org.encog.mathutil.matrices.hessian

## Interface ComputeHessian

- All Known Implementing Classes:
    BasicHessian, HessianCR, HessianFD

      public interface ComputeHessian

  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

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()` Clear the Hessian and gradients.
    `void` | `compute()` Compute the Hessian.
    `double[]` | `getGradients()` The gradeints.
    `double[][]` | `getHessian()`
    `Matrix` | `getHessianMatrix()`
    `double` | `getSSE()`
    `void` | `init(BasicNetwork theNetwork, MLDataSet theTraining)` Init the class.

- - ### Method Detail

    - #### init

          void init(BasicNetwork theNetwork,
                  MLDataSet theTraining)

      Init the class.
      Parameters:
        `theNetwork` - The neural network to train.
        `theTraining` - The training set to train with.

    - #### compute

          void compute()

      Compute the Hessian.

    - #### getGradients

          double[] getGradients()

      The gradeints.
      Returns:
        The gradients for the Hessian.

    - #### getSSE

          double getSSE()

      Returns:
        The sum of squares error over all of the training elements.

    - #### clear

          void clear()

      Clear the Hessian and gradients.

    - #### getHessianMatrix

          Matrix getHessianMatrix()

      Returns:
        The Hessian matrix.

    - #### getHessian

          double[][] getHessian()

      Returns:
        Get the Hessian as a 2d array.

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