[GitHub] [tvm] ganler commented on a diff in pull request #14417: [Unity] Remove non-deterministic behavior from graph pattern matching

["ganler (via GitHub)" <gi...@apache.org>]

ganler commented on code in PR #14417:
URL: https://github.com/apache/tvm/pull/14417#discussion_r1152431567


##########
src/relax/ir/dataflow_matcher.cc:
##########
@@ -541,15 +541,21 @@ struct RNode {
  * \brief This method try to match a real node and a pattern node along with its neighbors.
  */
 static bool try_match(PNode* p, RNode* r, DFPatternMatcher* m,
-                      const std::map<const VarNode*, std::set<const VarNode*>>& def2use,
+                      const std::map<const VarNode*, std::vector<const VarNode*>>& def2use,
                       const std::map<const VarNode*, std::vector<const VarNode*>>& use2def) {
-  if (nullptr != p->matched && p->matched == r->ptr) return true;  // matched before.
+  if (p->matched != nullptr && p->matched == r->ptr) return true;  // matched before.
   if (!m->Match(GetRef<DFPattern>(p->ptr), GetRef<Var>(r->ptr))) return false;
 
   std::stack<std::pair<PNode*, RNode*>> undo_stack{};
 
   const auto commit = [&undo_stack](PNode* p, RNode* r) {
     // match with each other.
+    // TODO(ganler, masahi): Why commit on the same p-r pair happens more than once?

Review Comment:
   I guess in either way the eventual results are the same. But yeah doing a pre-check could be faster (avoid the overhead of `undo_stack.emplace(p, r)`).



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