Revert "Subgraph API for integrating accelerators with MXNet (#12157)"

include/mxnet/engine.h

@@ -41,26 +41,8 @@ class Engine;
 
 /*! \brief namespace of engine internal types. */
 namespace engine {
-/*! \brief base class of engine variables.*/
-struct Var {
-  virtual size_t version() {
-    return version_;
-  }
-  virtual ~Var() = default;
-  /*!
-   * \brief cast variable to derived type T
-   * \tparam T the type we want to cast into.
-   * \return A casted variable.
-   */
-  template <typename T>
-  inline T* Cast();
-  /*!
-   * \brief version number of the var. Every time the object it is associated with
-   * is modified, the version number is incremented by 1.
-   */
-  size_t version_{0};
-};  // struct Var
-
+/*! \brief Internal representation of variable. */
+struct Var;
 /*! \brief Internal representation of operator.  */
 struct Opr;
 /*! \brief Variable pointer type, usually hold by user used to specify dependencies. */

include/mxnet/ndarray.h

@@ -340,10 +340,6 @@ class NDArray {
   inline size_t byte_offset() const {
     return byte_offset_;
   }
-  /*! \brief return var version of the NDArray*/
-  inline size_t version() const {
-    return var()->version();
-  }
   /*!
    * \brief save the content into binary stream
    * \param strm the output stream

src/engine/engine_impl.h

@@ -33,6 +33,20 @@
 namespace mxnet {
 namespace engine {
 
+/*! \brief base class of engine variables, used for type checking */
+struct Var {
+#if ENGINE_DEBUG
+  virtual ~Var() = default;
+#endif  // ENGINE_DEBUG
+  /*!
+   * \brief cast variable to derived type T
+   * \tparam T the type we want to cast into.
+   * \return A casted variable.
+   */
+  template <typename T>
+  inline T* Cast();
+};  // struct Var
+
 /*! \brief base class of engine operators, used for type checking */
 struct Opr {
 #if ENGINE_DEBUG

src/engine/naive_engine.cc

@@ -28,24 +28,10 @@
 #include "./engine_impl.h"
 #include "../profiler/profiler.h"
 #include "./openmp.h"
-#include "../common/object_pool.h"
 
 namespace mxnet {
 namespace engine {
 
-/*!
- * \brief var used in Naive Engine for tracking the version
- * of the objects it is associated with.
- */
-class NaiveVar final
-    : public Var, public common::ObjectPoolAllocatable<NaiveVar> {
- public:
-  inline static NaiveVar* CastFromBase(Var* ptr) {
-    return ptr->Cast<NaiveVar>();
-  }
-};  // class NaiveVar
-
-
 // implement naive engine
 class NaiveEngine final : public Engine {
  public:
@@ -85,7 +71,8 @@ class NaiveEngine final : public Engine {
 
   // new variables
   VarHandle NewVariable() override {
-    return NaiveVar::New();
+    size_t v = ++counter_;
+    return reinterpret_cast<VarHandle>(v);
   }
 
   OprHandle NewOperator(AsyncFn fn,
@@ -159,10 +146,6 @@ class NaiveEngine final : public Engine {
       opr->opr_profile.reset(new profiler::ProfileOperator(opr->opr_name, attrs.release()));
       opr->opr_profile->start(exec_ctx.dev_type, exec_ctx.dev_id);
     }
-    // increment mutable var version
-    for (auto var : mutable_vars) {
-      ++var->version_;
-    }
     if (exec_ctx.dev_mask() == gpu::kDevMask) {
 #if MXNET_USE_CUDA
       size_t dev_id = static_cast<size_t>(exec_ctx.dev_id);
@@ -188,12 +171,8 @@ class NaiveEngine final : public Engine {
   }
 
   void DeleteVariable(SyncFn delete_fn, Context exec_ctx, VarHandle var) override {
-    NaiveVar* naive_var = NaiveVar::CastFromBase(var);
-    this->PushAsync([delete_fn, naive_var](RunContext ctx, CallbackOnComplete on_complete) mutable {
-        delete_fn(ctx);
-        NaiveVar::Delete(naive_var);
-        on_complete();
-      }, exec_ctx, {}, {var}, FnProperty::kDeleteVar, 0, "DeleteVariable");
+    this->PushSync(delete_fn, exec_ctx, {}, {var},
+                   FnProperty::kNormal, 0, "DeleteVariable");
   }
 
   void WaitForVar(VarHandle var) override {
@@ -213,6 +192,8 @@ class NaiveEngine final : public Engine {
   }
   // whether action is completed
   bool req_completed_;
+  // counter
+  std::atomic<size_t> counter_{0};
   /*! \brief whether it is during shutdown phase*/
   std::atomic<bool> shutdown_phase_{false};
   // CPU stream

src/engine/threaded_engine.cc

@@ -130,9 +130,6 @@ inline bool ThreadedVar::CompleteWriteDependency(Dispatcher dispatcher) {
     assert(pending_write_ != nullptr);
     CHECK_EQ(num_pending_reads_, kWriteTriggered);
 
-    // increment version number
-    ++version_;
-
     // really delete
     if (to_delete_) {
       VersionedVarBlock *head = pending_write_->next;
@@ -167,7 +164,7 @@ inline bool ThreadedVar::CompleteWriteDependency(Dispatcher dispatcher) {
   }
   // This is outside of lock scope
   // Be very carful, pending_write_ and num_pending_reads_
-  // can change now, do not rely on these two variables.
+  // can change now, do not reply ont the two variables.
   // The linked list \in [old_pending_write, end_of_read_chain)
   // is already detached from this Var.
   // So it is safe to modify these
@@ -199,11 +196,6 @@ inline bool ThreadedVar::ready_to_read() {
   return this->is_ready_to_read();
 }
 
-inline size_t ThreadedVar::version() {
-  std::lock_guard<std::mutex> lock{mutex_};
-  return this->version_;
-}
-
 // implementation of threaded engine
 ThreadedVar* ThreadedEngine::NewVariable() {
   return ThreadedVar::New(VersionedVarBlock::New());

src/engine/threaded_engine.h

@@ -162,7 +162,6 @@ class ThreadedVar final
   inline void SetToDelete();
   /*! \return whether this variable is ready to read. */
   inline bool ready_to_read();
-  inline size_t version() override;
   /*!
    * \brief Cast a Var pointer to ThreadedVar pointer
    * \param ptr pointer from base.