1 /**
2  *
3  *   Copyright (c) 2005-2021 by Pierre-Henri WUILLEMIN(_at_LIP6) & Christophe GONZALES(_at_AMU)
4  *   info_at_agrum_dot_org
5  *
6  *  This library is free software: you can redistribute it and/or modify
7  *  it under the terms of the GNU Lesser General Public License as published by
8  *  the Free Software Foundation, either version 3 of the License, or
9  *  (at your option) any later version.
10  *
11  *  This library is distributed in the hope that it will be useful,
12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  *  GNU Lesser General Public License for more details.
15  *
16  *  You should have received a copy of the GNU Lesser General Public License
17  *  along with this library.  If not, see <http://www.gnu.org/licenses/>.
18  *
19  */
20 
21 
22 /** @file
23  * @brief A wrapper that enables to store data in a way that prevents false
24  * cacheline sharing.
25  *
26  * @author Christophe GONZALES(_at_AMU) and Pierre-Henri WUILLEMIN(_at_LIP6)
27  */
28 #ifndef GUM_THREAD_DATA_H
29 #define GUM_THREAD_DATA_H
30 
31 #include <new>
32 
33 #include <agrum/agrum.h>
34 
35 namespace gum {
36 
37   /** @class ThreadData
38    * @brief A wrapper that enables to store data in a way that prevents false
39    * cacheline sharing.
40    * @headerfile threadData.h <agrum/tools/core/threadData.h>
41    * @ingroup basicstruct_group
42    *
43    * When several threads access to some shared containers like vectors, it
44    * may be the case that they access some data within these containers that
45    * are too close, which results in false sharing of the cacheline. By
46    * wrapping the data into a ThreadData, we guarantee that no false sharing
47    * can occur.
48    *
49    * To create a wrapper data, simply use wrapped_data = ThreadData (data) and
50    * To get the data wrapped, use wrapped_data.data;
51    */
52   template < typename T_DATA >
53   // @TODO: for C++17, replace by
54   // alignas(std::hardware_destructive_interference_size)
55   struct alignas(128) ThreadData {
56     // ##########################################################################
57     /// @name Constructors / Destructors
58     // ##########################################################################
59     /// @{
60 
61     /// default constructor
ThreadDataThreadData62     ThreadData(const T_DATA& theData) : data(theData) {}
63 
64     /// default constructor
ThreadDataThreadData65     ThreadData(T_DATA&& theData) : data(std::move(theData)) {}
66 
67     /// copy constructor
ThreadDataThreadData68     ThreadData(const ThreadData< T_DATA >& from) : data(from.data) {}
69 
70     /// move constructor
ThreadDataThreadData71     ThreadData(ThreadData< T_DATA >&& from) : data(std::move(from.data)) {}
72 
73     /// destructor
~ThreadDataThreadData74     ~ThreadData() {}
75 
76     /// @}
77 
78     // ##########################################################################
79     /// @name Operators
80     // ##########################################################################
81 
82     /// @{
83 
84     /// copy operator
85     ThreadData< T_DATA >& operator=(const ThreadData< T_DATA >& from) {
86       if (this != &from) data = from.data;
87       return *this;
88     }
89 
90     /// move operator
91     ThreadData< T_DATA >& operator=(ThreadData< T_DATA >&& from) {
92       data = std::move(from.data);
93       return *this;
94     }
95 
96     /// @}
97 
98     /// the data we wish to store without cacheline parallel problem
99     T_DATA data;
100   };
101 
102 } /* namespace gum */
103 
104 #endif /* GUM_THREAD_DATA_H */
105