessian {
/**
* Init the class.
* @param theNetwork The neural network to train.
* @param theTraining The training set to train with.
*/
void init(BasicNetwork theNetwork, MLDataSet theTraining);
/**
* Compute the Hessian.
*/
void compute();
/**
* The gradeints.
* @return The gradients for the Hessian.
*/
double[] getGradients();
/**
* @return The sum of squares error over all of the training elements.
*/
double getSSE();
/**
* Clear the Hessian and gradients.
*/
void clear();
/**
* @return The Hessian matrix.
*/
public Matrix getHessianMatrix();
/**
* @return Get the Hessian as a 2d array.
*/
public double[][] getHessian();
}