dlib C++ Library - assignment_function.h

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

    #include "assignment_function_abstract.h"
    #include "../matrix.h"
    #include <vector>
    #include "../optimization/max_cost_assignment.h"

    namespace dlib
    {

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

        template <
            typename feature_extractor
            >
        class assignment_function
        {
        public:

            typedef typename feature_extractor::lhs_element lhs_element;
            typedef typename feature_extractor::rhs_element rhs_element;

            typedef std::pair<std::vector<lhs_element>, std::vector<rhs_element> > sample_type;

            typedef std::vector<long> label_type;
            typedef label_type result_type;

            assignment_function()
            {
                weights.set_size(fe.num_features());
                weights = 0;
                bias = 0;
                force_assignment = false;
            }

            explicit assignment_function(
                const matrix<double,0,1>& weights_,
                double bias_
            ) :
                weights(weights_),
                bias(bias_),
                force_assignment(false)
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(fe.num_features() == static_cast<unsigned long>(weights_.size()),
                    "\t assignment_function::assignment_function(weights_)"
                    << "\n\t These sizes should match"
                    << "\n\t fe.num_features(): " << fe.num_features()
                    << "\n\t weights_.size():   " << weights_.size()
                    << "\n\t this: " << this
                    );

            }

            assignment_function(
                const matrix<double,0,1>& weights_,
                double bias_,
                const feature_extractor& fe_
            ) :
                fe(fe_),
                weights(weights_),
                bias(bias_),
                force_assignment(false)
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(fe_.num_features() == static_cast<unsigned long>(weights_.size()),
                    "\t assignment_function::assignment_function(weights_,fe_)"
                    << "\n\t These sizes should match"
                    << "\n\t fe_.num_features(): " << fe_.num_features()
                    << "\n\t weights_.size():    " << weights_.size()
                    << "\n\t this: " << this
                    );
            }

            assignment_function(
                const matrix<double,0,1>& weights_,
                double bias_,
                const feature_extractor& fe_,
                bool force_assignment_
            ) :
                fe(fe_),
                weights(weights_),
                bias(bias_),
                force_assignment(force_assignment_)
            {
                // make sure requires clause is not broken
                DLIB_ASSERT(fe_.num_features() == static_cast<unsigned long>(weights_.size()),
                    "\t assignment_function::assignment_function(weights_,fe_,force_assignment_)"
                    << "\n\t These sizes should match"
                    << "\n\t fe_.num_features(): " << fe_.num_features()
                    << "\n\t weights_.size():    " << weights_.size()
                    << "\n\t this: " << this
                    );
            }

            const feature_extractor& get_feature_extractor (
            ) const { return fe; }

            const matrix<double,0,1>& get_weights (
            ) const { return weights; }

            double get_bias (
            ) const { return bias; }

            bool forces_assignment (
            ) const { return force_assignment; }

            void predict_assignments (
                const std::vector<lhs_element>& lhs,
                const std::vector<rhs_element>& rhs,
                result_type& assignment
            ) const
            {
                assignment.clear();

                matrix<double> cost;
                unsigned long size;
                if (force_assignment)
                {
                    size = std::max(lhs.size(), rhs.size());
                }
                else
                {
                    size = rhs.size() + lhs.size();
                }
                cost.set_size(size, size);

                typedef typename feature_extractor::feature_vector_type feature_vector_type;
                feature_vector_type feats;

                // now fill out the cost assignment matrix
                for (long r = 0; r < cost.nr(); ++r)
                {
                    for (long c = 0; c < cost.nc(); ++c)
                    {
                        if (r < (long)lhs.size() && c < (long)rhs.size())
                        {
                            fe.get_features(lhs[r], rhs[c], feats);
                            cost(r,c) = dot(weights, feats) + bias;
                        }
                        else
                        {
                            cost(r,c) = 0;
                        }
                    }
                }

                if (cost.size() != 0)
                {
                    // max_cost_assignment() only works with integer matrices, so convert from
                    // double to integer.
                    const double scale = static_cast<double>(std::numeric_limits<dlib::int64>::max())/1000/max(abs(cost));
                    matrix<dlib::int64> int_cost = matrix_cast<dlib::int64>(round(cost*scale));
                    assignment = max_cost_assignment(int_cost);
                    assignment.resize(lhs.size());
                }

                // adjust assignment so that non-assignments have a value of -1
                for (unsigned long i = 0; i < assignment.size(); ++i)
                {
                    if (assignment[i] >= (long)rhs.size())
                        assignment[i] = -1;
                }
            }

            void predict_assignments (
                const sample_type& item,
                result_type& assignment
            ) const
            {
                predict_assignments(item.first, item.second, assignment);
            }

            result_type operator()(
                const std::vector<lhs_element>& lhs,
                const std::vector<rhs_element>& rhs
            ) const
            {
                result_type temp;
                predict_assignments(lhs,rhs,temp);
                return temp;
            }

            result_type operator() (
                const sample_type& item
            ) const
            {
                return (*this)(item.first, item.second);
            }

        private:

            feature_extractor fe;
            matrix<double,0,1> weights;
            double bias;
            bool force_assignment;
        };

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

        template <
            typename feature_extractor
            >
        void serialize (
            const assignment_function<feature_extractor>& item,
            std::ostream& out
        )
        {
            int version = 2;
            serialize(version, out);
            serialize(item.get_feature_extractor(), out);
            serialize(item.get_weights(), out);
            serialize(item.get_bias(), out);
            serialize(item.forces_assignment(), out);
        }

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

        template <
            typename feature_extractor
            >
        void deserialize (
            assignment_function<feature_extractor>& item,
            std::istream& in
        )
        {
            feature_extractor fe;
            matrix<double,0,1> weights;
            double bias;
            bool force_assignment;
            int version = 0;
            deserialize(version, in);
            if (version != 2)
                throw serialization_error("Unexpected version found while deserializing dlib::assignment_function.");

            deserialize(fe, in);
            deserialize(weights, in);
            deserialize(bias, in);
            deserialize(force_assignment, in);

            item = assignment_function<feature_extractor>(weights, bias, fe, force_assignment);
        }

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

    }

    #endif // DLIB_ASSIGNMENT_FuNCTION_Hh_