Merge pull request #24577 from dkurt:dnn_graph_match_stack

Fix graph fusion with commutative ops #24577

### Pull Request Readiness Checklist

resolves https://github.com/opencv/opencv/issues/24568

**Merge with extra**: https://github.com/opencv/opencv_extra/pull/1125

TODO:
- [x]  replace recursive function to sequential

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/dnn/src/graph_simplifier.cpp

@@ -81,26 +81,45 @@ bool Subgraph::match(const Ptr<ImportGraphWrapper>& net, int nodeId,
 {
     matchedNodesIds.clear();
 
-    std::queue<int> nodesToMatch;
-    std::queue<int> targetNodes;
-    std::vector<std::pair<int, int> > matchings;
-    matchings.reserve(nodes.size());
-    nodesToMatch.push(nodeId);
-    targetNodes.push(nodes.size() - 1);
-    while (!nodesToMatch.empty())
-    {
-        int nodeToMatch = nodesToMatch.front();
-        int targetNodeId = targetNodes.front();
-        nodesToMatch.pop();
-        targetNodes.pop();
+    // Collection of all matchings states across branching.
+    // If there is no commutative ops in the subgraph - there would be just a single map.
+    std::vector<std::shared_ptr<std::map<int, int>>> matchCandidates;
+    matchCandidates.push_back(makePtr<std::map<int, int>>());
 
-        if (std::find_if(matchings.begin(), matchings.end(), [&](const std::pair<int, int>& match){ return match.first == targetNodeId; }) !=
-            matchings.end())
+    struct State
+    {
+        int nodeToMatch;
+        int targetNodeId;
+        // Every state refers to current matchings pairs as well as
+        // matchings from parent branches produced by commutative ops.
+        std::vector<std::shared_ptr<std::map<int, int>>> matchings;
+
+        // When we register a matching pair we should register it in every parent branch.
+        // This is actual for branching in case of commutative ops only.
+        void addMatch(std::pair<int, int> match)
+        {
+            for (auto& m : matchings)
+                m->insert(match);
+        }
+    };
+
+    std::queue<State> states;
+    states.push({nodeId, (int)nodes.size() - 1, matchCandidates});
+
+    while (!states.empty())
+    {
+        auto state = states.front();
+        states.pop();
+        int nodeToMatch = state.nodeToMatch;
+        int targetNodeId = state.targetNodeId;
+        auto matchings = state.matchings.back();
+
+        if (matchings->find(targetNodeId) != matchings->end())
             continue;
 
         // Empty placeholder matches with any input type
         if (nodes[targetNodeId].empty()) {
-            matchings.push_back({targetNodeId, nodeToMatch});
+            state.addMatch({targetNodeId, nodeToMatch});
             continue;
         }
 
@@ -112,42 +131,50 @@ bool Subgraph::match(const Ptr<ImportGraphWrapper>& net, int nodeId,
         if (inputNodes.size() != node->getNumInputs())
             continue;
 
-        bool isCommutative = net->isCommutativeOp(node->getType());
+        state.addMatch({targetNodeId, nodeToMatch});
 
-        for (int j = 0; j < inputNodes.size(); ++j)
+        bool isCommutative = net->isCommutativeOp(node->getType());
+        if (isCommutative)
         {
-            // Sometimes, ONNX may have input but it's empty (see Clip layer from reduceL2_subgraph2_2 testcase)
-            if (node->getInputName(j).empty())
-                continue;
-            nodeId = getInputNodeId(net, node, j);
-            const Ptr<ImportNodeWrapper> inpNode = net->getNode(nodeId);
-            if (isCommutative)
+            if (inputNodes.size() != 2)
+                CV_Error(Error::StsNotImplemented, "Commutative op fusion with more than 2 inputs");
+
+            auto newMatchings = makePtr<std::map<int, int>>(*matchings);
+            matchCandidates.push_back(newMatchings);
+            state.matchings.push_back(newMatchings);
+            states.push({getInputNodeId(net, node, 0), inputNodes[0], state.matchings});
+            states.push({getInputNodeId(net, node, 1), inputNodes[1], state.matchings});
+            state.matchings.pop_back();
+
+            newMatchings = makePtr<std::map<int, int>>(*matchings);
+            matchCandidates.push_back(newMatchings);
+            state.matchings.push_back(newMatchings);
+            states.push({getInputNodeId(net, node, 0), inputNodes[1], state.matchings});
+            states.push({getInputNodeId(net, node, 1), inputNodes[0], state.matchings});
+            state.matchings.pop_back();
+        }
+        else
+        {
+            for (int j = 0; j < inputNodes.size(); ++j)
             {
-                for (int i = 0; i < inputNodes.size(); ++i)
-                {
-                    nodesToMatch.push(nodeId);
-                    targetNodes.push(inputNodes[i]);
-                }
-            }
-            else
-            {
-                nodesToMatch.push(nodeId);
-                targetNodes.push(inputNodes[j]);
+                nodeId = getInputNodeId(net, node, j);
+                states.push({nodeId, inputNodes[j], state.matchings});
             }
         }
-        matchings.push_back({targetNodeId, nodeToMatch});
     }
-    if (matchings.size() != nodes.size())
-        return false;
-
-    // Sort matched by pattern nodes order.
-    std::sort(matchings.begin(), matchings.end());
-    matchedNodesIds.resize(matchings.size());
-    for (int i = 0; i < matchings.size(); ++i)
+    for (auto& matchings : matchCandidates)
     {
-        matchedNodesIds[i] = matchings[i].second;
+        if (matchings->size() != nodes.size())
+            continue;
+        matchedNodesIds.resize(matchings->size());
+        for (int i = 0; i < matchings->size(); ++i)
+        {
+            CV_Assert(matchings->find(i) != matchings->end());
+            matchedNodesIds[i] = matchings->at(i);
+        }
+        return true;
     }
-    return true;
+    return false;
 }
 
 void Subgraph::replace(const Ptr<ImportGraphWrapper>& net, const std::vector<int>& matchedNodesIds)

modules/dnn/src/onnx/onnx_graph_simplifier.cpp

@@ -64,6 +64,12 @@ class ONNXGraphWrapper : public ImportGraphWrapper
 public:
     ONNXGraphWrapper(opencv_onnx::GraphProto& _net) : net(_net)
     {
+        // Add a fake initializer with empty name.
+        // Some ONNX models skip their inputs. For example,
+        // Resize which has 4 inputs but 2 of them have empty names.
+        // So we add a fake empty node to which such ops may refer as input.
+        net.add_initializer();
+
         numInputs = net.input_size();
         numInitializers = net.initializer_size();
     }

modules/dnn/src/onnx/onnx_importer.cpp

@@ -3539,7 +3539,7 @@ void ONNXImporter::parseQGemm(LayerParams& layerParams, const opencv_onnx::NodeP
     Mat bias;
     if (constBlobs.find(node_proto.input(6)) != constBlobs.end())
         bias = getBlob(node_proto, 6);
-    else
+    if (bias.empty())
         bias = Mat::zeros(1, outCn, CV_32S);
 
     Mat biasFused(1, outCn, CV_32S);

modules/dnn/test/test_graph_simplifier.cpp

@@ -35,6 +35,7 @@ class Test_Graph_Simplifier : public ::testing::Test {
 
 TEST_F(Test_Graph_Simplifier, GeluSubGraph) {
     test("gelu", "Gelu");
+    test("bias_gelu", std::vector<std::string>{"Gelu", "NaryEltwise"});
 }
 
 TEST_F(Test_Graph_Simplifier, GeluApproximationSubGraph) {