Enable less_than ngraph operator (#17642)

* Enable less_than ngraph operator

test=develop

* Added compare unit-tests test=develop

* Update: date && removed import test=develop

paddle/fluid/operators/ngraph/ops/elementwise_node.h

@@ -72,3 +72,4 @@ REGISTER_NG_OP(elementwise_sub,
                BuildElementwiseBinaryNode<ngraph::op::Subtract>);
 REGISTER_NG_OP(elementwise_min,
                BuildElementwiseBinaryNode<ngraph::op::Minimum>);
+REGISTER_NG_OP(less_than, BuildElementwiseCompareNode<ngraph::op::Less>);

python/paddle/fluid/tests/unittests/ngraph/test_compare_ngraph_op.py

@@ -0,0 +1,23 @@
+#   Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import unittest
+import sys
+sys.path.append("../")
+import test_compare_op
+
+if __name__ == '__main__':
+    unittest.main()