GetFEM  5.4.2
dal_singleton.h
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4  Copyright (C) 2004-2020 Julien Pommier
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30 ===========================================================================*/
31 
32 /**@file dal_singleton.h
33 @author Julien Pommier <Julien.Pommier@insa-toulouse.fr>
34 @date May 2004.
35 @brief A simple singleton implementation
36 
37 Singleton was made thread safe for OpenMP
38 However, now there is a singleton instance for every
39 thread (singleton is thread local). This replicates
40 the behaviour of singletons in distributed MPI-like
41 environment;
42 */
43 
44 #pragma once
45 
46 #include <vector>
47 #include <memory>
48 
49 #include "getfem_omp.h"
50 
51 
52 namespace dal {
53 
54  using bgeot::size_type;
55 
56  class singleton_instance_base {
57  public:
58  virtual ~singleton_instance_base() {};
59  virtual int level() const = 0;
60  };
61 
62  class singletons_manager {
64  size_type nb_partitions;
65  static singletons_manager& manager();
66 
67  public:
68  static void register_new_singleton(singleton_instance_base *p);
69  static void register_new_singleton(singleton_instance_base *p,
70  size_t ithread);
71  static void on_partitions_change();
72 
73  /**destroy singletons in increasing order*/
74  ~singletons_manager();
75 
76  private:
77  singletons_manager();
78  };
79 
80  template <typename T, int LEV>
81  class singleton_instance : public singleton_instance_base {
82 
83  static getfem::omp_distribute<T*>* initializing_pointer;
84 
85  static getfem::omp_distribute<T*>*& pointer() {
86  static auto p = new getfem::omp_distribute<T*>{};
87  return p;
88  }
89 
90  static T*& instance_pointer() {
91  return pointer()->thrd_cast();
92  }
93 
94  static T*& instance_pointer(size_t ithread) {
95  return (*pointer())(ithread);
96  }
97 
98  public:
99 
100  /**Instance from thread ithread*/
101  inline static T& instance(size_t ithread) {
102  pointer()->on_thread_update();
103  T*& tinstance_ = instance_pointer(ithread);
104  if (!tinstance_) {
105  tinstance_ = new T();
106  singletons_manager::register_new_singleton(
107  new singleton_instance<T,LEV>(), ithread);
108  }
109  return *instance_pointer(ithread);
110  }
111 
112  /** Instance from the current thread*/
113  inline static T& instance() {
114  return instance(this_thread());
115  }
116 
117  inline static size_type num_threads() {
118  return pointer()->num_threads();
119  }
120 
121  inline static size_type this_thread() {
122  return pointer()->this_thread();
123  }
124 
125  int level() const override {
126  return LEV;
127  }
128 
129  ~singleton_instance() {
130  if (!pointer()) return;
131  for(size_t i = 0; i != pointer()->num_threads(); ++i) {
132  auto &p_singleton = (*pointer())(i);
133  if(p_singleton){
134  delete p_singleton;
135  p_singleton = nullptr;
136  }
137  }
138  delete pointer();
139  pointer() = nullptr;
140  if (initializing_pointer) initializing_pointer = nullptr;
141  }
142  };
143 
144  template<typename T, int LEV> getfem::omp_distribute<T*>*
145  singleton_instance<T, LEV>::initializing_pointer = singleton_instance<T, LEV>::pointer();
146 
147  /** singleton class.
148 
149  usage:
150  @code
151  foo &f = singleton<foo>::instance();
152  const foo &f = singleton<foo>::const_instance();
153  @endcode
154  the LEV template arguments allows one to choose the order of destruction
155  of the singletons:
156  lowest LEV will be destroyed first.
157  */
158  template <typename T, int LEV=1> class singleton {
159  public:
160 
161  singleton(const singleton&) = delete;
162  singleton& operator=(const singleton&) = delete;
163 
164  /** Instance from the current thread*/
165  inline static T& instance() {
166  return singleton_instance<T,LEV>::instance();
167  }
168 
169  inline static const T& const_instance() {
170  return instance();
171  }
172 
173  inline static T& instance(size_t ithread) {
174  return singleton_instance<T,LEV>::instance(ithread);
175  }
176 
177  inline static const T& const_instance(size_t ithread){
178  return instance(ithread);
179  }
180 
181  /** number of threads this singleton is distributed on.*/
182  inline static size_type num_threads(){
183  return singleton_instance<T,LEV>::num_threads();
184  }
185 
186  /** this thread number according to the threading policy of the singleton*/
187  inline static size_type this_thread() {
188  return singleton_instance<T, LEV>::this_thread();
189  }
190 
191  protected:
192  singleton() = default;
193  ~singleton() = default;
194  };
195 
196 }/* end of namespace dal */
dal::singleton::instance
static T & instance()
Instance from the current thread.
Definition: dal_singleton.h:165
dal::singleton::this_thread
static size_type this_thread()
this thread number according to the threading policy of the singleton
Definition: dal_singleton.h:187
bgeot::size_type
size_t size_type
used as the common size type in the library
Definition: bgeot_poly.h:49
dal
Dynamic Array Library.
Definition: dal_backtrace.cc:29
dal::singleton::num_threads
static size_type num_threads()
number of threads this singleton is distributed on.
Definition: dal_singleton.h:182
getfem_omp.h
Tools for multithreaded, OpenMP and Boost based parallelization.
getfem::omp_distribute
Use this template class for any object you want to distribute to open_MP threads.
Definition: getfem_omp.h:325
dal::singleton
singleton class.
Definition: dal_singleton.h:158