LaRank.h

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// -*- C++ -*-
// Main functions of the LaRank algorithm for soving Multiclass SVM
// Copyright (C) 2008- Antoine Bordes
// Shogun specific adjustments (w) 2009 Soeren Sonnenburg

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 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 General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
/***********************************************************************
 *
 *  LUSH Lisp Universal Shell
 *    Copyright (C) 2002 Leon Bottou, Yann Le Cun, AT&T Corp, NECI.
 *  Includes parts of TL3:
 *    Copyright (C) 1987-1999 Leon Bottou and Neuristique.
 *  Includes selected parts of SN3.2:
 *    Copyright (C) 1991-2001 AT&T Corp.
 *
 *  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 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, USA
 *
 ***********************************************************************/

/***********************************************************************
 * $Id: kcache.h,v 1.8 2007/01/25 22:42:09 leonb Exp $
 **********************************************************************/

#ifndef LARANK_H
#define LARANK_H

#include <vector>
#include <set>
#include <map>
#define STDEXT_NAMESPACE __gnu_cxx
#define std_hash_map std::map
#define std_hash_set std::set

#include <shogun/lib/config.h>

#include <shogun/io/SGIO.h>
#include <shogun/kernel/Kernel.h>
#include <shogun/multiclass/MulticlassSVM.h>

namespace shogun
{
#ifndef DOXYGEN_SHOULD_SKIP_THIS
    struct larank_kcache_s;
    typedef struct larank_kcache_s larank_kcache_t;
    struct larank_kcache_s
    {
        CKernel* func;
        larank_kcache_t *prevbuddy;
        larank_kcache_t *nextbuddy;
        int64_t maxsize;
        int64_t cursize;
        int32_t l;
        int32_t *i2r;
        int32_t *r2i;
        int32_t maxrowlen;
        /* Rows */
        int32_t *rsize;
        float32_t *rdiag;
        float32_t **rdata;
        int32_t *rnext;
        int32_t *rprev;
        int32_t *qnext;
        int32_t *qprev;
    };

    /*
     ** OUTPUT: one per class of the raining set, keep tracks of support
     * vectors and their beta coefficients
     */
    class LaRankOutput
    {
        public:
            LaRankOutput () : beta(NULL), g(NULL), kernel(NULL), l(0)
        {
        }
            virtual ~LaRankOutput ()
            {
                destroy();
            }

            // Initializing an output class (basically creating a kernel cache for it)
            void initialize (CKernel* kfunc, int64_t cache);

            // Destroying an output class (basically destroying the kernel cache)
            void destroy ();

            // !Important! Computing the score of a given input vector for the actual output
            float64_t computeScore (int32_t x_id);

            // !Important! Computing the gradient of a given input vector for the actual output
            float64_t computeGradient (int32_t xi_id, int32_t yi, int32_t ythis);

            // Updating the solution in the actual output
            void update (int32_t x_id, float64_t lambda, float64_t gp);

            // Linking the cache of this output to the cache of an other "buddy" output
            // so that if a requested value is not found in this cache, you can
            // ask your buddy if it has it.
            void set_kernel_buddy (larank_kcache_t * bud);

            // Removing useless support vectors (for which beta=0)
            int32_t cleanup ();

            // --- Below are information or "get" functions --- //

            //
            inline larank_kcache_t *getKernel () const
            {
                return kernel;
            }
            //
            inline int32_t get_l () const
            {
                return l;
            }

            //
            float64_t getW2 ();

            //
            float64_t getKii (int32_t x_id);

            //
            float64_t getBeta (int32_t x_id);

            //
            inline float32_t* getBetas () const
            {
                return beta;
            }

            //
            float64_t getGradient (int32_t x_id);

            //
            bool isSupportVector (int32_t x_id) const;

            //
            int32_t getSV (float32_t* &sv) const;

        private:
            // the solution of LaRank relative to the actual class is stored in
            // this parameters
            float32_t* beta;        // Beta coefficiens
            float32_t* g;       // Strored gradient derivatives
            larank_kcache_t *kernel;    // Cache for kernel values
            int32_t l;          // Number of support vectors
    };

    /*
     ** LARANKPATTERN: to keep track of the support patterns
     */
    class LaRankPattern
    {
        public:
            LaRankPattern (int32_t x_index, int32_t label)
                : x_id (x_index), y (label) {}
            LaRankPattern ()
                : x_id (0) {}

            bool exists () const
            {
                return x_id >= 0;
            }

            void clear ()
            {
                x_id = -1;
            }

            int32_t x_id;
            int32_t y;
    };

    /*
     **  LARANKPATTERNS: the collection of support patterns
     */
    class LaRankPatterns
    {
        public:
            LaRankPatterns () {}
            ~LaRankPatterns () {}

            void insert (const LaRankPattern & pattern)
            {
                if (!isPattern (pattern.x_id))
                {
                    if (freeidx.size ())
                    {
                        std_hash_set < uint32_t >::iterator it = freeidx.begin ();
                        patterns[*it] = pattern;
                        x_id2rank[pattern.x_id] = *it;
                        freeidx.erase (it);
                    }
                    else
                    {
                        patterns.push_back (pattern);
                        x_id2rank[pattern.x_id] = patterns.size () - 1;
                    }
                }
                else
                {
                    int32_t rank = getPatternRank (pattern.x_id);
                    patterns[rank] = pattern;
                }
            }

            void remove (uint32_t i)
            {
                x_id2rank[patterns[i].x_id] = 0;
                patterns[i].clear ();
                freeidx.insert (i);
            }

            bool empty () const
            {
                return patterns.size () == freeidx.size ();
            }

            uint32_t size () const
            {
                return patterns.size () - freeidx.size ();
            }

            LaRankPattern & sample ()
            {
                ASSERT (!empty ())
                while (true)
                {
                    uint32_t r = CMath::random(uint32_t(0), uint32_t(patterns.size ()-1));
                    if (patterns[r].exists ())
                        return patterns[r];
                }
                return patterns[0];
            }

            uint32_t getPatternRank (int32_t x_id)
            {
                return x_id2rank[x_id];
            }

            bool isPattern (int32_t x_id)
            {
                return x_id2rank[x_id] != 0;
            }

            LaRankPattern & getPattern (int32_t x_id)
            {
                uint32_t rank = x_id2rank[x_id];
                return patterns[rank];
            }

            uint32_t maxcount () const
            {
                return patterns.size ();
            }

            LaRankPattern & operator [] (uint32_t i)
            {
                return patterns[i];
            }

            const LaRankPattern & operator [] (uint32_t i) const
            {
                return patterns[i];
            }

        private:
            std_hash_set < uint32_t >freeidx;
            std::vector < LaRankPattern > patterns;
            std_hash_map < int32_t, uint32_t >x_id2rank;
    };


#endif // DOXYGEN_SHOULD_SKIP_THIS


    class CLaRank:  public CMulticlassSVM
    {
        public:
            CLaRank ();

            CLaRank(float64_t C, CKernel* k, CLabels* lab);

            virtual ~CLaRank ();

            // LEARNING FUNCTION: add new patterns and run optimization steps
            // selected with adaptative schedule
            virtual int32_t add (int32_t x_id, int32_t yi);

            // PREDICTION FUNCTION: main function in la_rank_classify
            virtual int32_t predict (int32_t x_id);

            virtual void destroy ();

            // Compute Duality gap (costly but used in stopping criteria in batch mode)
            virtual float64_t computeGap ();

            // Nuber of classes so far
            virtual uint32_t getNumOutputs () const;

            // Number of Support Vectors
            int32_t getNSV ();

            // Norm of the parameters vector
            float64_t computeW2 ();

            // Compute Dual objective value
            float64_t getDual ();

            virtual EMachineType get_classifier_type() { return CT_LARANK; }

            virtual const char* get_name() const { return "LaRank"; }

            void set_batch_mode(bool enable) { batch_mode=enable; };
            bool get_batch_mode() { return batch_mode; };
            void set_tau(float64_t t) { tau=t; };
            float64_t get_tau() { return tau; };

        protected:
            bool train_machine(CFeatures* data);

        private:
            /*
             ** MAIN DARK OPTIMIZATION PROCESSES
             */

            // Hash Table used to store the different outputs
            typedef std_hash_map < int32_t, LaRankOutput > outputhash_t;    // class index -> LaRankOutput

            outputhash_t outputs;

            LaRankOutput *getOutput (int32_t index);

            //
            LaRankPatterns patterns;

            // Parameters
            int32_t nb_seen_examples;
            int32_t nb_removed;

            // Numbers of each operation performed so far
            int32_t n_pro;
            int32_t n_rep;
            int32_t n_opt;

            // Running estimates for each operations
            float64_t w_pro;
            float64_t w_rep;
            float64_t w_opt;

            int32_t y0;
            float64_t m_dual;

            struct outputgradient_t
            {
                outputgradient_t (int32_t result_output, float64_t result_gradient)
                    : output (result_output), gradient (result_gradient) {}
                outputgradient_t ()
                    : output (0), gradient (0) {}

                int32_t output;
                float64_t gradient;

                bool operator < (const outputgradient_t & og) const
                {
                    return gradient > og.gradient;
                }
            };

            //3 types of operations in LaRank
            enum process_type
            {
                processNew,
                processOld,
                processOptimize
            };

            struct process_return_t
            {
                process_return_t (float64_t dual, int32_t yprediction)
                    : dual_increase (dual), ypred (yprediction) {}
                process_return_t () {}
                float64_t dual_increase;
                int32_t ypred;
            };

            // IMPORTANT Main SMO optimization step
            process_return_t process (const LaRankPattern & pattern, process_type ptype);

            // ProcessOld
            float64_t reprocess ();

            // Optimize
            float64_t optimize ();

            // remove patterns and return the number of patterns that were removed
            uint32_t cleanup ();

        protected:

            std_hash_set < int32_t >classes;

            inline uint32_t class_count () const
            {
                return classes.size ();
            }

            float64_t tau;

            int32_t nb_train;
            int64_t cache;
            bool batch_mode;

            int32_t step;
    };
}
#endif // LARANK_H