[MLIR] Fix non-determ. order of nodes in MLIR sub-graphs (#3614)

Replace set with vector container in MLIR sub-graphs for
nodes, inputs and outputs. Using a set caused different order of
operations in MLIR code across different executions and this led to
differences in optimizations.

src/contrib/mlir/compiler/pass/mlir_subgraph_extraction.cpp

@@ -48,29 +48,28 @@ using namespace ngraph::pass;
 
 int MLIRSubgraphExtractionPass::MLIRSubgraph::m_curr_graph_id = 0;
 
-template <typename T>
-void MLIRSubgraphExtractionPass::MLIRSubgraph::add_inputs(T& inputs)
+void MLIRSubgraphExtractionPass::MLIRSubgraph::add_inputs(NodeVector& inputs)
 {
     // inputs list are not exclusive, avoid duplication
     for (auto node : inputs)
     {
-        if (m_input_nodes.find(node) == m_input_nodes.end())
+        if (m_input_node_set.insert(node).second)
         {
-            m_input_nodes.insert(node);
+            m_input_node_vector.push_back(node);
         }
     }
 }
 
-template <typename T>
-void MLIRSubgraphExtractionPass::MLIRSubgraph::add_outputs(T& outputs)
+void MLIRSubgraphExtractionPass::MLIRSubgraph::add_outputs(NodeVector& outputs)
 {
-    m_output_nodes.insert(outputs.begin(), outputs.end());
+    m_output_nodes.insert(m_output_nodes.end(), outputs.begin(), outputs.end());
 }
 
 void MLIRSubgraphExtractionPass::MLIRSubgraph::add_node(std::shared_ptr<Node> node)
 {
-    NGRAPH_CHECK(m_nodes.find(node) == m_nodes.end(), "node added to graph before");
-    m_nodes.insert(node);
+    NGRAPH_CHECK(m_pass.m_node_to_graph.find(node) == m_pass.m_node_to_graph.end(),
+                 "node added to graph before");
+    m_nodes.emplace_back(node);
     m_pass.m_node_to_graph[node] = get_id();
 }
 
@@ -89,7 +88,7 @@ void MLIRSubgraphExtractionPass::MLIRSubgraph::merge(MLIRSubgraph& sg2)
     }
 
     // nodes  of sub-graphs are exclusive
-    m_nodes.insert(sg2.get_nodes().begin(), sg2.get_nodes().end());
+    m_nodes.insert(m_nodes.end(), sg2.get_nodes().begin(), sg2.get_nodes().end());
     // merge inputs
     add_inputs(sg2.get_inputs());
 

src/contrib/mlir/compiler/pass/mlir_subgraph_extraction.hpp

@@ -53,17 +53,15 @@ namespace ngraph
                 /// Get sub-graph id
                 int get_id() const { return m_graph_id; }
                 /// Get all nodes in the sub-graph.
-                NodeSet& get_nodes() { return m_nodes; }
+                NodeVector& get_nodes() { return m_nodes; }
                 /// Get input nodes. Predecessors to head nodes.
-                NodeSet& get_inputs() { return m_input_nodes; }
+                NodeVector& get_inputs() { return m_input_node_vector; }
                 /// Get output nodes. Nodes in the sub-graph with edges to external nodes.
-                NodeSet& get_outputs() { return m_output_nodes; }
+                NodeVector& get_outputs() { return m_output_nodes; }
                 /// Add a list of input nodes to the sub-graph.
-                template <typename T>
-                void add_inputs(T& inputs);
+                void add_inputs(NodeVector& inputs);
                 /// Add a list of output nodes to the sub-graph.
-                template <typename T>
-                void add_outputs(T& outputs);
+                void add_outputs(NodeVector& outputs);
                 /// Merges sub-graph (other) into this sub-graph. other will be destroyed.
                 void merge(MLIRSubgraph& other);
                 /// Add one node to the sub-graph.
@@ -73,10 +71,13 @@ namespace ngraph
                 // Unique ID for this sub-graph.
                 int m_graph_id;
                 // Actual nodes of the sub-graph
-                NodeSet m_nodes;
-                // Predecessor to head nodes in the sub-graph.
-                NodeSet m_input_nodes;
-                NodeSet m_output_nodes;
+                NodeVector m_nodes;
+                // Predecessor to head nodes in the sub-graph. Both containers have the same
+                // elements. Set is only used for efficient look-up operations.
+                NodeVector m_input_node_vector;
+                NodeSet m_input_node_set;
+
+                NodeVector m_output_nodes;
                 MLIRSubgraphExtractionPass& m_pass;
                 static int m_curr_graph_id;
             };