Tweak to GPUPrimitiveEmitter::lookup (#1814)

src/ngraph/runtime/gpu/gpu_primitive_emitter.cpp

@@ -64,11 +64,12 @@ size_t GPUPrimitiveEmitter::insert(const gpu::memory_primitive& f)
     m_gpu_mem_primitives.push_back(f);
     return m_gpu_mem_primitives.size() - 1;
 }
-size_t GPUPrimitiveEmitter::lookup(std::string hash)
+size_t GPUPrimitiveEmitter::lookup(const std::string& hash)
 {
-    if (m_primitive_map.count(hash) > 0)
+    auto it = m_primitive_map.find(hash);
+    if (it != m_primitive_map.end())
     {
-        return m_primitive_map[hash];
+        return it->second;
     }
     return std::numeric_limits<size_t>::max();
 }

src/ngraph/runtime/gpu/gpu_primitive_emitter.hpp

@@ -44,7 +44,7 @@ namespace ngraph
                 }
                 size_t insert(std::unique_ptr<gpu::primitive>&& f);
                 size_t insert(const gpu::memory_primitive& f);
-                size_t lookup(std::string hash);
+                size_t lookup(const std::string& hash);
                 void cache(const std::string& hash, const size_t& index);
                 GPUAllocator get_memory_allocator() { return m_memory_manager.build_allocator(); }
                 void allocate_primitive_memory() { m_memory_manager.allocate(); }