From 2932d6d3f4b4d698d51d2c7c94d4090534eaa279 Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Wed, 22 Dec 2010 23:06:55 +0000
Subject: [PATCH] Fixed a minor bug and did some cleanup

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%404014
---
 dlib/svm/svm_c_trainer.h | 76 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 72 insertions(+), 4 deletions(-)

diff --git a/dlib/svm/svm_c_trainer.h b/dlib/svm/svm_c_trainer.h
index c325dce15..306305ab4 100644
--- a/dlib/svm/svm_c_trainer.h
+++ b/dlib/svm/svm_c_trainer.h
@@ -6,7 +6,6 @@
 //#include "local/make_label_kernel_matrix.h"
 
 #include "svm_c_trainer_abstract.h"
-#include "calculate_rho_and_b.h"
 #include <cmath>
 #include <limits>
 #include <sstream>
@@ -236,8 +235,8 @@ namespace dlib
                    alpha,
                    eps);
 
-            scalar_type rho, b;
-            calculate_rho_and_b(y,alpha,solver.get_gradient(),rho,b);
+            scalar_type b;
+            calculate_b(y,alpha,solver.get_gradient(),Cpos,Cneg,b);
             alpha = pointwise_multiply(alpha,y);
 
             // count the number of support vectors
@@ -263,11 +262,80 @@ namespace dlib
             }
 
             // now return the decision function
-            return decision_function<K> (sv_alpha, b*rho, kernel_function, support_vectors);
+            return decision_function<K> (sv_alpha, b, kernel_function, support_vectors);
         }
 
     // ------------------------------------------------------------------------------------
 
+        template <
+            typename scalar_vector_type,
+            typename scalar_vector_type2
+            >
+        void calculate_b(
+            const scalar_vector_type2& y,
+            const scalar_vector_type& alpha,
+            const scalar_vector_type& df,
+            const scalar_type& Cpos,
+            const scalar_type& Cneg,
+            scalar_type& b
+        ) const
+        {
+            using namespace std;
+            long num_free = 0;
+            scalar_type sum_free = 0;
+
+            scalar_type upper_bound = -numeric_limits<scalar_type>::infinity();
+            scalar_type lower_bound = numeric_limits<scalar_type>::infinity();
+
+            for(long i = 0; i < alpha.nr(); ++i)
+            {
+                if(y(i) == 1)
+                {
+                    if(alpha(i) == Cpos)
+                    {
+                        if (df(i) > upper_bound)
+                            upper_bound = df(i);
+                    }
+                    else if(alpha(i) == 0)
+                    {
+                        if (df(i) < lower_bound)
+                            lower_bound = df(i);
+                    }
+                    else
+                    {
+                        ++num_free;
+                        sum_free += df(i);
+                    }
+                }
+                else
+                {
+                    if(alpha(i) == Cneg)
+                    {
+                        if (-df(i) > upper_bound)
+                            upper_bound = -df(i);
+                    }
+                    else if(alpha(i) == 0)
+                    {
+                        if (-df(i) < lower_bound)
+                            lower_bound = -df(i);
+                    }
+                    else
+                    {
+                        ++num_free;
+                        sum_free -= df(i);
+                    }
+                }
+            }
+
+            if(num_free > 0)
+                b = sum_free/num_free;
+            else
+                b = (upper_bound+lower_bound)/2;
+        }
+
+    // ------------------------------------------------------------------------------------
+
+
         kernel_type kernel_function;
         scalar_type Cpos;
         scalar_type Cneg;