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fix the thread-safety of the lazy construction of the tree 

* use c++11 memory model to fix the Double-Checked Locking
This commit is contained in:
Sébastien Loriot 2020-04-22 11:10:03 +02:00
parent 6d6b8426ad
commit c5ba7d4621
1 changed files with 81 additions and 61 deletions
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142
AABB_tree/include/CGAL/AABB_tree.h
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@ -209,9 +209,9 @@ namespace CGAL {
set_primitive_data_impl(CGAL::Boolean_tag<internal::Has_nested_type_Shared_data<Primitive>::value>(),std::forward<T>(t)...); set_primitive_data_impl(CGAL::Boolean_tag<internal::Has_nested_type_Shared_data<Primitive>::value>(),std::forward<T>(t)...);
} }
bool build_kd_tree() const; bool build_kd_tree();
template<typename ConstPointIterator> template<typename ConstPointIterator>
bool build_kd_tree(ConstPointIterator first, ConstPointIterator beyond) const; bool build_kd_tree(ConstPointIterator first, ConstPointIterator beyond);
public: public:
/// \name Intersection Tests /// \name Intersection Tests
@ -441,10 +441,6 @@ public:
template<typename ConstPointIterator> template<typename ConstPointIterator>
bool accelerate_distance_queries(ConstPointIterator first, ConstPointIterator beyond) bool accelerate_distance_queries(ConstPointIterator first, ConstPointIterator beyond)
{ {
#ifdef CGAL_HAS_THREADS
//this ensures that this is done once at a time
CGAL_SCOPED_LOCK(kd_tree_mutex);
#endif
clear_search_tree(); clear_search_tree();
m_use_search_tree = false; // not a default kd-tree m_use_search_tree = false; // not a default kd-tree
return build_kd_tree(first,beyond); return build_kd_tree(first,beyond);
@ -492,7 +488,7 @@ public:
delete m_p_search_tree; delete m_p_search_tree;
m_p_search_tree = nullptr; m_p_search_tree = nullptr;
m_search_tree_constructed = false; m_search_tree_constructed = false;
} }
} }
public: public:
@ -531,9 +527,7 @@ public:
Point_and_primitive_id best_hint(const Point& query) const Point_and_primitive_id best_hint(const Point& query) const
{ {
if(m_search_tree_constructed) if(m_search_tree_constructed)
{
return m_p_search_tree->closest_point(query); return m_p_search_tree->closest_point(query);
}
else else
return this->any_reference_point_and_id(); return this->any_reference_point_and_id();
} }
@ -558,19 +552,23 @@ public:
// single root node // single root node
Node* m_p_root_node; Node* m_p_root_node;
#ifdef CGAL_HAS_THREADS #ifdef CGAL_HAS_THREADS
mutable CGAL_MUTEX internal_tree_mutex;//mutex used to protect const calls inducing build() mutable CGAL_MUTEX build_mutex; // mutex used to protect const calls inducing build() and build_kd_tree()
mutable CGAL_MUTEX kd_tree_mutex;//mutex used to protect calls to accelerate_distance_queries
#endif #endif
const Node* root_node() const { const Node* root_node() const {
CGAL_assertion(size() > 1); CGAL_assertion(size() > 1);
#ifdef CGAL_HAS_THREADS
bool m_need_build = m_atomic_need_build.load(std::memory_order_acquire);
#endif
if(m_need_build){ if(m_need_build){
#ifdef CGAL_HAS_THREADS #ifdef CGAL_HAS_THREADS
//this ensures that build() will be called once //this ensures that build() will be called once
CGAL_SCOPED_LOCK(internal_tree_mutex); CGAL_SCOPED_LOCK(build_mutex);
m_need_build = m_atomic_need_build.load(std::memory_order_relaxed);
if(m_need_build) if(m_need_build)
#endif #endif
const_cast< AABB_tree<AABBTraits>* >(this)->build(); const_cast< AABB_tree<AABBTraits>* >(this)->build();
} }
return m_p_root_node; return m_p_root_node;
} }
@ -583,8 +581,12 @@ public:
// search KD-tree // search KD-tree
mutable const Search_tree* m_p_search_tree; mutable const Search_tree* m_p_search_tree;
mutable bool m_search_tree_constructed; mutable bool m_search_tree_constructed;
mutable bool m_use_search_tree; // indicates whether the internal kd-tree should be built bool m_use_search_tree; // indicates whether the internal kd-tree should be built
#ifdef CGAL_HAS_THREADS
std::atomic<bool> m_atomic_need_build;
#else
bool m_need_build; bool m_need_build;
#endif
private: private:
// Disabled copy constructor & assignment operator // Disabled copy constructor & assignment operator
@ -604,7 +606,11 @@ public:
, m_p_search_tree(nullptr) , m_p_search_tree(nullptr)
, m_search_tree_constructed(false) , m_search_tree_constructed(false)
, m_use_search_tree(true) , m_use_search_tree(true)
#ifdef CGAL_HAS_THREADS
, m_atomic_need_build(false)
#else
, m_need_build(false) , m_need_build(false)
#endif
{} {}
template<typename Tr> template<typename Tr>
@ -618,7 +624,11 @@ public:
, m_p_search_tree(nullptr) , m_p_search_tree(nullptr)
, m_search_tree_constructed(false) , m_search_tree_constructed(false)
, m_use_search_tree(true) , m_use_search_tree(true)
#ifdef CGAL_HAS_THREADS
, m_atomic_need_build(false)
#else
, m_need_build(false) , m_need_build(false)
#endif
{ {
// Insert each primitive into tree // Insert each primitive into tree
insert(first, beyond,std::forward<T>(t)...); insert(first, beyond,std::forward<T>(t)...);
@ -636,7 +646,11 @@ public:
m_primitives.push_back(Primitive(first,std::forward<T>(t)...)); m_primitives.push_back(Primitive(first,std::forward<T>(t)...));
++first; ++first;
} }
#ifdef CGAL_HAS_THREADS
m_atomic_need_build.store(true);
#else
m_need_build = true; m_need_build = true;
#endif
} }
// Clears tree and insert a set of primitives // Clears tree and insert a set of primitives
@ -655,56 +669,69 @@ public:
build(); build();
} }
template<typename Tr> template<typename Tr>
template<typename ... T> template<typename ... T>
void AABB_tree<Tr>::build(T&& ... t) void AABB_tree<Tr>::build(T&& ... t)
{ {
set_shared_data(std::forward<T>(t)...); set_shared_data(std::forward<T>(t)...);
build(); build();
} }
template<typename Tr> template<typename Tr>
void AABB_tree<Tr>::insert(const Primitive& p) void AABB_tree<Tr>::insert(const Primitive& p)
{ {
m_primitives.push_back(p); m_primitives.push_back(p);
#ifdef CGAL_HAS_THREADS
m_atomic_need_build.store(true);
#else
m_need_build = true; m_need_build = true;
#endif
} }
// Build the data structure, after calls to insert(..) // Build the data structure, after calls to insert(..)
template<typename Tr> template<typename Tr>
void AABB_tree<Tr>::build() void AABB_tree<Tr>::build()
{ {
clear_nodes(); #ifdef CGAL_HAS_THREADS
if(m_primitives.size() > 1) { if (m_atomic_need_build.load())
#else
if (m_need_build)
#endif
{
clear_nodes();
if(m_primitives.size() > 1) {
// allocates tree nodes // allocates tree nodes
m_p_root_node = new Node[m_primitives.size()-1](); m_p_root_node = new Node[m_primitives.size()-1]();
if(m_p_root_node == nullptr) if(m_p_root_node == nullptr)
{ {
std::cerr << "Unable to allocate memory for AABB tree" << std::endl; std::cerr << "Unable to allocate memory for AABB tree" << std::endl;
CGAL_assertion(m_p_root_node != nullptr); CGAL_assertion(m_p_root_node != nullptr);
m_primitives.clear(); m_primitives.clear();
clear(); clear();
}
// constructs the tree
m_p_root_node->expand(m_primitives.begin(), m_primitives.end(),
m_primitives.size(), m_traits);
} }
#ifdef CGAL_HAS_THREADS
// constructs the tree m_atomic_need_build.store(false, std::memory_order_release); // in case build() is triggered by a call to root_node()
m_p_root_node->expand(m_primitives.begin(), m_primitives.end(), #else
m_primitives.size(), m_traits); m_need_build = false;
#endif
} }
// In case the users has switched on the accelerated distance query // In case the users has switched on the accelerated distance query
// data structure with the default arguments, then it has to be // data structure with the default arguments, then it has to be
// /built/rebuilt. // /built/rebuilt.
if(m_use_search_tree && !empty()){ if(!empty() && m_use_search_tree && !m_search_tree_constructed)
build_kd_tree(); build_kd_tree();
}
m_need_build = false;
} }
// constructs the search KD tree from given points // constructs the search KD tree from given points
// to accelerate the distance queries // to accelerate the distance queries
template<typename Tr> template<typename Tr>
bool AABB_tree<Tr>::build_kd_tree() const bool AABB_tree<Tr>::build_kd_tree()
{ {
// iterate over primitives to get reference points on them // iterate over primitives to get reference points on them
std::vector<Point_and_primitive_id> points; std::vector<Point_and_primitive_id> points;
@ -727,10 +754,10 @@ public:
template<typename Tr> template<typename Tr>
template<typename ConstPointIterator> template<typename ConstPointIterator>
bool AABB_tree<Tr>::build_kd_tree(ConstPointIterator first, bool AABB_tree<Tr>::build_kd_tree(ConstPointIterator first,
ConstPointIterator beyond) const ConstPointIterator beyond)
{ {
m_p_search_tree = new Search_tree(first, beyond); m_p_search_tree = new Search_tree(first, beyond);
m_use_search_tree = true;
if(m_p_search_tree != nullptr) if(m_p_search_tree != nullptr)
{ {
m_search_tree_constructed = true; m_search_tree_constructed = true;
@ -753,31 +780,24 @@ public:
// constructs the search KD tree from internal primitives // constructs the search KD tree from internal primitives
template<typename Tr> template<typename Tr>
bool AABB_tree<Tr>::accelerate_distance_queries() const bool AABB_tree<Tr>::accelerate_distance_queries()
{ {
if(m_primitives.empty()) return true; if(m_primitives.empty()) return true;
#ifdef CGAL_HAS_THREADS
bool m_need_build = m_atomic_need_build.load();;
#endif
if (m_use_search_tree) if (m_use_search_tree)
{ {
if (!m_need_build) return m_search_tree_constructed; if (!m_need_build) return m_search_tree_constructed;
return true; // default return type, no tree built return true; // default return type, no tree built
} }
else
m_use_search_tree = true;
build_kd_tree();
if(!m_need_build) // the tree was already built, build the kd-tree
{
#ifdef CGAL_HAS_THREADS
//this ensures that this function will be done once
CGAL_SCOPED_LOCK(kd_tree_mutex);
#endif
if (!m_need_build)
{
// clears current KD tree
clear_search_tree();
bool res = build_kd_tree();
m_use_search_tree = true;
return res;
};
}
m_use_search_tree = true;
return m_search_tree_constructed; return m_search_tree_constructed;
} }