fusion find_if loop unrolling and use of advance optimization for random traversal sequences

[SVN r37856]

include/boost/fusion/algorithm/query/detail/find_if.hpp

@@ -1,5 +1,6 @@
 /*=============================================================================
     Copyright (c) 2001-2006 Joel de Guzman
+    Copyright (c) 2007 Dan Marsden
 
     Distributed under the Boost Software License, Version 1.0. (See accompanying 
     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -16,18 +17,22 @@
 #include <boost/fusion/iterator/equal_to.hpp>
 #include <boost/fusion/iterator/next.hpp>
 #include <boost/fusion/sequence/intrinsic/begin.hpp>
+#include <boost/fusion/iterator/advance.hpp>
+#include <boost/fusion/iterator/distance.hpp>
+#include <boost/fusion/support/category_of.hpp>
+#include <boost/mpl/eval_if.hpp>
+#include <boost/mpl/identity.hpp>
 
-namespace boost { namespace fusion { namespace detail
+namespace boost { namespace fusion { 
+    struct random_access_traversal_tag;
+namespace detail
 {
     template <typename Iterator, typename Pred>
     struct apply_filter
     {
-        typedef typename
+        typedef typename mpl::apply1<
-            mpl::apply1<
+            Pred, typename result_of::value_of<Iterator>::type>::type type;
-                Pred
+        BOOST_STATIC_CONSTANT(int, value = type::value);
-              , typename result_of::value_of<Iterator>::type
-            >::type
-        type;
     };
 
     template <typename First, typename Last, typename Pred>
@@ -60,37 +65,166 @@ namespace boost { namespace fusion { namespace detail
         type;
     };
 
+    template<
+        typename First, typename Last, 
+        typename Pred, bool>
+    struct choose_find_if;
+
+    template<typename First, typename Last, typename Pred>
+    struct choose_find_if<First, Last, Pred, false>
+        : main_find_if<First, Last, Pred>
+    {};
+
+    template<typename Iter, typename Pred, int n, int unrolling>
+    struct unroll_again;
+
+    template <typename Iter, typename Pred, int offset>
+    struct apply_offset_filter
+    {
+        typedef typename result_of::advance_c<Iter, offset>::type Shifted;
+        typedef typename
+            mpl::apply1<
+                Pred
+              , typename result_of::value_of<Shifted>::type
+            >::type
+        type;
+        BOOST_STATIC_CONSTANT(int, value = type::value);
+    };
+
+    template<typename Iter, typename Pred, int n>
+    struct unrolled_find_if
+    {
+        typedef typename mpl::eval_if<
+            apply_filter<Iter, Pred>,
+            mpl::identity<Iter>,
+            mpl::eval_if<
+              apply_offset_filter<Iter, Pred, 1>,
+              result_of::advance_c<Iter, 1>,
+              mpl::eval_if<
+                apply_offset_filter<Iter, Pred, 2>,
+                result_of::advance_c<Iter, 2>,
+                mpl::eval_if<
+                  apply_offset_filter<Iter, Pred, 3>,
+                  result_of::advance_c<Iter, 3>,
+                  unroll_again<
+                    Iter,
+                    Pred,
+                    n,
+                    4> > > > >::type type;
+    };
+
+    template<typename Iter, typename Pred>
+    struct unrolled_find_if<Iter, Pred, 3>
+    {
+        typedef typename mpl::eval_if<
+            apply_filter<Iter, Pred>,
+            mpl::identity<Iter>,
+            mpl::eval_if<
+              apply_offset_filter<Iter, Pred, 1>,
+              result_of::advance_c<Iter, 1>,
+              mpl::eval_if<
+                apply_offset_filter<Iter, Pred, 2>,
+                result_of::advance_c<Iter, 2>,
+                result_of::advance_c<Iter, 3> > > >::type type;
+    };
+
+    template<typename Iter, typename Pred>
+    struct unrolled_find_if<Iter, Pred, 2>
+    {
+        typedef typename mpl::eval_if<
+            apply_filter<Iter, Pred>,
+            mpl::identity<Iter>,
+            mpl::eval_if<
+              apply_offset_filter<Iter, Pred, 1>,
+              result_of::advance_c<Iter, 1>,
+              result_of::advance_c<Iter, 2> > >::type type;
+    };
+
+    template<typename Iter, typename Pred>
+    struct unrolled_find_if<Iter, Pred, 1>
+    {
+        typedef typename mpl::eval_if<
+            apply_filter<Iter, Pred>,
+            mpl::identity<Iter>,
+            result_of::advance_c<Iter, 1> >::type type;
+    };
+
+    template<typename Iter, typename Pred, int n, int unrolling>
+    struct unroll_again
+    {
+        typedef typename unrolled_find_if<
+            typename result_of::advance_c<Iter, unrolling>::type,
+            Pred,
+            n-unrolling>::type type;
+    };
+
+    template<typename Iter, typename Pred>
+    struct unrolled_find_if<Iter, Pred, 0>
+    {
+        typedef Iter type;
+    };
+
+    template<typename First, typename Last, typename Pred>
+    struct choose_find_if<First, Last, Pred, true>
+    {
+        typedef typename result_of::distance<First, Last>::type N;
+        typedef typename unrolled_find_if<First, Pred, N::value>::type type;
+    };
+
     template <typename First, typename Last, typename Pred>
     struct static_find_if
     {
         typedef typename
-            main_find_if<
+            choose_find_if<
                 First
               , Last
               , typename mpl::lambda<Pred>::type
+              , is_base_of<random_access_traversal_tag, typename traits::category_of<First>::type>::value
             >::type
         type;
 
         template <typename Iterator>
         static type
-        call(Iterator const& iter, mpl::true_)
+        recursive_call(Iterator const& iter, mpl::true_)
         {
             return iter;
         }
 
         template <typename Iterator>
         static type
-        call(Iterator const& iter, mpl::false_)
+        recursive_call(Iterator const& iter, mpl::false_)
         {
-            return call(fusion::next(iter));
+            return recursive_call(fusion::next(iter));
+        }
+
+        template <typename Iterator>
+        static type
+        recursive_call(Iterator const& iter)
+        {
+            typedef result_of::equal_to<Iterator, type> found;
+            return recursive_call(iter, found());
+        }
+
+        template <typename Iterator, typename Tag>
+        static type
+        choose_call(Iterator const& iter, Tag)
+        {
+            return recursive_call(iter);
+        }
+
+        template <typename Iterator>
+        static type
+        choose_call(Iterator const& iter, random_access_traversal_tag)
+        {
+            typedef typename result_of::distance<Iterator, type>::type N;
+            return fusion::advance<N>(iter);
         }
 
         template <typename Iterator>
         static type
         call(Iterator const& iter)
         {
-            typedef result_of::equal_to<Iterator, type> found;
+            return choose_call(iter, typename traits::category_of<Iterator>::type());
-            return call(iter, found());
         }
     };