Filled out the spec and added the usual boilerplate for a trainer object.

dlib/svm/structural_assignment_trainer.h

@@ -22,48 +22,195 @@ namespace dlib
     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 assignment_function<feature_extractor> trained_function_type;
 
-        bool forces_assignment(
-        ) const { return false; } // TODO
+        structural_assignment_trainer (
+        )  
+        {
+            set_defaults();
+        }
 
-        const assignment_function<feature_extractor> train (  
-            const std::vector<sample_type>& x,
-            const std::vector<label_type>& y
+        explicit structural_assignment_trainer (
+            const feature_extractor& fe_
+        ) : fe(fe_)
+        {
+            set_defaults();
+        }
+
+        const feature_extractor& get_feature_extractor (
+        ) const { return fe; }
+
+        void set_num_threads (
+            unsigned long num
+        )
+        {
+            num_threads = num;
+        }
+
+        unsigned long get_num_threads (
         ) const
-        /*!
-            requires
-                - is_assignment_problem(x,y) == true
-                - if (force assignment) then
-                    - is_forced_assignment_problem(x,y) == true
-        !*/
         {
-            DLIB_CASSERT(is_assignment_problem(x,y), "");
+            return num_threads;
+        }
+
+        void set_epsilon (
+            double eps_
+        )
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(eps_ > 0,
+                "\t void structural_assignment_trainer::set_epsilon()"
+                << "\n\t eps_ must be greater than 0"
+                << "\n\t eps_: " << eps_ 
+                << "\n\t this: " << this
+                );
+
+            eps = eps_;
+        }
 
-            feature_extractor fe;
+        double get_epsilon (
+        ) const { return eps; }
 
-            bool force_assignment = false;
-            unsigned long num_threads = 1;
-            structural_svm_assignment_problem<feature_extractor> prob(x,y, fe, force_assignment, num_threads);
+        void set_max_cache_size (
+            unsigned long max_size
+        )
+        {
+            max_cache_size = max_size;
+        }
 
-            prob.be_verbose();
-            prob.set_c(50);
-            prob.set_epsilon(1e-10);
-            oca solver;
+        unsigned long get_max_cache_size (
+        ) const
+        {
+            return max_cache_size; 
+        }
+
+        void be_verbose (
+        )
+        {
+            verbose = true;
+        }
+
+        void be_quiet (
+        )
+        {
+            verbose = false;
+        }
+
+        void set_oca (
+            const oca& item
+        )
+        {
+            solver = item;
+        }
+
+        const oca get_oca (
+        ) const
+        {
+            return solver;
+        }
+
+        void set_c (
+            double C_ 
+        )
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(C_ > 0,
+                "\t void structural_assignment_trainer::set_c()"
+                << "\n\t C_ must be greater than 0"
+                << "\n\t C_:    " << C_ 
+                << "\n\t this: " << this
+                );
+
+            C = C_;
+        }
+
+        double get_c (
+        ) const
+        {
+            return C;
+        }
+
+        bool forces_assignment(
+        ) const { return force_assignment; } 
+
+        void set_forces_assignment (
+            bool new_value
+        )
+        {
+            force_assignment = new_value;
+        }
+
+        const assignment_function<feature_extractor> train (  
+            const std::vector<sample_type>& samples,
+            const std::vector<label_type>& labels
+        ) const
+        {
+            // make sure requires clause is not broken
+#ifdef ENABLE_ASSERTS
+            if (force_assignment)
+            {
+                DLIB_ASSERT(is_forced_assignment_problem(samples, labels), 
+                            "\t assignment_function structural_assignment_trainer::train()"
+                            << "\n\t invalid inputs were given to this function"
+                            << "\n\t is_forced_assignment_problem(samples,labels): " << is_forced_assignment_problem(samples,labels)
+                            << "\n\t is_assignment_problem(samples,labels):        " << is_assignment_problem(samples,labels)
+                            << "\n\t is_learning_problem(samples,labels):          " << is_learning_problem(samples,labels)
+                );
+            }
+            else
+            {
+                DLIB_ASSERT(is_assignment_problem(samples, labels),
+                            "\t assignment_function structural_assignment_trainer::train()"
+                            << "\n\t invalid inputs were given to this function"
+                            << "\n\t is_assignment_problem(samples,labels): " << is_assignment_problem(samples,labels)
+                            << "\n\t is_learning_problem(samples,labels):   " << is_learning_problem(samples,labels)
+                );
+            }
+#endif
+
+
+
+            structural_svm_assignment_problem<feature_extractor> prob(samples,labels, fe, force_assignment, num_threads);
+
+            if (verbose)
+                prob.be_verbose();
+
+            prob.set_c(C);
+            prob.set_epsilon(eps);
+            prob.set_max_cache_size(max_cache_size);
 
             matrix<double,0,1> weights; 
 
             solver(prob, weights);
-            std::cout << "weights: "<<  trans(weights) << std::endl;
 
             return assignment_function<feature_extractor>(fe,weights,force_assignment);
 
         }
+
+
+    private:
+
+        bool force_assignment;
+        double C;
+        oca solver;
+        double eps;
+        bool verbose;
+        unsigned long num_threads;
+        unsigned long max_cache_size;
+
+        void set_defaults ()
+        {
+            force_assignment = false;
+            C = 100;
+            verbose = false;
+            eps = 0.1;
+            num_threads = 2;
+            max_cache_size = 40;
+        }
+
+        feature_extractor fe;
     };
 
 // ----------------------------------------------------------------------------------------

dlib/svm/structural_assignment_trainer_abstract.h

+// Copyright (C) 2011  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#undef DLIB_STRUCTURAL_ASSiGNMENT_TRAINER_ABSTRACT_H__
+#ifdef DLIB_STRUCTURAL_ASSiGNMENT_TRAINER_ABSTRACT_H__
+
+#include "../algs.h"
+#include "structural_svm_assignment_problem.h"
+#include "assignment_function_abstract.h"
+
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename feature_extractor
+        >
+    class structural_assignment_trainer
+    {
+        /*!
+            REQUIREMENTS ON feature_extractor
+                It must be an object that implements an interface compatible with 
+                the example_feature_extractor defined in dlib/svm/assignment_function_abstract.h.
+
+            WHAT THIS OBJECT REPRESENTS
+                This object is a tool for learning to solve the assignment problem based
+                on a set of training data.  The training procedure produces an 
+                assignment_function object which can be used to predict the assignments of
+                new data.
+
+                Note that this is just a convenience wrapper around the 
+                structural_svm_assignment_problem to make it look 
+                similar to all the other trainers in dlib.  
+        !*/
+
+    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 assignment_function<feature_extractor> trained_function_type;
+
+        structural_assignment_trainer (
+        );
+        /*!
+            ensures
+                - #get_c() == 100
+                - this object isn't verbose
+                - #get_epsilon() == 0.1
+                - #get_num_threads() == 2
+                - #get_max_cache_size() == 40
+                - #get_feature_extractor() == a default initialized feature_extractor
+                - #forces_assignment() == false
+        !*/
+
+        explicit structural_assignment_trainer (
+            const feature_extractor& fe
+        );
+        /*!
+            ensures
+                - #get_c() == 100
+                - this object isn't verbose
+                - #get_epsilon() == 0.1
+                - #get_num_threads() == 2
+                - #get_max_cache_size() == 40
+                - #get_feature_extractor() == fe 
+                - #forces_assignment() == false
+        !*/
+
+        const feature_extractor& get_feature_extractor (
+        ) const;
+        /*!
+            ensures
+                - returns the feature extractor used by this object
+        !*/
+
+        void set_num_threads (
+            unsigned long num
+        );
+        /*!
+            ensures
+                - #get_num_threads() == num
+        !*/
+
+        unsigned long get_num_threads (
+        ) const;
+        /*!
+            ensures
+                - returns the number of threads used during training.  You should 
+                  usually set this equal to the number of processing cores on your
+                  machine.
+        !*/
+
+        void set_epsilon (
+            double eps
+        );
+        /*!
+            requires
+                - eps > 0
+            ensures
+                - #get_epsilon() == eps
+        !*/
+
+        double get_epsilon (
+        ) const; 
+        /*!
+            ensures
+                - returns the error epsilon that determines when training should stop.
+                  Smaller values may result in a more accurate solution but take longer 
+                  to train.  You can think of this epsilon value as saying "solve the 
+                  optimization problem until the average number of assignment mistakes per 
+                  training sample is within epsilon of its optimal value".
+        !*/
+
+        void set_max_cache_size (
+            unsigned long max_size
+        );
+        /*!
+            ensures
+                - #get_max_cache_size() == max_size
+        !*/
+
+        unsigned long get_max_cache_size (
+        ) const;
+        /*!
+            ensures
+                - During training, this object basically runs the assignment_function on 
+                  each training sample, over and over.  To speed this up, it is possible to 
+                  cache the results of these invocations.  This function returns the number 
+                  of cache elements per training sample kept in the cache.  Note that a value 
+                  of 0 means caching is not used at all.  
+        !*/
+
+        void be_verbose (
+        );
+        /*!
+            ensures
+                - This object will print status messages to standard out so that a 
+                  user can observe the progress of the algorithm.
+        !*/
+
+        void be_quiet (
+        );
+        /*!
+            ensures
+                - this object will not print anything to standard out
+        !*/
+
+        void set_oca (
+            const oca& item
+        );
+        /*!
+            ensures
+                - #get_oca() == item 
+        !*/
+
+        const oca get_oca (
+        ) const;
+        /*!
+            ensures
+                - returns a copy of the optimizer used to solve the structural SVM problem.  
+        !*/
+
+        void set_c (
+            double C 
+        );
+        /*!
+            requires
+                - C > 0
+            ensures
+                - #get_c() = C
+        !*/
+
+        double get_c (
+        ) const;
+        /*!
+            ensures
+                - returns the SVM regularization parameter.  It is the parameter 
+                  that determines the trade-off between trying to fit the training 
+                  data (i.e. minimize the loss) or allowing more errors but hopefully 
+                  improving the generalization of the resulting assignment_function.  
+                  Larger values encourage exact fitting while smaller values of C may 
+                  encourage better generalization. 
+        !*/
+
+        void set_forces_assignment (
+            bool new_value
+        );
+        /*!
+            ensures
+                - #forces_assignment() == new_value
+        !*/
+
+        bool forces_assignment(
+        ) const; 
+        /*!
+            ensures
+                - returns the value of the forces_assignment() parameter for the
+                  assignment_functions generated by this object.  
+        !*/
+
+        const assignment_function<feature_extractor> train (  
+            const std::vector<sample_type>& samples,
+            const std::vector<label_type>& labels
+        ) const;
+        /*!
+            requires
+                - is_assignment_problem(samples,labels) == true
+                - if (forces_assignment()) then
+                    - is_forced_assignment_problem(samples,labels) == true
+            ensures
+                - Uses the structural_svm_assignment_problem to train an 
+                  assignment_function on the given samples/labels training pairs.  
+                  The idea is to learn to predict a label given an input sample.
+                - returns a function F with the following properties:
+                    - F(new_sample) == A set of assignments indicating how the elements of 
+                      new_sample.first match up with the elements of new_sample.second.
+                    - F.forces_assignment() == forces_assignment()
+                    - F.get_feature_extractor() == get_feature_extractor()
+        !*/
+    };
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_STRUCTURAL_ASSiGNMENT_TRAINER_ABSTRACT_H__