issue #76: added cds::atomicity::cache_friendly_item_counter to avoid false sharing

[libcds.git] / cds / container / michael_map.h

diff --git a/cds/container/michael_map.h b/cds/container/michael_map.h
index 22b2dccf8ed6898c650b04dc3da83192edab55a6..9f851f696d8fefc1d5d76b350b87b9586245e780 100644 (file)
--- a/cds/container/michael_map.h
+++ b/cds/container/michael_map.h
@@ -171,10 +171,6 @@ namespace cds { namespace container {
         // GC and OrderedList::gc must be the same
         static_assert( std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
 
-        // atomicity::empty_item_counter is not allowed as a item counter
-        static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
-                        "atomicity::empty_item_counter is not allowed as a item counter");
-
         static CDS_CONSTEXPR const size_t c_nHazardPtrCount = ordered_list::c_nHazardPtrCount; ///< Count of hazard pointer required
 
         //@cond
@@ -194,8 +190,8 @@ namespace cds { namespace container {
         //@cond
         const size_t            m_nHashBitmask;
         internal_bucket_type*   m_Buckets;     ///< bucket table
-        item_counter            m_ItemCounter; ///< Item counter
         hash                    m_HashFunctor; ///< Hash functor
+        item_counter            m_ItemCounter; ///< Item counter
         stat                    m_Stat;        ///< Internal statistics
         //@endcond
 
@@ -920,8 +916,8 @@ namespace cds { namespace container {
 
         /// Checks if the map is empty
         /**
-            Emptiness is checked by item counting: if item count is zero then the map is empty.
-            Thus, the correct item counting is an important part of the map implementation.
+            @warning If you use \p atomicity::empty_item_counter in \p traits::item_counter,
+            the function always returns \p true.
         */
         bool empty() const
         {
@@ -929,6 +925,10 @@ namespace cds { namespace container {
         }
 
         /// Returns item count in the map
+        /**
+            If you use \p atomicity::empty_item_counter in \p traits::item_counter,
+            the function always returns 0.
+        */
         size_t size() const
         {
             return m_ItemCounter;