CHERRY_PICK 20720: fix ts_sort's bug, test=develop (#20726)

test=release/1.6

paddle/fluid/framework/ir/graph_traits.cc

@@ -15,6 +15,7 @@
 #include "paddle/fluid/framework/ir/graph_traits.h"
 
 #include <set>
+#include <utility>
 #include <vector>
 
 namespace paddle {
@@ -79,29 +80,23 @@ NodesTSIterator::NodesTSIterator(const std::vector<Node *> &source) {
     PADDLE_ENFORCE(CheckNodeIndegreeEquals(*node, 0));
   }
 
-  std::unordered_set<Node *> visited;
   std::set<Node *> to_visit{source.begin(), source.end()};
-
-  std::vector<Node *> inlink_visited;
+  std::vector<Node *> inlink_sorted;
   while (!to_visit.empty()) {
     std::vector<Node *> queue(to_visit.begin(), to_visit.end());
     for (auto *p : queue) {
-      inlink_visited.clear();
-
-      std::copy_if(p->inputs.begin(), p->inputs.end(),
-                   std::back_inserter(inlink_visited),
-                   [&](Node *x) -> bool { return visited.count(x) != 0; });
-
-      if (inlink_visited.size() == p->inputs.size()) {
-        sorted_.push_back(p);
-        for (auto *_ : p->outputs) {
-          if (!visited.count(_)) {
-            to_visit.insert(_);
-          }
+      to_visit.erase(p);
+      sorted_.push_back(p);
+      for (auto *out : p->outputs) {
+        inlink_sorted.clear();
+        std::copy_if(out->inputs.begin(), out->inputs.end(),
+                     std::back_inserter(inlink_sorted), [&](Node *x) -> bool {
+                       return std::find(sorted_.begin(), sorted_.end(), x) !=
+                              sorted_.end();
+                     });
+        if (inlink_sorted.size() == out->inputs.size()) {
+          to_visit.insert(out);
         }
-
-        to_visit.erase(p);
-        visited.insert(p);
       }
     }
   }