add a new graph operation in autoparallel

mindspore/ccsrc/frontend/parallel/auto_parallel/costmodel.h

@@ -79,6 +79,8 @@ class StrategyWithCost {
  public:
   StrategyWithCost(StrategyPtr strategy, std::vector<TensorInfo> inputs_, std::vector<TensorInfo> outputs_)
       : strategy_ptr(std::move(strategy)), inputs_ptr(std::move(inputs_)), outputs_ptr(std::move(outputs_)) {}
+  StrategyWithCost(StrategyPtr strategy, CostPtrList c_list)
+      : strategy_ptr(std::move(strategy)), cost_list(std::move(c_list)) {}
 
   StrategyWithCost(const StrategyWithCost &swc) = delete;
   StrategyWithCost(StrategyWithCost &&swc)
@@ -99,6 +101,7 @@ enum DecisionType {
   EDGE_ELIMINATION,
   MERGE_ELIMINATION,
   CONTRACT_ELIMINATION,
+  SOURCE_ELIMINATION,
   TRIANGLE_ELIMINATION,
   STAR_ELIMINATION,
   FINAL_TYPE,
@@ -199,6 +202,38 @@ struct ContractEliminationDecision : public Decision {
   MS_DECLARE_PARENT(ContractEliminationDecision, Decision);
 };
 
+/* 'SourceEliminationDecision' is for the source Elimination in DP algorithm:
+ *                    1                             1,5
+ *                   /  \                          // \\
+ *                  /    \                        //   \\
+ *                 /      \                      //     \\
+ *                /        \                    //       \\
+ *               2 <-  5 -> 3    ==>           2          3
+ *                \        /                    \        /
+ *                  \    /                        \    /
+ *                    \ /                           \ /
+ *                     4                             4
+ *
+ *  In the original graph, '1' has two alive outgoing edges and no incoming edges. '5' has two alive outgoing edges and
+ *  no incoming edges. '4' has two alive incoming edges and no outgoing edges. Source Elimination will merge '5' into
+ * '1' new edges are generated to replace the old ones incident to '1' and '5'.
+ *
+ */
+struct SourceEliminationDecision : public Decision {
+  SourceEliminationDecision(StrategyPtr op1_stra, CostPtr op1_c, StrategyPtr op2_stra, CostPtr op2_c)
+      : op1_strategy_(std::move(op1_stra)),
+        op1_cost_(std::move(op1_c)),
+        op2_strategy_(std::move(op2_stra)),
+        op2_cost_(std::move(op2_c)) {
+    type_ = DecisionType::SOURCE_ELIMINATION;
+  }
+  StrategyPtr op1_strategy_;
+  CostPtr op1_cost_;
+  StrategyPtr op2_strategy_;
+  CostPtr op2_cost_;
+  MS_DECLARE_PARENT(SourceEliminationDecision, Decision);
+};
+
 /* 'TriangleEliminationDecision' is for the Triangle Elimination in DP algorithm:
  *
  *       u
@@ -296,6 +331,7 @@ using OpEliminationDecisionPtr = std::shared_ptr<OpEliminationDecision>;
 using EdgeEliminationDecisionPtr = std::shared_ptr<EdgeEliminationDecision>;
 using MergeEliminationDecisionPtr = std::shared_ptr<MergeEliminationDecision>;
 using ContractEliminationDecisionPtr = std::shared_ptr<ContractEliminationDecision>;
+using SourceEliminationDecisionPtr = std::shared_ptr<SourceEliminationDecision>;
 using TriangleEliminationDecisionPtr = std::shared_ptr<TriangleEliminationDecision>;
 using StarEliminationDecisionPtr = std::shared_ptr<StarEliminationDecision>;
 using FinalDecisionPtr = std::shared_ptr<FinalDecision>;

mindspore/ccsrc/frontend/parallel/auto_parallel/dp_algo_costmodel.cc

@@ -42,66 +42,76 @@ Status GetStrategy(const CostGraphPtr &graph) {
       auto elimi = std::make_shared<OpElimination>(n_edge, l_edge, node, r_edge);
       eliminations.emplace_back(std::move(elimi));
     }
-    auto edges = graph->CheckEdgeElimination();
-    if ((!flag) && (!edges.empty())) {
-      // Applying the Edge Elimination
-      flag = true;
-      auto n_edge = graph->EliminationEdges(edges);
-      auto elimi = std::make_shared<EdgeElimination>(n_edge, edges);
-      eliminations.emplace_back(std::move(elimi));
+    if (!flag) {
+      auto edges = graph->CheckEdgeElimination();
+      if (!edges.empty()) {
+        // Applying the Edge Elimination
+        flag = true;
+        auto n_edge = graph->EliminationEdges(edges);
+        auto elimi = std::make_shared<EdgeElimination>(n_edge, edges);
+        eliminations.emplace_back(std::move(elimi));
+      }
     }
-    auto merge_node = graph->CheckMergeElimination();
-    if ((!flag) && (merge_node != nullptr)) {
-      // Applying the Merge Elimination
-      flag = true;
-      auto succ_edge = merge_node->GetAliveSuccEdges()[0];
-      auto target_node = graph->EliminationMerge(merge_node);
-      auto elimi = std::make_shared<MergeElimination>(merge_node, succ_edge, target_node);
-      eliminations.emplace_back(std::move(elimi));
+    if (!flag) {
+      auto merge_node = graph->CheckMergeElimination();
+      if (merge_node != nullptr) {
+        // Applying the Merge Elimination
+        flag = true;
+        auto succ_edge = merge_node->GetAliveSuccEdges()[0];
+        auto target_node = graph->EliminationMerge(merge_node);
+        auto elimi = std::make_shared<MergeElimination>(merge_node, succ_edge, target_node);
+        eliminations.emplace_back(std::move(elimi));
+      }
     }
-    auto contracted_node = graph->CheckContractElimination();
-    if ((!flag) && (contracted_node != nullptr)) {
-      // Applying the Contract Elimination
-      flag = true;
-      auto prev_edge = contracted_node->GetAlivePrevEdges()[0];
-      auto target_node = graph->EliminationContract(contracted_node);
-      auto elimi = std::make_shared<ContractElimination>(target_node, prev_edge, contracted_node);
-      eliminations.emplace_back(std::move(elimi));
+    if (!flag) {
+      auto contracted_node = graph->CheckContractElimination();
+      if ((contracted_node != nullptr)) {
+        // Applying the Contract Elimination
+        flag = true;
+        auto prev_edge = contracted_node->GetAlivePrevEdges()[0];
+        auto target_node = graph->EliminationContract(contracted_node);
+        auto elimi = std::make_shared<ContractElimination>(target_node, prev_edge, contracted_node);
+        eliminations.emplace_back(std::move(elimi));
+      }
     }
-    auto triangle_pair = graph->CheckTriangleElimination();
-    if ((!flag) && (triangle_pair.first != nullptr)) {
-      // Applying the Triangle Elimination
-      flag = true;
-      auto eliminated_node = triangle_pair.first;
-      auto l_r_edge = triangle_pair.second;
+    if (!flag) {
+      auto triangle_pair = graph->CheckTriangleElimination();
+      if (triangle_pair.first != nullptr) {
+        // Applying the Triangle Elimination
+        flag = true;
+        auto eliminated_node = triangle_pair.first;
+        auto l_r_edge = triangle_pair.second;
 
-      auto left_node = l_r_edge->prev_operator();
-      auto left_edge = eliminated_node->GetAliveSuccEdges()[0];
-      auto right_edge = eliminated_node->GetAliveSuccEdges()[1];
-      MS_EXCEPTION_IF_NULL(left_edge);
-      if (left_edge->next_operator() != left_node) {
-        auto tmp = left_edge;
-        left_edge = right_edge;
-        right_edge = tmp;
+        auto left_node = l_r_edge->prev_operator();
+        auto left_edge = eliminated_node->GetAliveSuccEdges()[0];
+        auto right_edge = eliminated_node->GetAliveSuccEdges()[1];
+        MS_EXCEPTION_IF_NULL(left_edge);
+        if (left_edge->next_operator() != left_node) {
+          auto tmp = left_edge;
+          left_edge = right_edge;
+          right_edge = tmp;
+        }
+        auto left_node_cpy = graph->EliminationTriangle(eliminated_node, l_r_edge);
+        auto right_node = l_r_edge->next_operator();
+        auto elimi =
+          std::make_shared<TriangleElimination>(eliminated_node, left_edge, left_node_cpy, right_edge, right_node);
+        eliminations.emplace_back(std::move(elimi));
       }
-      auto left_node_cpy = graph->EliminationTriangle(eliminated_node, l_r_edge);
-      auto right_node = l_r_edge->next_operator();
-      auto elimi =
-        std::make_shared<TriangleElimination>(eliminated_node, left_edge, left_node_cpy, right_edge, right_node);
-      eliminations.emplace_back(std::move(elimi));
     }
-    auto star_center = graph->CheckStarElimination();
-    if ((!flag) && (star_center != nullptr)) {
-      // Applying the Star Elimination
-      flag = true;
-      auto succ_edges = graph->EliminationStar(star_center);
-      std::vector<OperatorInfoPtr> succ_nodes;
-      for (size_t i = 0; i < succ_edges.size(); ++i) {
-        MS_EXCEPTION_IF_NULL(succ_edges[i]);
-        succ_nodes.push_back(succ_edges[i]->next_operator());
+    if (!flag) {
+      auto star_center = graph->CheckStarElimination();
+      if (star_center != nullptr) {
+        // Applying the Star Elimination
+        flag = true;
+        auto succ_edges = graph->EliminationStar(star_center);
+        std::vector<OperatorInfoPtr> succ_nodes;
+        for (size_t i = 0; i < succ_edges.size(); ++i) {
+          MS_EXCEPTION_IF_NULL(succ_edges[i]);
+          succ_nodes.push_back(succ_edges[i]->next_operator());
+        }
+        auto elimi = std::make_shared<StarElimination>(star_center, succ_edges, succ_nodes);
+        eliminations.emplace_back(std::move(elimi));
       }
-      auto elimi = std::make_shared<StarElimination>(star_center, succ_edges, succ_nodes);
-      eliminations.emplace_back(std::move(elimi));
     }
   }
 

mindspore/ccsrc/frontend/parallel/auto_parallel/dp_algo_costmodel.h

@@ -42,7 +42,7 @@ namespace parallel {
 //       the operators' strategies can be all determined.
 
 struct Elimination : public Base {
-  enum EliminationType { OPERA, EDGE, MERGE, CONTRACT, TRIANGLE, STAR };
+  enum EliminationType { OPERA, EDGE, MERGE, CONTRACT, SOURCE, TRIANGLE, STAR };
   Elimination(EdgePtr n_edge, EliminationType ty) : new_edge_(std::move(n_edge)), type_(ty) {}
 
   EdgePtr new_edge_;
@@ -100,6 +100,26 @@ struct ContractElimination : public Elimination {
   MS_DECLARE_PARENT(ContractElimination, Elimination);
 };
 
+// Source Elimination
+struct SourceElimination : public Elimination {
+  SourceElimination(OperatorInfoPtr p_source, std::vector<EdgePtr> p_succ_edges, std::vector<EdgePtr> p_new_succ_edges,
+                    OperatorInfoPtr s_source, std::vector<EdgePtr> s_succ_edges, std::vector<EdgePtr> s_new_succ_edges)
+      : Elimination(nullptr, Elimination::EliminationType::SOURCE),
+        primary_source_(std::move(p_source)),
+        primary_succ_edges_(std::move(p_succ_edges)),
+        primary_new_succ_edges_(std::move(p_new_succ_edges)),
+        secondary_source_(std::move(s_source)),
+        secondary_succ_edges_(std::move(s_succ_edges)),
+        secondary_new_succ_edges_(std::move(s_new_succ_edges)) {}
+  OperatorInfoPtr primary_source_;
+  std::vector<EdgePtr> primary_succ_edges_;
+  std::vector<EdgePtr> primary_new_succ_edges_;
+  OperatorInfoPtr secondary_source_;
+  std::vector<EdgePtr> secondary_succ_edges_;
+  std::vector<EdgePtr> secondary_new_succ_edges_;
+  MS_DECLARE_PARENT(SourceElimination, Elimination);
+};
+
 // Triangle Elimination
 struct TriangleElimination : public Elimination {
   TriangleElimination(OperatorInfoPtr elim_node, EdgePtr l_edge, OperatorInfoPtr l_node, EdgePtr r_edge,
@@ -138,6 +158,7 @@ using OpEliminationPtr = std::shared_ptr<OpElimination>;
 using EdgeEliminationPtr = std::shared_ptr<EdgeElimination>;
 using MergeEliminationPtr = std::shared_ptr<MergeElimination>;
 using ContractEliminationPtr = std::shared_ptr<ContractElimination>;
+using SourceEliminationPtr = std::shared_ptr<SourceElimination>;
 using TriangleEliminationPtr = std::shared_ptr<TriangleElimination>;
 using StarEliminationPtr = std::shared_ptr<StarElimination>;
 

mindspore/ccsrc/frontend/parallel/auto_parallel/edge_costmodel.cc

@@ -320,5 +320,17 @@ Status Edge::CalculateMemoryCostForInference() {
   }
   return SUCCESS;
 }
+
+void Edge::SetCostMapAndInputOutput(std::map<CostPtrKey, CostPtrList> &cost_map) {
+  cost_map_ = cost_map;
+  pre_op_output_.clear();
+  next_op_input_.clear();
+
+  for (auto &key_value : cost_map_) {
+    auto &key_pair = key_value.first;
+    pre_op_output_.emplace_back(std::pair<StrategyPtr, std::vector<TensorInfo>>(key_pair.first, {}));
+    next_op_input_.emplace_back(std::pair<StrategyPtr, std::vector<TensorInfo>>(key_pair.second, {}));
+  }
+}
 }  // namespace parallel
 }  // namespace mindspore

mindspore/ccsrc/frontend/parallel/auto_parallel/edge_costmodel.h

@@ -80,6 +80,8 @@ class Edge {
   std::string edge_name() const { return edge_name_; }
   // Init cost_map_: for each output layout and input layout, calculate the cost
   Status InitEdgeCost();
+  std::map<CostPtrKey, CostPtrList> GetCostMap() { return cost_map_; }
+  void SetCostMapAndInputOutput(std::map<CostPtrKey, CostPtrList> &);
   // For two operators u--->v, given the output tensor layout of u,
   // and the input tensor layout of v, return the redistribution cost,
   // and the op_list to carry out the redistribution.

mindspore/ccsrc/frontend/parallel/auto_parallel/graph_costmodel.cc

@@ -794,6 +794,191 @@ OperatorInfoPtr CostGraph::CheckContractElimination() const {
   return nullptr;
 }
 
+std::pair<OperatorInfoPtr, OperatorInfoPtr> CostGraph::CheckSourceElimination() const {
+  size_t source_count = 0;
+  std::vector<OperatorInfoPtr> op_vector(2, nullptr);
+  for (auto &op : ops_) {
+    MS_EXCEPTION_IF_NULL(op);
+    bool bool_test = op->is_alive() && op->GetAlivePrevEdges().empty() && op->GetAliveSuccEdges().size() > 0;
+    if (bool_test) {
+      op_vector[source_count++] = op;
+      if (source_count == 2) {
+        return std::make_pair(op_vector[0], op_vector[1]);
+      }
+    }
+  }
+  return std::make_pair(nullptr, nullptr);
+}
+
+void CostGraph::CreateSourceEliminationSubCostList(StrategyPtr op1_old_stra, const CostPtrList &op1_old_clist,
+                                                   StrategyPtr op2_old_stra, const CostPtrList &op2_old_clist,
+                                                   CostPtrList *op1_new_clist) {
+  for (auto &op1_cost : op1_old_clist) {
+    for (auto &op2_cost : op2_old_clist) {
+      double computation = op1_cost->computation_cost_ + op2_cost->computation_cost_;
+      double memory = op1_cost->memory_with_reuse_ + op2_cost->memory_with_reuse_;
+      double communication = op1_cost->communication_cost_ + op2_cost->communication_cost_;
+      double communication_forward = op1_cost->communication_forward_ + op2_cost->communication_forward_;
+      double communication_without_para =
+        op1_cost->communication_without_parameter_ + op2_cost->communication_without_parameter_;
+      auto decision = std::make_shared<SourceEliminationDecision>(op1_old_stra, op1_cost, op2_old_stra, op2_cost);
+      auto new_cost = std::make_shared<Cost>(computation, communication, decision);
+      MS_EXCEPTION_IF_NULL(new_cost);
+      new_cost->communication_without_parameter_ = communication_without_para;
+      new_cost->communication_with_partial_para_ =
+        communication_without_para + COST_MODEL_GAMMA * (communication - communication_without_para);
+      new_cost->memory_with_reuse_ = memory;
+      new_cost->communication_forward_ = communication_forward;
+      MS_EXCEPTION_IF_NULL(op1_new_clist);
+      op1_new_clist->emplace_back(std::move(new_cost));
+    }
+  }
+}
+
+std::pair<std::vector<std::shared_ptr<Edge>>, std::vector<std::shared_ptr<Edge>>> CostGraph::EliminationSources(
+  OperatorInfoPtr op1, OperatorInfoPtr op2) {
+  MS_EXCEPTION_IF_NULL(op1);
+  MS_EXCEPTION_IF_NULL(op2);
+  MS_LOG(INFO) << "Now source eliminating node: " << op2->name() << " to node: " << op1->name();
+
+  auto op1_old_succ_edges = op1->GetAliveSuccEdges();
+  std::vector<std::map<StrategyPtr, std::vector<std::pair<StrategyPtr, CostPtrList>>>> op1_edges_reorganised_cost(
+    op1_old_succ_edges.size());
+  std::vector<std::map<CostPtrKey, CostPtrList>> op1_new_edges_cost(op1_old_succ_edges.size());
+  std::vector<std::shared_ptr<Edge>> op1_new_succ_edges(op1_old_succ_edges.size());
+
+  auto op2_old_succ_edges = op2->GetAliveSuccEdges();
+  std::vector<std::map<StrategyPtr, std::vector<std::pair<StrategyPtr, CostPtrList>>>> op2_edges_reorganised_cost(
+    op2_old_succ_edges.size());
+  std::vector<std::map<CostPtrKey, CostPtrList>> op2_new_edges_cost(op2_old_succ_edges.size());
+  std::vector<std::shared_ptr<Edge>> op2_new_succ_edges(op2_old_succ_edges.size());
+
+  // Construct cost_map for the data_structure of 'op1_edges_reorganised_cost' and 'op2_edges_reorganised_cost'
+  for (size_t i = 0; i < op1_old_succ_edges.size(); ++i) {
+    const auto &op1_cost_map = op1_old_succ_edges[i]->GetCostMap();
+    std::map<StrategyPtr, std::vector<std::pair<StrategyPtr, CostPtrList>>> from_tocost;
+    for (const auto &key_value : op1_cost_map) {
+      const auto &from_to_strategies = key_value.first;
+      const auto &costlist = key_value.second;
+      from_tocost[from_to_strategies.first].emplace_back(std::make_pair(from_to_strategies.second, costlist));
+    }
+    op1_edges_reorganised_cost[i] = from_tocost;
+  }
+
+  for (size_t i = 0; i < op2_old_succ_edges.size(); ++i) {
+    const auto &op2_cost_map = op2_old_succ_edges[i]->GetCostMap();
+    std::map<StrategyPtr, std::vector<std::pair<StrategyPtr, CostPtrList>>> from_tocost;
+    for (const auto &key_value : op2_cost_map) {
+      const auto &from_to_strategies = key_value.first;
+      const auto &costlist = key_value.second;
+      from_tocost[from_to_strategies.first].emplace_back(std::make_pair(from_to_strategies.second, costlist));
+    }
+    op2_edges_reorganised_cost[i] = from_tocost;
+  }
+
+  // Merge op2 into op1
+  const auto &op1_old_stra_cost = op1->GetStrategyCost();
+  const auto &op2_old_stra_cost = op2->GetStrategyCost();
+  std::vector<std::shared_ptr<StrategyWithCost>> op1_new_stra_cost;
+
+  for (auto &op1_stra_cost : op1_old_stra_cost) {
+    auto op1_old_stra = op1_stra_cost->strategy_ptr;
+    auto op1_old_costlist = op1_stra_cost->cost_list;
+
+    for (auto &op2_stra_cost : op2_old_stra_cost) {
+      auto op2_stra = op2_stra_cost->strategy_ptr;
+      auto op2_costlist = op2_stra_cost->cost_list;
+
+      StrategyPtr op1_new_stra = std::make_shared<Strategy>(*op1_old_stra);
+      op1_new_stra->CoverStrategy(op2_stra);
+      CostPtrList op1_new_costlist;
+      // Calculate new cost for 'op1_new_costlist'
+      CreateSourceEliminationSubCostList(op1_old_stra, op1_old_costlist, op2_stra, op2_costlist, &op1_new_costlist);
+      std::shared_ptr<StrategyWithCost> swc = std::make_shared<StrategyWithCost>(op1_new_stra, op1_new_costlist);
+      op1_new_stra_cost.emplace_back(swc);
+
+      // Set cost for new successive edges of op1 and op2
+      for (size_t i = 0; i < op1_old_succ_edges.size(); ++i) {
+        auto &from_tocost = op1_edges_reorganised_cost[i];
+        auto &to_cost = from_tocost[op1_old_stra];
+        auto &new_cost_map = op1_new_edges_cost[i];
+        for (auto &stra_costlit : to_cost) {
+          auto &to_strategy = stra_costlit.first;
+          auto &edge_costlist = stra_costlit.second;
+          CostPtrKey new_key = {op1_new_stra, to_strategy};
+          new_cost_map[new_key] = edge_costlist;
+        }
+      }
+      for (size_t i = 0; i < op2_old_succ_edges.size(); ++i) {
+        auto &from_tocost = op2_edges_reorganised_cost[i];
+        auto &to_cost = from_tocost[op2_stra];
+        auto &new_cost_map = op2_new_edges_cost[i];
+        for (auto &stra_costlist : to_cost) {
+          auto &to_strategy = stra_costlist.first;
+          auto &edge_costlist = stra_costlist.second;
+          CostPtrKey new_key = {op1_new_stra, to_strategy};
+          new_cost_map[new_key] = edge_costlist;
+        }
+      }
+    }
+  }
+  op1->SetStrategyCost(op1_new_stra_cost);
+  op2->SetNotAlive();
+
+  // Update the edges incident to op1, and edges incident to op2
+  for (size_t i = 0; i < op1_old_succ_edges.size(); ++i) {
+    auto &new_cost_map = op1_new_edges_cost[i];
+    auto &ith_edge = op1_old_succ_edges[i];
+
+    std::string new_edge_name = op1->name() + OPERATOR_TO_OPERATOR_CONNECTOR + ith_edge->next_operator()->name();
+    std::shared_ptr<Edge> new_edge;
+    if (ith_edge->is_combined()) {
+      std::vector<size_t> output_indexs, input_indexs;
+      output_indexs = ith_edge->prev_op_output_indexs();
+      input_indexs = ith_edge->next_op_input_indexs();
+      new_edge =
+        std::make_shared<Edge>(new_edge_name, op1, ith_edge->next_operator(), output_indexs, input_indexs, true);
+    } else {
+      size_t output_index, input_index;
+      output_index = ith_edge->prev_op_output_index();
+      input_index = ith_edge->next_op_input_index();
+      new_edge =
+        std::make_shared<Edge>(new_edge_name, op1, ith_edge->next_operator(), output_index, input_index, false);
+    }
+    new_edge->SetCostMapAndInputOutput(new_cost_map);
+    // replace the old successive edges with the new ones.
+    op1->ReplaceSuccEdge(ith_edge->next_operator(), new_edge);
+    ith_edge->next_operator()->ReplacePreEdge(op1, new_edge);
+    op1_new_succ_edges[i] = new_edge;
+  }
+  for (size_t i = 0; i < op2_old_succ_edges.size(); ++i) {
+    auto &new_cost_map = op2_new_edges_cost[i];
+    auto &ith_edge = op2_old_succ_edges[i];
+    const auto &destination = ith_edge->next_operator();
+
+    std::string new_edge_name = op1->name() + OPERATOR_TO_OPERATOR_CONNECTOR + destination->name();
+    std::shared_ptr<Edge> new_edge;
+    if (ith_edge->is_combined()) {
+      std::vector<size_t> output_indexs, input_indexs;
+      output_indexs = ith_edge->prev_op_output_indexs();
+      input_indexs = ith_edge->next_op_input_indexs();
+      new_edge = std::make_shared<Edge>(new_edge_name, op1, destination, output_indexs, input_indexs, true);
+    } else {
+      size_t output_index, input_index;
+      output_index = ith_edge->prev_op_output_index();
+      input_index = ith_edge->next_op_input_index();
+      new_edge = std::make_shared<Edge>(new_edge_name, op1, destination, output_index, input_index, false);
+    }
+    new_edge->SetCostMapAndInputOutput(new_cost_map);
+    // replace the old successive edges with the new ones.
+    destination->ReplacePreEdge(op2, new_edge);
+    op1->AddSuccEdge(new_edge);
+    op2_new_succ_edges[i] = new_edge;
+  }
+  MS_LOG(INFO) << "Source eliminating node: " << op2->name() << " to node: " << op1->name() + " succeeded.";
+  return {op1_new_succ_edges, op2_new_succ_edges};
+}
+
 // Check the graph whether a TriangleElimination can be performed
 std::pair<OperatorInfoPtr, std::shared_ptr<Edge>> CostGraph::CheckTriangleElimination() const {
   for (auto &op : ops_) {

mindspore/ccsrc/frontend/parallel/auto_parallel/graph_costmodel.h

@@ -180,6 +180,14 @@ class CostGraph {
   void CreateStarEliminationSubCostList(const StrategyPtr &, const CostPtrList &, const CostPtrList &,
                                         const StrategyPtr &, const CostPtrList &, std::vector<StrategyPtr>,
                                         CostPtrList &, CostPtrList &, CostPtrList *);
+  // Return <op1, op2>. we merge 'op2' into 'op1'
+  std::pair<OperatorInfoPtr, OperatorInfoPtr> CheckSourceElimination() const;
+  void CreateSourceEliminationSubCostList(StrategyPtr, const CostPtrList &, StrategyPtr, const CostPtrList &,
+                                          CostPtrList *);
+  // We merge 'op2' into op1. The returned value are '<Edges1, Edges2>'. 'Edges1' are newly updated edges for 'op1',
+  // 'Edges2' are newly updated edges for 'op2'.
+  std::pair<std::vector<std::shared_ptr<Edge>>, std::vector<std::shared_ptr<Edge>>> EliminationSources(
+    OperatorInfoPtr op1, OperatorInfoPtr op2);
   // Calculate memory cost for training phase or inference phase.
   Status CalculateMemoryCost();
   // When the input of a operator is neither a WEIGHT, nor a output of a subsequent operator involving WEIGHT, then

mindspore/ccsrc/frontend/parallel/ops_info/operator_info.cc

@@ -1330,5 +1330,9 @@ void OperatorInfo::CheckSelectedStrategy(const StrategyPtr &s_strategy) {
     PrintStrategy(s_strategy);
   }
 }
+
+void OperatorInfo::SetStrategyCost(const std::vector<std::shared_ptr<StrategyWithCost>> &stra_cost) {
+  strategy_cost_ = stra_cost;
+}
 }  // namespace parallel
 }  // namespace mindspore

mindspore/ccsrc/frontend/parallel/ops_info/operator_info.h

@@ -97,6 +97,7 @@ class OperatorInfo {
   // is checked
   Status SetCostUnderStrategyBase(const StrategyPtr &strategy);
   std::vector<std::shared_ptr<StrategyWithCost>> GetStrategyCost() { return strategy_cost_; }
+  void SetStrategyCost(const std::vector<std::shared_ptr<StrategyWithCost>> &);
   // In the training phase, when the input of a operator contains WEIGHT or a output from other operators involving
   // WEIGHT, then these input should stay in memory until it is used in the backward phase, which is kept in memory
   // at the end of forward phase.

mindspore/ccsrc/frontend/parallel/strategy.h

@@ -36,7 +36,19 @@ using StrategyPtr = std::shared_ptr<Strategy>;
 
 class Strategy {
  public:
-  Strategy(int32_t stage, std::vector<Dimensions> inputs) : stage_(stage), inputs_(std::move(inputs)) {}
+  Strategy(int32_t stage, std::vector<Dimensions> inputs)
+      : stage_(stage), inputs_(std::move(inputs)), internal_size_(0), internal_stragies_() {}
+
+  Strategy(const Strategy &another_stra) : stage_(another_stra.GetInputStage()) {
+    inputs_ = another_stra.GetInputDim();
+    internal_size_ = another_stra.GetInternalSize();
+    if (internal_size_ != 0) {
+      internal_stragies_ = another_stra.GetInternalStrategies();
+    } else {
+      internal_stragies_ = {};
+    }
+  }
+
   ~Strategy() = default;
   size_t GetInputNumber() const { return inputs_.size(); }
   std::vector<Dimensions> GetInputDim() const { return inputs_; }
@@ -47,7 +59,10 @@ class Strategy {
     }
   }
   void ResetInputs(const std::vector<Dimensions> &input) { inputs_ = input; }
+  std::vector<StrategyPtr> GetInternalStrategies() const { return internal_stragies_; }
+  size_t GetInternalSize() const { return internal_size_; }
 
+  // TODO(Xiaoda): need fix for adapting 'CoverStrategy'
   bool IsEqual(const StrategyPtr &another_stra) {
     if (another_stra == nullptr) {
       return false;
@@ -58,11 +73,19 @@ class Strategy {
     return true;
   }
 
+  // Include 'another_stra' into this strategy
+  void CoverStrategy(const StrategyPtr &another_stra) {
+    internal_stragies_.push_back(another_stra);
+    internal_size_++;
+  }
+
  private:
   const int32_t stage_;
 
   // The size of Dimensions must equal to inputs_ tensor dimension.
   std::vector<Dimensions> inputs_;
+  size_t internal_size_ = 0;
+  std::vector<StrategyPtr> internal_stragies_;
 };
 
 inline StrategyPtr NewStrategy(const int32_t stage, const std::vector<Dimensions> &inputs) {

tests/ut/python/parallel/test_auto_parallel_double_sources.py

@@ -0,0 +1,114 @@
+# Copyright 2020 Huawei Technologies Co., Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import numpy as np
+
+import mindspore as ms
+import mindspore.nn as nn
+from mindspore import Tensor
+from mindspore import context
+from mindspore.common.api import _executor
+from mindspore.ops import composite as C
+from mindspore.ops import operations as P
+from tests.ut.python.ops.test_math_ops import VirtualLoss
+
+
+class NetWithLoss(nn.Cell):
+    def __init__(self, network):
+        super(NetWithLoss, self).__init__()
+        self.loss = VirtualLoss()
+        self.network = network
+
+    def construct(self, x, y, z, w, a):
+        predict = self.network(x, y, z, w, a)
+        return self.loss(predict)
+
+
+class GradWrap(nn.Cell):
+    def __init__(self, network):
+        super(GradWrap, self).__init__()
+        self.network = network
+
+    def construct(self, x, y, z, w, a):
+        return C.grad_all(self.network)(x, y, z, w, a)
+
+    # model_parallel test
+
+
+def test_double_source_graph():
+    class Net(nn.Cell):
+        def __init__(self):
+            super().__init__()
+            self.matmul1 = P.MatMul()
+            self.matmul2 = P.MatMul()
+            self.matmul3 = P.MatMul()
+            self.matmul4 = P.MatMul()
+            self.matmul5 = P.MatMul()
+
+        def construct(self, x, y, z, w, a):
+            m1_result = self.matmul1(x, y)
+            m2_result = self.matmul2(z, w)
+            m3_result = self.matmul3(m2_result, m1_result)
+            m4_result = self.matmul4(m2_result, m1_result)
+            out = self.matmul5(m3_result, m4_result)
+
+            return out
+
+    size = 8
+    context.set_auto_parallel_context(device_num=size, global_rank=0)
+    x = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    y = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    z = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    w = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    a = Tensor(np.ones([32, 32]), dtype=ms.float32)
+
+    net = GradWrap(NetWithLoss(Net()))
+    context.set_auto_parallel_context(parallel_mode="auto_parallel")
+    net.set_auto_parallel()
+    _executor.compile(net, x, y, z, w, a)
+
+
+def test_double_source_complex_graph():
+    class Net(nn.Cell):
+        def __init__(self):
+            super().__init__()
+            self.matmul1 = P.MatMul()
+            self.matmul2 = P.MatMul()
+            self.matmul3 = P.MatMul()
+            self.matmul4 = P.MatMul()
+            self.matmul5 = P.MatMul()
+            self.matmul6 = P.MatMul()
+
+        def construct(self, x, y, z, w, a):
+            m1_result = self.matmul1(x, y)
+            m6_result = self.matmul6(m1_result, a)
+            m2_result = self.matmul2(z, w)
+            m3_result = self.matmul3(m2_result, m6_result)
+            m4_result = self.matmul4(m2_result, m1_result)
+            out = self.matmul5(m3_result, m4_result)
+
+            return out
+
+    size = 8
+    context.set_auto_parallel_context(device_num=size, global_rank=0)
+    x = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    y = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    z = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    w = Tensor(np.ones([32, 32]), dtype=ms.float32)
+    a = Tensor(np.ones([32, 32]), dtype=ms.float32)
+
+    net = GradWrap(NetWithLoss(Net()))
+    context.set_auto_parallel_context(parallel_mode="auto_parallel")
+    net.set_auto_parallel()
+    _executor.compile(net, x, y, z, w, a)