Merge pull request #3182 from NervanaSystems/pruthvi/fix_segfautl_mem_allocator

Fix Onnx CI seg fault 

src/ngraph/runtime/allocator.cpp

@@ -49,7 +49,8 @@ public:
     }
 };
 
-std::unique_ptr<ngraph::runtime::Allocator> ngraph::runtime::create_default_allocator()
+ngraph::runtime::Allocator* ngraph::runtime::get_default_allocator()
 {
-    return std::unique_ptr<DefaultAllocator>(new DefaultAllocator());
+    static std::unique_ptr<DefaultAllocator> allocator(new DefaultAllocator());
+    return allocator.get();
 }

src/ngraph/runtime/allocator.hpp

@@ -30,7 +30,7 @@ namespace ngraph
         class DefaultAllocator;
         /// \brief Create a default allocator that calls into system
         ///        allocation libraries
-        std::unique_ptr<Allocator> create_default_allocator();
+        ngraph::runtime::Allocator* get_default_allocator();
     }
 }
 

src/ngraph/runtime/cpu/cpu_backend.cpp

@@ -185,7 +185,7 @@ runtime::Allocator* runtime::cpu::CPU_Backend::get_host_memory_allocator()
 {
     if (!m_allocator)
     {
-        m_allocator = create_default_allocator();
+        return runtime::get_default_allocator();
     }
     return m_allocator.get();
 }