Added a dot() function which can dot a sparse vector with a dense vector.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%404177

dlib/svm/sparse_vector.h

@@ -195,19 +195,16 @@ namespace dlib
 
     // ------------------------------------------------------------------------------------
 
-        template <typename T, typename U>
+        template <typename T>
         typename T::value_type::second_type dot (
             const T& a,
-            const U& b
+            const T& b
         )
         {
             typedef typename T::value_type::second_type scalar_type;
-            typedef typename U::value_type::second_type scalar_typeU;
-            // Both T and U must contain the same kinds of elements
-            COMPILE_TIME_ASSERT((is_same_type<scalar_type, scalar_typeU>::value));
 
             typename T::const_iterator ai = a.begin();
-            typename U::const_iterator bi = b.begin();
+            typename T::const_iterator bi = b.begin();
 
             scalar_type sum = 0;
             while (ai != a.end() && bi != b.end())
@@ -231,6 +228,43 @@ namespace dlib
             return sum;
         }
 
+    // ------------------------------------------------------------------------------------
+
+        template <typename T, typename EXP>
+        typename T::value_type::second_type dot (
+            const T& a,
+            const matrix_exp<EXP>& b
+        )
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(is_vector(b) && max_index_plus_one(a) <= (unsigned long)b.size(),
+                "\t scalar_type dot(sparse_vector a, dense_vector b)"
+                << "\n\t 'b' must be a vector to be used in a dot product and the sparse vector 'a'"
+                << "\n\t can't be bigger that the dense vector 'b'."
+                );
+
+            typedef typename T::value_type::second_type scalar_type;
+
+            scalar_type sum = 0;
+            for (typename T::const_iterator ai = a.begin(); ai != a.end(); ++ai)
+            {
+                sum += ai->second * b(ai->first);
+            }
+
+            return sum;
+        }
+
+    // ------------------------------------------------------------------------------------
+
+        template <typename T, typename EXP>
+        typename T::value_type::second_type dot (
+            const matrix_exp<EXP>& b,
+            const T& a
+        )
+        {
+            return dot(a,b);
+        }
+
     // ------------------------------------------------------------------------------------
 
         template <typename T>

dlib/svm/sparse_vector_abstract.h

@@ -138,15 +138,48 @@ namespace dlib
 
     // ----------------------------------------------------------------------------------------
 
-        template <typename T, typename U>
+        template <typename T>
         typename T::value_type::second_type dot (
             const T& a,
-            const U& b
+            const T& b
         );
         /*!
             requires
-                - a is a sorted range of std::pair objects
+                - a and b are valid sparse vectors (as defined at the top of this file).
-                - b is a sorted range of std::pair objects
+            ensures
+                - returns the dot product between the vectors a and b
+        !*/
+
+    // ----------------------------------------------------------------------------------------
+
+        template <typename T, typename EXP>
+        typename T::value_type::second_type dot (
+            const T& a,
+            const matrix_exp<EXP>& b
+        );
+        /*!
+            requires
+                - a is a valid sparse vector (as defined at the top of this file).
+                - is_vector(b) == true
+                - max_index_plus_one(a) <= b.size()
+                  (i.e. a can't be bigger than b)
+            ensures
+                - returns the dot product between the vectors a and b
+        !*/
+
+    // ----------------------------------------------------------------------------------------
+
+        template <typename T, typename EXP>
+        typename T::value_type::second_type dot (
+            const matrix_exp<EXP>& a,
+            const T& b
+        );
+        /*!
+            requires
+                - b is a valid sparse vector (as defined at the top of this file).
+                - is_vector(a) == true
+                - max_index_plus_one(b) <= a.size()
+                  (i.e. b can't be bigger than a)
             ensures
                 - returns the dot product between the vectors a and b
         !*/

dlib/svm/svm_c_linear_trainer.h

@@ -152,31 +152,6 @@ namespace dlib
 
     private:
 
-    // -----------------------------------------------------
-    // -----------------------------------------------------
-
-        template <typename EXP>
-        scalar_type dot_helper (
-            const matrix_type& w,
-            const matrix_exp<EXP>& sample
-        ) const
-        {
-            return dot(colm(w,0,sample.size()), sample);
-        }
-
-        template <typename T>
-        typename disable_if<is_matrix<T>,scalar_type >::type dot_helper (
-            const matrix_type& w,
-            const T& sample
-        ) const
-        {
-            // compute a dot product between a dense column vector and a sparse vector
-            scalar_type temp = 0;
-            for (typename T::const_iterator i = sample.begin(); i != sample.end(); ++i)
-                temp += w(i->first) * i->second;
-            return temp;
-        }
-
     // -----------------------------------------------------
     // -----------------------------------------------------
 
@@ -189,9 +164,9 @@ namespace dlib
                 - for all i: #dot_prods[i] == dot(colm(#w,0,w.size()-1), samples(i)) - #w(w.size()-1)
         !*/
         {
-
+            using sparse_vector::dot;
             for (long i = 0; i < samples.size(); ++i)
-                dot_prods[i] = dot_helper(w,samples(i)) - w(w.size()-1);
+                dot_prods[i] = dot(colm(w,0,w.size()-1), samples(i)) - w(w.size()-1);
 
             if (is_first_call)
             {

dlib/test/svm_c_linear.cpp

@@ -163,6 +163,23 @@ namespace
         DLIB_TEST(m(1) == 1 - 2*samples[3][1].second);
         DLIB_TEST(m(2) == 1);
 
+        // test mixed sparse and dense dot products
+        {
+            std::map<unsigned int, double> sv;
+            matrix<double,0,1> dv(4);
+
+            dv = 1,2,3,4;
+
+            sv[0] = 1;
+            sv[3] = 1;
+
+            using namespace sparse_vector;
+
+            DLIB_TEST(dot(sv,dv) == 5);
+            DLIB_TEST(dot(dv,sv) == 5);
+            DLIB_TEST(dot(dv,dv) == 30);
+            DLIB_TEST(dot(sv,sv) == 2);
+        }
     }
 
 // ----------------------------------------------------------------------------------------
@@ -202,10 +219,10 @@ namespace
 
 // ----------------------------------------------------------------------------------------
 
-    class svm_c_linear_tester : public tester
+    class tester_svm_c_linear : public tester
     {
     public:
-        svm_c_linear_tester (
+        tester_svm_c_linear (
         ) :
             tester ("test_svm_c_linear",
                     "Runs tests on the svm_c_linear_trainer.")