make static 'next item' counters thread safe by making them atomic (#186)

src/ngraph/function.cpp

@@ -20,7 +20,7 @@
 using namespace std;
 using namespace ngraph;
 
-size_t Function::m_next_instance_id = 0;
+atomic<size_t> Function::m_next_instance_id(0);
 
 Function::Function(const std::shared_ptr<Node>& result,
                    const std::shared_ptr<ValueType>& result_type,
@@ -31,7 +31,7 @@ Function::Function(const std::shared_ptr<Node>& result,
     , m_name(name)
     , m_result_type(result_type)
     , m_ordered_ops_valid(false)
-    , m_instance_id(m_next_instance_id++)
+    , m_instance_id(m_next_instance_id.fetch_add(1))
 {
     size_t i = 0;
     for (auto parameter : parameters)

src/ngraph/function.hpp

@@ -14,6 +14,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <initializer_list>
 #include <list>
 #include <memory>
@@ -68,7 +69,7 @@ namespace ngraph
         Function(const Function&) = delete;
         Function(const Function&&) = delete;
 
-        static size_t m_next_instance_id;
+        static std::atomic<size_t> m_next_instance_id;
         size_t m_instance_id;
     };
 }

src/ngraph/node.cpp

@@ -17,12 +17,12 @@
 using namespace std;
 using namespace ngraph;
 
-size_t Node::m_next_instance_id = 0;
+atomic<size_t> Node::m_next_instance_id(0);
 
 Node::Node(const std::vector<shared_ptr<Node>>& arguments, shared_ptr<ValueType> value_type)
     : m_arguments(arguments)
     , m_value_type(value_type)
-    , m_instance_id(m_next_instance_id++)
+    , m_instance_id(m_next_instance_id.fetch_add(1))
     , m_is_output(false)
 {
     // Add this node as a user of each argument.

src/ngraph/node.hpp

@@ -14,6 +14,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <set>
 #include <string>
 #include <unordered_set>
@@ -114,7 +115,7 @@ namespace ngraph
         std::multiset<Node*> m_users;
         std::string m_name;
         size_t m_instance_id;
-        static size_t m_next_instance_id;
+        static std::atomic<size_t> m_next_instance_id;
         std::deque<descriptor::Input> m_inputs;
         std::deque<descriptor::Output> m_outputs;
         bool m_is_output;