masahi commented on code in PR #14417:
URL: https://github.com/apache/tvm/pull/14417#discussion_r1152471948
##########
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:
ok :) I'll share my thought in the meantime.
Looking at an example in
https://github.com/apache/tvm/blob/unity/tests/python/relax/test_dataflow_pattern.py#L540-L545,
I cannot imagine how one would use `start_hint` in practice. Here, you wrote
the input mod by hand, so you know `dfb.bindings[0].var` is associated to the
"left" branch of the CBRx2. But in general, we don't have such information,
especially in e2e scenarios for real world models.
Even if there was a good use case for it, I claim that it doesn't justify
making API and the implementation more complicated (two additional params +
`try_match` loop on parants). If one has such advanced knowledge of model
structure and variables, they may as well have a different way to match &
extract such subgraph.
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