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gnn_criterion.h

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/***************************************************************************
 *  @file gnn_criterion.h
 *  @brief Basic Structure for Criterions.
 *
 *  @date   : 24-08-03 19:28
 *  @author : Pedro Ortega C. <peortega@dcc.uchile.cl>
 *  Copyright  2003  Pedro Ortega C.
 ****************************************************************************/
/*
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Library General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#ifndef _GNN_CRITERION_H_
#define _GNN_CRITERION_H_

/******************************************/
/* Include Files                          */
/******************************************/

#include "gnn_globals.h"



/******************************************/
/* Typedefs                               */
/******************************************/

/**
 * @brief The datatype for criterions.
 * @ingroup gnn_criterion_doc
 *
 * This is the datatype on which all implementations of criterions build on.
 * It basically contains buffers for intermediate values and three pointers
 * for the criterion's methods.
 */
typedef struct _gnn_criterion gnn_criterion;

/**
 * @brief The datatype for criterions evaluation functions.
 * @ingroup gnn_criterion_doc
 *
 * This datatype defines the form for \ref gnn_criterion's evaluation functions.
 * It takes a pointer to the current criterion, the vectors \f$y\f$ (model
 * output/estimation) and \f$t\f$ (desired target value). The function should
 * return a real value (double) that provides an adecuate optimization
 * criterion. Remember that \ref gnn_trainer's minimize the criterions.
 */
typedef double (*gnn_criterion_e) (gnn_criterion *crit,
                                   const gsl_vector *y,
                                   const gsl_vector *t);

/**
 * @brief The datatype for \f$\frac{\partial E}{\partial y}\f$.
 * @ingroup gnn_criterion_doc
 *
 * This datatype defines the form for \ref gnn_criterion's
 * \f$\frac{\partial E}{\partial y}\f$ gradient evaluation functions.
 * It takes a pointer to the current criterion, the vectors \f$y\f$ (model
 * output/estimation) and \f$t\f$ (desired target value). The function should
 * ADD the resulting gradient onto the values stored in the buffer pointed
 * by "dy".
 */
typedef int (*gnn_criterion_dy) (gnn_criterion *crit,
                                 const gsl_vector *y,
                                 const gsl_vector *t,
                                 gsl_vector * dy);

/**
 * @brief The datatype for destructors for criterion extensions.
 * @ingroup gnn_criterion_doc
 *
 * This datatype defines the form for \ref gnn_criterion's destructors.
 * If your specific implementation of a \ref gnn_criterion has additional
 * resources, then they (and nothing else) should be freed by this function,
 * and then return.
 */
typedef void (*gnn_criterion_destructor) (gnn_criterion *crit);

struct _gnn_criterion
{
    const char      *type;    /**< The criterion's type.                     */
    size_t           m;       /**< The size \f$m\f$ of the estimaton and the
                                   target vectors \f$y\f$ and \f$t\f$.       */

    const gsl_vector *y;      /**< Pointer to the last evaluated output.     */
    const gsl_vector *t;      /**< Pointer to the last evaluated target.     */

    gnn_criterion_e  e;               /**< Pointer to the criterion
                                           evaluation function.              */
    gnn_criterion_dy dy;              /**< Pointer to the gradient
                                           evaluation function.              */
    gnn_criterion_destructor destroy; /**< Pointer to the criterion
                                           destructor function.              */
};



/******************************************/
/* Public Interface                       */
/******************************************/

int
gnn_criterion_init (gnn_criterion *crit,
                    const char    *type,
                    size_t         size,
                    gnn_criterion_e          e,
                    gnn_criterion_dy         dy,
                    gnn_criterion_destructor destroy);

size_t
gnn_criterion_get_size (gnn_criterion *crit);

const char *
gnn_criterion_get_type (gnn_criterion *crit);

double
gnn_criterion_evaluate_e (gnn_criterion *crit,
                          const gsl_vector *y,
                          const gsl_vector *t);

int
gnn_criterion_evaluate_dy (gnn_criterion *crit,
                           gsl_vector *dy);

void
gnn_criterion_destroy (gnn_criterion *crit);

int
gnn_criterion_eval_dy (gnn_criterion *crit,
                       gsl_vector *dy);



#endif /* _GNN_CRITERION_H_ */

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