From efb1a12dc4cf5e747b38689b406388d2cb1f9d07 Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Sun, 6 May 2012 11:51:18 -0400
Subject: [PATCH] Added the ability for the user to set the per class loss.

---
 .../structural_svm_graph_labeling_problem.h   | 50 +++++++++++++++++--
 ...ural_svm_graph_labeling_problem_abstract.h | 40 +++++++++++++++
 2 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/dlib/svm/structural_svm_graph_labeling_problem.h b/dlib/svm/structural_svm_graph_labeling_problem.h
index 36c290a09..79b490e97 100644
--- a/dlib/svm/structural_svm_graph_labeling_problem.h
+++ b/dlib/svm/structural_svm_graph_labeling_problem.h
@@ -149,6 +149,8 @@ namespace dlib
                     << "\n\t labels.size():  " << labels.size() 
                     << "\n\t this: " << this );
 
+            loss_pos = 1.0;
+            loss_neg = 1.0;
 
             // figure out how many dimensions are in the node and edge vectors.
             node_dims = 0;
@@ -172,6 +174,41 @@ namespace dlib
             return edge_dims;
         }
 
+        void set_loss_on_positive_class (
+            double loss
+        )
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(loss >= 0,
+                    "\t structural_svm_graph_labeling_problem::set_loss_on_positive_class()"
+                    << "\n\t Invalid inputs were given to this function."
+                    << "\n\t loss: " << loss 
+                    << "\n\t this: " << this );
+
+            loss_pos = loss;
+        }
+
+        void set_loss_on_negative_class (
+            double loss
+        )
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(loss >= 0,
+                    "\t structural_svm_graph_labeling_problem::set_loss_on_negative_class()"
+                    << "\n\t Invalid inputs were given to this function."
+                    << "\n\t loss: " << loss 
+                    << "\n\t this: " << this );
+
+            loss_pos = loss;
+        }
+
+        double get_loss_on_negative_class (
+        ) const { return loss_neg; }
+
+        double get_loss_on_positive_class (
+        ) const { return loss_pos; }
+
+
     private:
         virtual long get_num_dimensions (
         ) const 
@@ -303,9 +340,9 @@ namespace dlib
                 // max when we use find_max_factor_graph_potts() below.
                 const bool label_i = (labels[idx][i]!=0);
                 if (label_i)
-                    g.node(i).data -= 1.0;
+                    g.node(i).data -= loss_pos;
                 else
-                    g.node(i).data += 1.0;
+                    g.node(i).data += loss_neg;
 
                 for (unsigned long n = 0; n < g.node(i).number_of_neighbors(); ++n)
                 {
@@ -331,7 +368,12 @@ namespace dlib
                 const bool true_label = (labels[idx][i]!= 0);
                 const bool pred_label = (labeling[i]!= 0);
                 if (true_label != pred_label)
-                    ++loss;
+                {
+                    if (true_label == true)
+                        loss += loss_pos;
+                    else
+                        loss += loss_neg;
+                }
             }
 
             // compute psi
@@ -343,6 +385,8 @@ namespace dlib
 
         long node_dims;
         long edge_dims;
+        double loss_pos;
+        double loss_neg;
     };
 
 // ----------------------------------------------------------------------------------------
diff --git a/dlib/svm/structural_svm_graph_labeling_problem_abstract.h b/dlib/svm/structural_svm_graph_labeling_problem_abstract.h
index a18abbc2c..8241b9cc3 100644
--- a/dlib/svm/structural_svm_graph_labeling_problem_abstract.h
+++ b/dlib/svm/structural_svm_graph_labeling_problem_abstract.h
@@ -120,6 +120,46 @@ namespace dlib
                   part of the total weight vector.  You can do this by passing get_num_edge_weights()
                   to the third argument to oca::operator().
         !*/
+
+        void set_loss_on_positive_class (
+            double loss
+        );
+        /*!
+            requires
+                - loss >= 0
+            ensures
+                - #get_loss_on_positive_class() == loss
+        !*/
+
+        void set_loss_on_negative_class (
+            double loss
+        );
+        /*!
+            requires
+                - loss >= 0
+            ensures
+                - #get_loss_on_negative_class() == loss
+        !*/
+
+        double get_loss_on_positive_class (
+        ) const;
+        /*!
+            ensures
+                - returns the loss incurred when a graph node which is supposed to have
+                  a label of true gets misclassified.  This value controls how much we care 
+                  about correctly classifying nodes which should be labeled as true.  Larger 
+                  loss values indicate that we care more strongly than smaller values.
+        !*/
+
+        double get_loss_on_negative_class (
+        ) const;
+        /*!
+            ensures
+                - returns the loss incurred when a graph node which is supposed to have
+                  a label of false gets misclassified.  This value controls how much we care 
+                  about correctly classifying nodes which should be labeled as false.  Larger 
+                  loss values indicate that we care more strongly than smaller values.
+        !*/
     };
 
 // ----------------------------------------------------------------------------------------