improve the performance of sort<>

brunocodutra · Aug 18, 2016 · a0e9ac5 · a0e9ac5
1 parent f67e991
commit a0e9ac5
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Showing 7 changed files with 103 additions and 342 deletions.
diff --git a/include/metal/list.hpp b/include/metal/list.hpp
@@ -27,15 +27,13 @@
 #include <metal/list/insert.hpp>
 #include <metal/list/join.hpp>
 #include <metal/list/list.hpp>
-#include <metal/list/merge.hpp>
 #include <metal/list/none.hpp>
 #include <metal/list/partition.hpp>
 #include <metal/list/pop_back.hpp>
 #include <metal/list/pop_front.hpp>
 #include <metal/list/push_back.hpp>
 #include <metal/list/push_front.hpp>
 #include <metal/list/range.hpp>
-#include <metal/list/reduce.hpp>
 #include <metal/list/remove.hpp>
 #include <metal/list/remove_if.hpp>
 #include <metal/list/replace.hpp>

diff --git a/include/metal/list/merge.hpp b/include/metal/list/merge.hpp
diff --git a/include/metal/list/reduce.hpp b/include/metal/list/reduce.hpp
diff --git a/include/metal/list/sort.hpp b/include/metal/list/sort.hpp
@@ -5,22 +5,113 @@
 #ifndef METAL_LIST_SORT_HPP
 #define METAL_LIST_SORT_HPP
 
-#include <metal/list/list.hpp>
-#include <metal/list/merge.hpp>
-#include <metal/list/transpose.hpp>
-#include <metal/lambda/apply.hpp>
 #include <metal/lambda/lambda.hpp>
-#include <metal/lambda/partial.hpp>
+#include <metal/number/if.hpp>
 
 namespace metal
 {
+    namespace detail
+    {
+        template<typename seq, typename lbd>
+        struct _sort;
+    }
+
     /// \ingroup list
     /// ...
     template<typename seq, typename lbd>
-    using sort = metal::apply<
-        metal::partial<metal::lambda<metal::merge>, lbd, metal::list<>>,
-        metal::transpose<metal::list<seq>>
-    >;
+    using sort = typename detail::_sort<seq, if_<is_lambda<lbd>, lbd>>::type;
+}
+
+#include <metal/list/list.hpp>
+#include <metal/list/size.hpp>
+#include <metal/list/join.hpp>
+#include <metal/list/range.hpp>
+#include <metal/list/copy_if.hpp>
+#include <metal/list/remove_if.hpp>
+#include <metal/lambda/invoke.hpp>
+#include <metal/lambda/partial.hpp>
+#include <metal/number/number.hpp>
+#include <metal/number/div.hpp>
+
+namespace metal
+{
+    namespace detail
+    {
+        template<typename lbd, typename x, typename y>
+        struct _merge;
+
+        template<typename lbd, typename x, typename y>
+        using merge = typename _merge<lbd, x, y>::type;
+
+        template<typename lbd, typename x, typename xh, typename y, typename yh>
+        using merge_impl = join<
+            remove_if<x, partial<lbd, yh>>,
+            remove_if<y, partial<lbd, xh>>,
+            merge<
+                lbd,
+                copy_if<x, partial<lbd, yh>>,
+                copy_if<y, partial<lbd, xh>>
+            >
+        >;
+
+        template<typename lbd, typename x, typename y>
+        struct _merge
+        {};
+
+        template<
+            typename lbd,
+            typename xh, typename... xt,
+            typename yh, typename... yt
+        >
+        struct _merge<lbd, list<xh, xt...>, list<yh, yt...>> :
+            _invoke<
+                lambda<merge_impl>,
+                lbd, list<xh, xt...>, xh, list<yh, yt...>, yh
+            >
+        {};
+
+        template<typename lbd, typename seq>
+        struct _merge<lbd, seq, list<>>
+        {
+            using type = seq;
+        };
+
+        template<typename lbd, typename seq>
+        struct _merge<lbd, list<>, seq>
+        {
+            using type = seq;
+        };
+
+        template<typename lbd>
+        struct _merge<lbd, list<>, list<>>
+        {
+            using type = list<>;
+        };
+
+        template<typename seq, typename lbd>
+        using sort_impl = merge<
+            lbd,
+            sort<range<seq, number<0>, div<size<seq>, number<2>>>, lbd>,
+            sort<range<seq, div<size<seq>, number<2>>, size<seq>>, lbd>
+        >;
+
+        template<typename seq, typename lbd>
+        struct _sort :
+            _invoke<lambda<sort_impl>, seq, lbd>
+        {};
+
+        template<typename val, typename lbd>
+        struct _sort<list<val>, lbd>
+        {
+            using type = list<val>;
+        };
+
+        template<typename lbd>
+        struct _sort<list<>, lbd>
+        {
+            using type = list<>;
+        };
+    }
 }
 
 #endif
diff --git a/test/src/metal/list/merge.cpp b/test/src/metal/list/merge.cpp