Added an overload of sparse_matrix_vector_multiply() that multiplies a dense

matrix with a sparse vector.

dlib/svm/sparse_vector.h

@@ -1003,10 +1003,60 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
-}
+    template <
+        typename EXP, 
+        typename sparse_vector_type,
+        typename T,
+        long NR,
+        long NC,
+        typename MM,
+        typename L
+        >
+    void sparse_matrix_vector_multiply (
+        const matrix_exp<EXP>& m,
+        const sparse_vector_type& v,
+        matrix<T,NR,NC,MM,L>& result
+    )
+    {
+        // make sure requires clause is not broken
+        DLIB_ASSERT(max_index_plus_one(v) <= (unsigned long)m.nc(),
+                    "\t void sparse_matrix_vector_multiply()"
+                    << "\n\t Invalid inputs were given to this function"
+                    << "\n\t max_index_plus_one(v): " << max_index_plus_one(v)
+                    << "\n\t m.size():              " << m.size() 
+        );
 
-#endif // DLIB_SVm_SPARSE_VECTOR
+        result.set_size(m.nr(),1);
+        result = 0;
 
+        for (typename sparse_vector_type::const_iterator i = v.begin(); i != v.end(); ++i)
+        {
+            for (long r = 0; r < result.nr(); ++r)
+            {
+                result(r) += m(r, i->first)*i->second;
+            }
+        }
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename EXP, 
+        typename sparse_vector_type
+        >
+    matrix<typename EXP::type,0,1> sparse_matrix_vector_multiply (
+        const matrix_exp<EXP>& m,
+        const sparse_vector_type& v
+    )
+    {
+        matrix<typename EXP::type,0,1> result;
+        sparse_matrix_vector_multiply(m,v,result);
+        return result;
+    }
 
+// ----------------------------------------------------------------------------------------
+
+}
 
+#endif // DLIB_SVm_SPARSE_VECTOR
 

dlib/svm/sparse_vector_abstract.h

@@ -618,6 +618,49 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
+    template <
+        typename EXP, 
+        typename sparse_vector_type,
+        typename T,
+        long NR,
+        long NC,
+        typename MM,
+        typename L
+        >
+    void sparse_matrix_vector_multiply (
+        const matrix_exp<EXP>& m,
+        const sparse_vector_type& v,
+        matrix<T,NR,NC,MM,L>& result
+    );
+    /*!
+        requires
+            - max_index_plus_one(v) < m.nc()
+            - v == an unsorted sparse vector
+        ensures
+            - #result == m*v
+              (i.e. multiply m by the vector v and store the output in result)
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename EXP, 
+        typename sparse_vector_type
+        >
+    matrix<typename EXP::type,0,1> sparse_matrix_vector_multiply (
+        const matrix_exp<EXP>& m,
+        const sparse_vector_type& v
+    );
+    /*!
+        requires
+            - max_index_plus_one(v) < m.nc()
+            - v == an unsorted sparse vector
+        ensures
+            - returns m*v
+              (i.e. multiply m by the vector v and return the resulting vector)
+    !*/
+
+// ----------------------------------------------------------------------------------------
 }
 
 #endif // DLIB_SVm_SPARSE_VECTOR_ABSTRACT_