It occurred to me that in some cases it is very easy to end up with dense vectors

which are slightly smaller than their corresponding sparse vectors.  So I changed
the requires clause of the dot(sparse,dense) and dot(dense,sparse) functions to not
require that the dense vector's size > sparse vector's size.  Now any combination
of sizes is legal.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%404181

dlib/svm/sparse_vector.h

@@ -258,16 +258,18 @@ namespace dlib
         )
         {
             // make sure requires clause is not broken
-            DLIB_ASSERT(is_vector(b) && max_index_plus_one(a) <= (unsigned long)b.size(),
+            DLIB_ASSERT(is_vector(b),
                 "\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'."
+                << "\n\t 'b' must be a vector to be used in a dot product." 
                 );
 
             typedef typename T::value_type::second_type scalar_type;
+            typedef typename T::value_type::first_type first_type;
 
             scalar_type sum = 0;
-            for (typename T::const_iterator ai = a.begin(); ai != a.end(); ++ai)
+            for (typename T::const_iterator ai = a.begin(); 
+                 (ai != a.end()) && (ai->first < static_cast<first_type>(b.size())); 
+                 ++ai)
             {
                 sum += ai->second * b(ai->first);
             }

dlib/svm/sparse_vector_abstract.h

@@ -159,8 +159,6 @@ namespace dlib
             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
         !*/
@@ -176,8 +174,6 @@ namespace dlib
             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/test/svm_c_linear.cpp

@@ -233,6 +233,9 @@ namespace
                 DLIB_TEST(dot(dv,sv) == 5);
                 DLIB_TEST(dot(dv,dv) == 30);
                 DLIB_TEST(dot(sv,sv) == 2);
+
+                sv[10] = 9;
+                DLIB_TEST(dot(sv,dv) == 5);
             }
 
             // test mixed sparse dense assignments