fix graph pattern detector (#14186)

paddle/fluid/framework/ir/graph_pattern_detector.cc

@@ -259,6 +259,15 @@ GraphPatternDetector::DetectPatterns() {
   return result;
 }
 
+bool GraphItemCMP(const std::pair<PDNode *, Node *> &a,
+                  const std::pair<PDNode *, Node *> &b) {
+  if (a.first != b.first) {
+    return a.first < b.first;
+  } else {
+    return a.second < b.second;
+  }
+}
+
 // TODO(Superjomn) enhance the function as it marks unique unique as duplicates
 // see https://github.com/PaddlePaddle/Paddle/issues/13550
 void GraphPatternDetector::UniquePatterns(
@@ -267,12 +276,16 @@ void GraphPatternDetector::UniquePatterns(
   std::vector<GraphPatternDetector::subgraph_t> result;
 
   std::unordered_set<size_t> set;
+  std::hash<std::string> hasher;
   for (auto &g : *subgraphs) {
-    size_t key = 0;
-    for (auto &item : g) {
-      key ^= std::hash<void *>{}(item.first);
-      key ^= std::hash<void *>{}(item.second);
+    // Sort the items in the sub-graph, and transform to a string key.
+    std::vector<std::pair<PDNode *, Node *>> sorted_keys(g.begin(), g.end());
+    std::sort(sorted_keys.begin(), sorted_keys.end(), GraphItemCMP);
+    std::stringstream ss;
+    for (auto &item : sorted_keys) {
+      ss << item.first << ":" << item.second;
     }
+    auto key = hasher(ss.str());
     if (!set.count(key)) {
       result.emplace_back(g);
       set.insert(key);