Implement Einsum reference in nGraph interpreter

Signed-off-by: Roman Kazantsev <[email protected]>

ngraph/core/reference/include/ngraph/runtime/reference/einsum.hpp

@@ -0,0 +1,24 @@
+// Copyright (C) 2018-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#pragma once
+
+#include <algorithm>
+
+#include <ngraph/opsets/opset7.hpp>
+
+namespace ngraph
+{
+    namespace runtime
+    {
+        namespace reference
+        {
+            void einsum(const HostTensorVector& outputs, const HostTensorVector& inputs,
+                        const std::string &equation,
+                        const element::Type& input_type);
+        } // namespace reference
+
+    } // namespace runtime
+
+} // namespace ngraph

ngraph/core/reference/include/ngraph/runtime/reference/matmul.hpp

@@ -56,7 +56,7 @@ namespace ngraph
                     }
                 }
 
-                std::vector<size_t> get_transpose_order(const Shape& input_shape)
+                static std::vector<size_t> get_transpose_order(const Shape& input_shape)
                 {
                     size_t rank = input_shape.size();
                     NGRAPH_CHECK(rank > 1, "Invalid input for transpose");