PrimalMosekSOSVM.cpp

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/*
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2012 Fernando José Iglesias García
 * Copyright (C) 2012 Fernando José Iglesias García
 */

#ifdef USE_MOSEK

#include <shogun/lib/DynamicObjectArray.h>
#include <shogun/lib/List.h>
#include <shogun/mathematics/Math.h>
#include <shogun/structure/PrimalMosekSOSVM.h>

using namespace shogun;

CPrimalMosekSOSVM::CPrimalMosekSOSVM()
: CLinearStructuredOutputMachine()
{
}

CPrimalMosekSOSVM::CPrimalMosekSOSVM(
        CStructuredModel*  model,
        CLossFunction*     loss,
        CStructuredLabels* labs)
: CLinearStructuredOutputMachine(model, loss, labs)
{
}

void CPrimalMosekSOSVM::init()
{
    SG_ADD(&m_slacks, "m_slacks", "Slacks vector", MS_NOT_AVAILABLE);
}

CPrimalMosekSOSVM::~CPrimalMosekSOSVM()
{
}

bool CPrimalMosekSOSVM::train_machine(CFeatures* data)
{
    if (data)
        set_features(data);

    CFeatures* model_features = get_features();
    // Check that the scenary is correct to start with training
    m_model->check_training_setup();

    // Dimensionality of the joint feature space
    int32_t M = m_model->get_dim();
    // Number of auxiliary variables in the optimization vector
    int32_t num_aux = m_model->get_num_aux();
    // Number of auxiliary constraints
    int32_t num_aux_con = m_model->get_num_aux_con();
    // Number of training examples
    int32_t N = model_features->get_num_vectors();

    // Interface with MOSEK
    CMosek* mosek = new CMosek(0, M+num_aux+N);
    SG_REF(mosek);
    if ( mosek->get_rescode() != MSK_RES_OK )
    {
        SG_PRINT("Mosek object could not be properly created..."
             "aborting training of PrimalMosekSOSVM\n");

        return false;
    }

    // Initialize the terms of the optimization problem
    SGMatrix< float64_t > A, B, C;
    SGVector< float64_t > a, b, lb, ub;
    m_model->init_opt(A, a, B, b, lb, ub, C);

    // Input terms of the problem that do not change between iterations
    if ( mosek->init_sosvm(M, N, num_aux, num_aux_con, C, lb, ub, A, b) != MSK_RES_OK )
    {
        // MOSEK error took place
        return false;
    }

    // Initialize the weight vector
    m_w = SGVector< float64_t >(M);
    m_w.zero();

    m_slacks = SGVector< float64_t >(N);
    m_slacks.zero();

    // Initialize the list of constraints
    // Each element in results is a list of CResultSet with the constraints 
    // associated to each training example
    CDynamicObjectArray* results = new CDynamicObjectArray(N);
    SG_REF(results);
    for ( int32_t i = 0 ; i < N ; ++i )
    {
        CList* list = new CList(true);
        results->push_back(list);
    }

    // Initialize variables used in the loop
    int32_t     num_con     = num_aux_con;  // number of constraints
    int32_t     old_num_con = num_con;
    float64_t   slack       = 0.0;
    float64_t   max_slack   = 0.0;
    CResultSet* result      = NULL;
    CResultSet* cur_res     = NULL;
    CList*      cur_list    = NULL;
    bool        exception   = false;

    SGVector< float64_t > sol(M+num_aux+N);
    sol.zero();

    SGVector< float64_t > aux(num_aux);

    do 
    {
        old_num_con = num_con;

        for ( int32_t i = 0 ; i < N ; ++i )
        {
            // Predict the result of the ith training example
            result = m_model->argmax(m_w, i);

            // Compute the loss associated with the prediction
            slack = m_loss->loss( compute_loss_arg(result) );
            cur_list = (CList*) results->get_element(i);

            // Update the list of constraints
            if ( cur_list->get_num_elements() > 0 )
            {
                // Find the maximum loss within the elements of
                // the list of constraints
                cur_res = (CResultSet*) cur_list->get_first_element();
                max_slack = -CMath::INFTY;

                while ( cur_res != NULL )
                {
                    max_slack = CMath::max(max_slack,
                            m_loss->loss( compute_loss_arg(cur_res) ));

                    SG_UNREF(cur_res);
                    cur_res = (CResultSet*) cur_list->get_next_element();
                }

                if ( slack > max_slack )
                {
                    // The current training example is a
                    // violated constraint
                    if ( ! insert_result(cur_list, result) )
                    {
                        exception = true;
                        break;
                    }

                    add_constraint(mosek, result, num_con, i);
                    ++num_con;
                }
            }
            else
            {
                // First iteration of do ... while, add constraint
                if ( ! insert_result(cur_list, result) )
                {
                    exception = true;
                    break;
                }

                add_constraint(mosek, result, num_con, i);
                ++num_con;
            }

            SG_UNREF(cur_list);
            SG_UNREF(result);
        }

        // Solve the QP
        mosek->optimize(sol);
        for ( int32_t i = 0 ; i < M+num_aux+N ; ++i )
        {
            if ( i < M )
                m_w[i] = sol[i];
            else if ( i < M+num_aux )
                aux[i-M] = sol[i];
            else
                m_slacks[i-M-num_aux] = sol[i];
        }

    } while ( old_num_con != num_con && ! exception );

    // Free resources
    SG_UNREF(results);
    SG_UNREF(mosek);
    SG_UNREF(model_features);
    return true;
}

float64_t CPrimalMosekSOSVM::compute_loss_arg(CResultSet* result) const
{
    // Dimensionality of the joint feature space
    int32_t M = m_w.vlen;

    return  SGVector< float64_t >::dot(m_w.vector, result->psi_pred.vector, M) +
        result->delta -
        SGVector< float64_t >::dot(m_w.vector, result->psi_truth.vector, M);
}

bool CPrimalMosekSOSVM::insert_result(CList* result_list, CResultSet* result) const
{
    bool succeed = result_list->insert_element(result);

    if ( ! succeed )
    {
        SG_PRINT("ResultSet could not be inserted in the list..."
             "aborting training of PrimalMosekSOSVM\n");
    }

    return succeed;
}

bool CPrimalMosekSOSVM::add_constraint(
        CMosek* mosek,
        CResultSet* result,
        index_t con_idx,
        index_t train_idx) const
{
    int32_t M = m_model->get_dim();
    SGVector< float64_t > dPsi(M);

    for ( int i = 0 ; i < M ; ++i )
        dPsi[i] = result->psi_pred[i] - result->psi_truth[i];

    return ( mosek->add_constraint_sosvm(dPsi, con_idx, train_idx, 
            m_model->get_num_aux(), -result->delta) == MSK_RES_OK );
}

#endif /* USE_MOSEK */