    // Copyright (C) 2011  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_CROSS_VALIDATE_SEQUENCE_LABeLER_H__
    #define DLIB_CROSS_VALIDATE_SEQUENCE_LABeLER_H__

    #include "cross_validate_sequence_labeler_abstract.h"
    #include <vector>
    #include "../matrix.h"
    #include "svm.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        template <
            typename sequence_labeler_type,
            typename sequence_type
            >
        const matrix<double> test_sequence_labeler (
            const sequence_labeler_type& labeler,
            const std::vector<sequence_type>& samples,
            const std::vector<std::vector<unsigned long> >& labels
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT( is_sequence_labeling_problem(samples, labels) == true,
                        "\tmatrix test_sequence_labeler()"
                        << "\n\t invalid inputs were given to this function"
                        << "\n\t is_sequence_labeling_problem(samples, labels): "
                        << is_sequence_labeling_problem(samples, labels));

            matrix<double> res(labeler.num_labels(), labeler.num_labels());
            res = 0;

            std::vector<unsigned long> pred;
            for (unsigned long i = 0; i < samples.size(); ++i)
            {
                labeler.label_sequence(samples[i], pred);

                for (unsigned long j = 0; j < pred.size(); ++j)
                {
                    const unsigned long truth = labels[i][j];
                    if (truth >= static_cast<unsigned long>(res.nr()))
                    {
                        // ignore labels the labeler doesn't know about.
                        continue;
                    }

                    res(truth, pred[j]) += 1;
                }
            }

            return res;
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename trainer_type,
            typename sequence_type
            >
        const matrix<double> cross_validate_sequence_labeler (
            const trainer_type& trainer,
            const std::vector<sequence_type>& samples,
            const std::vector<std::vector<unsigned long> >& labels,
            const long folds
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(is_sequence_labeling_problem(samples,labels) == true &&
                        1 < folds && folds <= static_cast<long>(samples.size()),
                "\tmatrix cross_validate_sequence_labeler()"
                << "\n\t invalid inputs were given to this function"
                << "\n\t samples.size(): " << samples.size()
                << "\n\t folds:  " << folds
                << "\n\t is_sequence_labeling_problem(samples,labels): " << is_sequence_labeling_problem(samples,labels)
                );

    #ifdef ENABLE_ASSERTS
            for (unsigned long i = 0; i < labels.size(); ++i)
            {
                for (unsigned long j = 0; j < labels[i].size(); ++j)
                {
                    // make sure requires clause is not broken
                    DLIB_ASSERT(labels[i][j] < trainer.num_labels(),
                                "\t matrix cross_validate_sequence_labeler()"
                                << "\n\t The labels are invalid."
                                << "\n\t labels[i][j]: " << labels[i][j]
                                << "\n\t trainer.num_labels(): " << trainer.num_labels()
                                << "\n\t i: " << i
                                << "\n\t j: " << j
                    );
                }
            }
    #endif

            const long num_in_test = samples.size()/folds;
            const long num_in_train = samples.size() - num_in_test;

            std::vector<sequence_type> x_test, x_train;
            std::vector<std::vector<unsigned long> > y_test, y_train;

            long next_test_idx = 0;

            matrix<double> res;

            for (long i = 0; i < folds; ++i)
            {
                x_test.clear();
                y_test.clear();
                x_train.clear();
                y_train.clear();

                // load up the test samples
                for (long cnt = 0; cnt < num_in_test; ++cnt)
                {
                    x_test.push_back(samples[next_test_idx]);
                    y_test.push_back(labels[next_test_idx]);
                    next_test_idx = (next_test_idx + 1)%samples.size();
                }

                // load up the training samples
                long next = next_test_idx;
                for (long cnt = 0; cnt < num_in_train; ++cnt)
                {
                    x_train.push_back(samples[next]);
                    y_train.push_back(labels[next]);
                    next = (next + 1)%samples.size();
                }

                res += test_sequence_labeler(trainer.train(x_train,y_train), x_test, y_test);

            } // for (long i = 0; i < folds; ++i)

            return res;
        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_CROSS_VALIDATE_SEQUENCE_LABeLER_H__