[async] Add element-wise info into TaskMeta for fusion (#1884)

* Refactor AsyncStateHash to std::hash * Add TaskMeta::element_wise * Make use of it in fuse() * Fix false positive when task type is serial * [skip ci] Apply suggestions from code review Co-authored-by: Yuanming Hu <yuanming-hu@users.noreply.github.com> * [skip ci] enforce code format * retrigger CI Co-authored-by: Yuanming Hu <yuanming-hu@users.noreply.github.com> Co-authored-by: Taichi Gardener <taichigardener@gmail.com>
taichi-dev · Sep 21, 2020 · 9a23ecd · 9a23ecd
1 parent f2a798d
commit 9a23ecd
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Showing 7 changed files with 120 additions and 43 deletions.
diff --git a/taichi/ir/ir.cpp b/taichi/ir/ir.cpp
@@ -406,6 +406,28 @@ GlobalPtrStmt::GlobalPtrStmt(const LaneAttribute<SNode *> &snodes,
   TI_STMT_REG_FIELDS;
 }
 
+bool GlobalPtrStmt::is_element_wise(SNode *snode) const {
+  if (snode == nullptr) {
+    // check every SNode when "snode" is nullptr
+    for (const auto &snode_i : snodes.data) {
+      if (!is_element_wise(snode_i)) {
+        return false;
+      }
+    }
+    return true;
+  }
+  // check if this statement is element-wise on a specific SNode, i.e., argument
+  // "snode"
+  for (int i = 0; i < (int)indices.size(); i++) {
+    if (auto loop_index_i = indices[i]->cast<LoopIndexStmt>();
+        !(loop_index_i && loop_index_i->loop->is<OffloadedStmt>() &&
+          loop_index_i->index == snode->physical_index_position[i])) {
+      return false;
+    }
+  }
+  return true;
+}
+
 std::string GlobalPtrExpression::serialize() {
   std::string s = fmt::format("{}[", var.serialize());
   for (int i = 0; i < (int)indices.size(); i++) {

diff --git a/taichi/ir/ir.h b/taichi/ir/ir.h
@@ -851,6 +851,8 @@ class GlobalPtrStmt : public Stmt {
                 const std::vector<Stmt *> &indices,
                 bool activate = true);
 
+  bool is_element_wise(SNode *snode) const;
+
   bool has_global_side_effect() const override {
     return activate;
   }

diff --git a/taichi/program/async_engine.cpp b/taichi/program/async_engine.cpp
@@ -362,6 +362,15 @@ TaskMeta *get_task_meta(IRBank *ir_bank, const TaskLaunchRecord &t) {
           }
         }
       }
+      for (auto &snode : ptr->snodes.data) {
+        if (ptr->is_element_wise(snode)) {
+          if (meta.element_wise.find(snode) == meta.element_wise.end()) {
+            meta.element_wise[snode] = true;
+          }
+        } else {
+          meta.element_wise[snode] = false;
+        }
+      }
     }
     if (auto clear_list = stmt->cast<ClearListStmt>()) {
       meta.output_states.emplace(clear_list->snode, AsyncState::Type::list);

diff --git a/taichi/program/async_utils.cpp b/taichi/program/async_utils.cpp
@@ -55,6 +55,28 @@ void TaskMeta::print() const {
     }
     fmt::print("\n");
   }
+  std::vector<SNode *> element_wise_snodes, non_element_wise_snodes;
+  for (auto s : element_wise) {
+    if (s.second) {
+      element_wise_snodes.push_back(s.first);
+    } else {
+      non_element_wise_snodes.push_back(s.first);
+    }
+  }
+  if (!element_wise_snodes.empty()) {
+    fmt::print("  element-wise snodes:\n    ");
+    for (auto s : element_wise_snodes) {
+      fmt::print("{} ", s->get_node_type_name_hinted());
+    }
+    fmt::print("\n");
+  }
+  if (!non_element_wise_snodes.empty()) {
+    fmt::print("  non-element-wise snodes:\n    ");
+    for (auto s : non_element_wise_snodes) {
+      fmt::print("{} ", s->get_node_type_name_hinted());
+    }
+    fmt::print("\n");
+  }
 }
 
 TLANG_NAMESPACE_END
diff --git a/taichi/program/async_utils.h b/taichi/program/async_utils.h
@@ -50,29 +50,6 @@ class IRHandle {
   uint64 hash_;
 };
 
-TLANG_NAMESPACE_END
-
-namespace std {
-template <>
-struct hash<taichi::lang::IRHandle> {
-  std::size_t operator()(const taichi::lang::IRHandle &ir_handle) const
-      noexcept {
-    return ir_handle.hash();
-  }
-};
-
-template <>
-struct hash<std::pair<taichi::lang::IRHandle, taichi::lang::IRHandle>> {
-  std::size_t operator()(
-      const std::pair<taichi::lang::IRHandle, taichi::lang::IRHandle>
-          &ir_handles) const noexcept {
-    return ir_handles.first.hash() * 100000007UL + ir_handles.second.hash();
-  }
-};
-}  // namespace std
-
-TLANG_NAMESPACE_BEGIN
-
 // Records the necessary data for launching an offloaded task.
 class TaskLaunchRecord {
  public:
@@ -127,19 +104,44 @@ struct AsyncState {
   }
 };
 
-class AsyncStateHash {
- public:
-  size_t operator()(const AsyncState &s) const {
-    return (uint64)s.snode ^ (uint64)s.type;
+TLANG_NAMESPACE_END
+
+namespace std {
+template <>
+struct hash<taichi::lang::IRHandle> {
+  std::size_t operator()(const taichi::lang::IRHandle &ir_handle) const
+      noexcept {
+    return ir_handle.hash();
+  }
+};
+
+template <>
+struct hash<std::pair<taichi::lang::IRHandle, taichi::lang::IRHandle>> {
+  std::size_t operator()(
+      const std::pair<taichi::lang::IRHandle, taichi::lang::IRHandle>
+          &ir_handles) const noexcept {
+    return ir_handles.first.hash() * 100000007UL + ir_handles.second.hash();
+  }
+};
+
+template <>
+struct hash<taichi::lang::AsyncState> {
+  std::size_t operator()(const taichi::lang::AsyncState &s) const noexcept {
+    return (std::size_t)s.snode ^ (std::size_t)s.type;
   }
 };
 
+}  // namespace std
+
+TLANG_NAMESPACE_BEGIN
+
 struct TaskMeta {
   std::string name;
   OffloadedStmt::TaskType type{OffloadedStmt::TaskType::serial};
   SNode *snode{nullptr};  // struct-for and listgen only
-  std::unordered_set<AsyncState, AsyncStateHash> input_states;
-  std::unordered_set<AsyncState, AsyncStateHash> output_states;
+  std::unordered_set<AsyncState> input_states;
+  std::unordered_set<AsyncState> output_states;
+  std::unordered_map<SNode *, bool> element_wise;
 
   void print() const;
 };

diff --git a/taichi/program/state_flow_graph.cpp b/taichi/program/state_flow_graph.cpp
@@ -235,11 +235,11 @@ bool StateFlowGraph::fuse() {
   std::vector<Bitset> has_path, has_path_reverse;
   std::tie(has_path, has_path_reverse) = compute_transitive_closure();
 
-  // Cache the result that if each pair is fusable by task types.
+  // Cache the result that if each pair is fusible by task types.
   // TODO: improve this
-  auto task_type_fusable = std::make_unique<Bitset[]>(n);
+  auto task_type_fusible = std::make_unique<Bitset[]>(n);
   for (int i = 0; i < n; i++) {
-    task_type_fusable[i] = Bitset(n);
+    task_type_fusible[i] = Bitset(n);
   }
   // nodes_[0] is the initial node.
   for (int i = 1; i < n; i++) {
@@ -292,10 +292,10 @@ bool StateFlowGraph::fuse() {
       // TODO: avoid snode accessors going into async engine
       const bool is_snode_accessor =
           (rec_i.kernel->is_accessor || rec_j.kernel->is_accessor);
-      bool fusable =
+      bool fusible =
           (is_same_range_for || is_same_struct_for || are_both_serial) &&
           kernel_args_match && !is_snode_accessor;
-      task_type_fusable[i][j] = fusable;
+      task_type_fusible[i][j] = fusible;
     }
   }
 
@@ -345,6 +345,29 @@ bool StateFlowGraph::fuse() {
 
   auto fused = std::make_unique<bool[]>(n);
 
+  auto edge_fusible = [&](int a, int b) {
+    // Check if a and b are fusible if there is an edge (a, b).
+    if (fused[a] || fused[b] || !task_type_fusible[a][b]) {
+      return false;
+    }
+    if (nodes_[a]->meta->type == OffloadedStmt::TaskType::serial) {
+      return true;
+    }
+    for (auto &state : nodes_[a]->output_edges) {
+      if (state.first.type != AsyncState::Type::value) {
+        // TODO: What checks do we need for edges of mask/list states?
+        continue;
+      }
+      if (state.second.find(nodes_[b].get()) != state.second.end()) {
+        if (!nodes_[a]->meta->element_wise[state.first.snode] ||
+            !nodes_[b]->meta->element_wise[state.first.snode]) {
+          return false;
+        }
+      }
+    }
+    return true;
+  };
+
   bool modified = false;
   while (true) {
     bool updated = false;
@@ -357,9 +380,7 @@ bool StateFlowGraph::fuse() {
         for (auto &edges : nodes_[i]->output_edges) {
           for (auto &edge : edges.second) {
             const int j = edge->node_id;
-            // TODO: for each pair of edge (i, j), we can only fuse if they
-            // are both serial or both element-wise.
-            if (!fused[j] && task_type_fusable[i][j]) {
+            if (edge_fusible(i, j)) {
               auto i_has_path_to_j = has_path[i] & has_path_reverse[j];
               i_has_path_to_j[i] = i_has_path_to_j[j] = false;
               // check if i doesn't have a path to j of length >= 2
@@ -381,7 +402,7 @@ bool StateFlowGraph::fuse() {
     for (int i = 1; i < n; i++) {
       if (!fused[i]) {
         for (int j = i + 1; j < n; j++) {
-          if (!fused[j] && task_type_fusable[i][j] && !has_path[i][j] &&
+          if (!fused[j] && task_type_fusible[i][j] && !has_path[i][j] &&
               !has_path[j][i]) {
             do_fuse(i, j);
             fused[i] = fused[j] = true;

diff --git a/taichi/program/state_flow_graph.h b/taichi/program/state_flow_graph.h
@@ -18,8 +18,7 @@ class IRBank;
 class StateFlowGraph {
  public:
   struct Node;
-  using StateToNodeMapping =
-      std::unordered_map<AsyncState, Node *, AsyncStateHash>;
+  using StateToNodeMapping = std::unordered_map<AsyncState, Node *>;
 
   // Each node is a task
   // Note: after SFG is done, each node here should hold a TaskLaunchRecord.
@@ -39,8 +38,8 @@ class StateFlowGraph {
 
     // Profiling showed horrible performance using std::unordered_multimap (at
     // least on Mac with clang-1103.0.32.62)...
-    std::unordered_map<AsyncState, std::unordered_set<Node *>, AsyncStateHash>
-        output_edges, input_edges;
+    std::unordered_map<AsyncState, std::unordered_set<Node *>> output_edges,
+        input_edges;
 
     std::string string() const;
 
@@ -140,7 +139,7 @@ class StateFlowGraph {
   Node *initial_node_;  // The initial node holds all the initial states.
   TaskMeta initial_meta_;
   StateToNodeMapping latest_state_owner_;
-  std::unordered_map<AsyncState, std::unordered_set<Node *>, AsyncStateHash>
+  std::unordered_map<AsyncState, std::unordered_set<Node *>>
       latest_state_readers_;
   std::unordered_map<std::string, int> task_name_to_launch_ids_;
   IRBank *ir_bank_;