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

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

diff --git a/cds/container/michael_set_rcu.h b/cds/container/michael_set_rcu.h
index 9733f4c9fa8bf5c00f029b34620cb7a70c46fc7d..34bc0c2bbf33058f4153cdcbffc8a2cb5d6ee947 100644 (file)
--- a/cds/container/michael_set_rcu.h
+++ b/cds/container/michael_set_rcu.h
@@ -1,7 +1,7 @@
 /*
     This file is a part of libcds - Concurrent Data Structures library
 
-    (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
+    (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
 
     Source code repo: http://github.com/khizmax/libcds/
     Download: http://sourceforge.net/projects/libcds/files/
@@ -159,9 +159,6 @@ 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");
 
-        static_assert(!std::is_same<item_counter, atomicity::empty_item_counter>::value,
-            "atomicity::empty_item_counter is not allowed as a item counter");
-
         //@cond
         typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
 
@@ -192,9 +189,9 @@ namespace cds { namespace container {
         typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
 
         const size_t            m_nHashBitmask;
-        item_counter            m_ItemCounter; ///< Item counter
         hash                    m_HashFunctor; ///< Hash functor
         internal_bucket_type*   m_Buckets;     ///< bucket table
+        item_counter            m_ItemCounter; ///< Item counter
         stat                    m_Stat;        ///< Internal statistics
         //@endcond
 
@@ -302,7 +299,7 @@ namespace cds { namespace container {
             size_t nMaxItemCount,   ///< estimation of max item count in the hash set
             size_t nLoadFactor      ///< load factor: estimation of max number of items in the bucket
         ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
-          , m_Buckets( bucket_table_allocator().allocate( bucket_count()) )
+          , m_Buckets( bucket_table_allocator().allocate( bucket_count()))
         {
             for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
                 construct_bucket<bucket_stat>( it );
@@ -743,8 +740,8 @@ namespace cds { namespace container {
 
         /// Checks if the set is empty
         /**
-            Emptiness is checked by item counting: if item count is zero then the set is empty.
-            Thus, the correct item counting feature is an important part of Michael's set implementation.
+            @warning If you use \p atomicity::empty_item_counter in \p traits::item_counter,
+            the function always returns \p true.
         */
         bool empty() const
         {
@@ -752,6 +749,10 @@ namespace cds { namespace container {
         }
 
         /// Returns item count in the set
+        /**
+            @warning 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;