Langjian/allreduce provenance tag (#3120)

* Print provenance_tag name for allreduce op

* Fix a bug

* remove friendly_name print out

* Fix

* More debug

* More bugs

* Bug

* More meaningful outputs

* Better output

* c_str()

* Print friendly_name or provenance_tags

* Print provenance_tags when available

* Add comments

* style

src/ngraph/runtime/cpu/builder/allreduce.cpp

@@ -48,7 +48,12 @@ namespace ngraph
                     call_seq,
                     external_function_name.c_str(),
                     node->get_name().c_str(),
-                    node->get_friendly_name().c_str(),
+                    node->get_provenance_tags().size() == 1
+                        ?
+                        // if provenance_tags is set in nGraph once and only once, it will print the tag name
+                        // otherwise, it will print the get_friendly_name
+                        (*(node->get_provenance_tags()).begin()).c_str()
+                        : node->get_friendly_name().c_str(),
                     count);
 
                 auto functor =