Use node IDs for comparison when sorting in pattern match. (#3105)

* Use node IDs for comparison when sorting in pattern match.

* Make args const.

src/ngraph/pattern/matcher.cpp

@@ -298,9 +298,14 @@ namespace ngraph
 
             if (graph_node->is_commutative())
             {
-                std::sort(
-                    begin(pattern_args),
-                    end(pattern_args)); // TODO: [nikolayk] we don't really have to use lexicographically-based perms, heap's algo should be faster
+                // TODO: [nikolayk] we don't really have to use lexicographically-based perms, heap's algo should be faster
+                std::sort(begin(pattern_args),
+                          end(pattern_args),
+                          [](const std::shared_ptr<ngraph::Node>& n1,
+                             const std::shared_ptr<ngraph::Node>& n2) {
+                              return n1->get_instance_id() < n2->get_instance_id();
+
+                          });
                 do
                 {
                     NGRAPH_DEBUG << pad(2 * m_depth) << "Running a permutation for graph_node "
@@ -311,7 +316,13 @@ namespace ngraph
                         pattern_map.insert(begin(copy), end(copy));
                         return true;
                     }
-                } while (std::next_permutation(begin(pattern_args), end(pattern_args)));
+                } while (std::next_permutation(begin(pattern_args),
+                                               end(pattern_args),
+                                               [](const std::shared_ptr<ngraph::Node>& n1,
+                                                  const std::shared_ptr<ngraph::Node>& n2) {
+                                                   return n1->get_instance_id() <
+                                                          n2->get_instance_id();
+                                               }));
             }
             else
             {

test/pattern.cpp

@@ -514,6 +514,33 @@ TEST(pattern, previous_matches)
     }
 }
 
+TEST(pattern, test_sort)
+{
+    using ngraph::pattern::Matcher;
+    Shape shape{};
+
+    auto a = make_shared<op::Parameter>(element::i32, shape);
+    auto b = make_shared<op::Parameter>(element::i32, shape);
+    auto abs1 = make_shared<op::Abs>(a);
+    auto abs2 = make_shared<op::Abs>(b);
+    auto add = abs1 + abs2;
+
+    auto pa = make_shared<op::Parameter>(element::i32, shape);
+    auto pb = make_shared<op::Parameter>(element::i32, shape);
+    auto pabs1 = make_shared<op::Abs>(pa);
+    auto pabs1_label = std::make_shared<pattern::op::Label>(pabs1);
+    auto pabs2 = make_shared<op::Abs>(b);
+    auto padd = pabs1_label + pabs2;
+
+    {
+        Matcher n1(padd);
+        ASSERT_TRUE(n1.match(add));
+        auto r1 = n1.get_pattern_map()[pabs1_label];
+        ASSERT_TRUE(n1.match(add));
+        ASSERT_EQ(r1, n1.get_pattern_map()[pabs1_label]);
+    }
+}
+
 TEST(pattern, recurrent_pattern)
 {
     using ngraph::pattern::RecurrentMatcher;