refactor to avoid scope.

test=develop

paddle/fluid/framework/operator.cc

@@ -180,6 +180,11 @@ void OperatorBase::Run(const Scope& scope, const platform::Place& place) {
   VLOG(3) << place << " " << DebugStringEx(&scope);
 }
 
+void OperatorBase::Run(const RuntimeContext& ctx,
+                       const platform::Place& place) {
+  RunImpl(ctx, place);
+}
+
 bool OperatorBase::HasInputs(const std::string& name) const {
   return inputs_.find(name) != inputs_.end();
 }
@@ -954,6 +959,51 @@ void OperatorWithKernel::RunImpl(const Scope& scope,
   }
 }
 
+void OperatorWithKernel::RunImpl(const RuntimeContext& ctx,
+                                 const platform::Place& place) const {
+  Scope scope;
+  platform::DeviceContextPool& pool = platform::DeviceContextPool::Instance();
+  auto* dev_ctx = pool.Get(place);
+
+  // check if op[type] has kernel registered.
+  auto& all_op_kernels = AllOpKernels();
+  auto kernels_iter = all_op_kernels.find(type_);
+  if (kernels_iter == all_op_kernels.end()) {
+    PADDLE_THROW(
+        "There are no kernels which are registered in the %s operator.", type_);
+  }
+
+  OpKernelMap& kernels = kernels_iter->second;
+
+  auto expected_kernel_key = this->GetExpectedKernelType(
+      ExecutionContext(*this, scope, *dev_ctx, ctx));
+  VLOG(3) << "expected_kernel_key:" << expected_kernel_key;
+
+  auto kernel_iter = kernels.find(expected_kernel_key);
+#ifdef PADDLE_WITH_MKLDNN
+  // workaround for missing MKLDNN kernel when FLAGS_use_mkldnn env var is set
+  if (kernel_iter == kernels.end() &&
+      expected_kernel_key.library_type_ == LibraryType::kMKLDNN) {
+    VLOG(3) << "missing MKLDNN kernel: fallbacking to PLAIN one";
+    expected_kernel_key.library_type_ = LibraryType::kPlain;
+    expected_kernel_key.data_layout_ = DataLayout::kAnyLayout;
+    kernel_iter = kernels.find(expected_kernel_key);
+  }
+#endif
+  if (kernel_iter == kernels.end()) {
+    PADDLE_THROW("op %s does not have kernel for %s", type_,
+                 KernelTypeToString(expected_kernel_key));
+  }
+
+  if (!(expected_kernel_key.place_ == dev_ctx->GetPlace())) {
+    dev_ctx = pool.Get(expected_kernel_key.place_);
+  }
+
+  RuntimeInferShapeContext infer_shape_ctx(*this, scope, ctx);
+  this->InferShape(&infer_shape_ctx);
+  kernel_iter->second(ExecutionContext(*this, scope, *dev_ctx, ctx));
+}
+
 void OperatorWithKernel::TransferInplaceVarsBack(
     const Scope& scope, const std::vector<std::string>& inplace_vars,
     const Scope& transfer_scope) const {
@@ -1041,12 +1091,9 @@ Scope* OperatorWithKernel::PrepareData(
 
 proto::VarType::Type OperatorWithKernel::IndicateDataType(
     const ExecutionContext& ctx) const {
-  auto& scope = ctx.scope();
   int data_type = -1;
-  std::string last_input_name;
   for (auto& input : this->inputs_) {
-    for (auto& ipt_name : input.second) {
-      auto* var = scope.FindVar(ipt_name);
+    for (const Variable* var : ctx.MultiInputVar(input.first)) {
       if (var != nullptr) {
         const Tensor* t = nullptr;
         if (var->IsType<Tensor>()) {
@@ -1062,10 +1109,9 @@ proto::VarType::Type OperatorWithKernel::IndicateDataType(
           int tmp = static_cast<int>(t->type());
           PADDLE_ENFORCE(
               tmp == data_type || data_type == -1,
-              "DataType of Paddle Op %s must be the same. Get %s(%d) != %s(%d)",
-              Type(), last_input_name, data_type, ipt_name, tmp);
+              "DataType of Paddle Op %s must be the same. Get (%d) != (%d)",
+              Type(), data_type, tmp);
           data_type = tmp;
-          last_input_name = ipt_name;
         }
       }
     }

paddle/fluid/framework/operator.h

@@ -81,6 +81,10 @@ class RuntimeContext {
   RuntimeContext(const VariableNameMap& innames,
                  const VariableNameMap& outnames, const Scope& scope);
 
+  RuntimeContext(const VariableValueMap& invars,
+                 const VariableValueMap& outvars)
+      : inputs(invars), outputs(outvars) {}
+
   VariableValueMap inputs;
   VariableValueMap outputs;
 };
@@ -101,6 +105,7 @@ class OperatorBase {
   /// Executor will call this interface function to Run an op.
   //  The implementation should be written at RunImpl
   void Run(const Scope& scope, const platform::Place& place);
+  void Run(const RuntimeContext& ctx, const platform::Place& place);
 
   // FIXME(typhoonzero): this is only used for recv_op to stop event_loop.
   virtual void Stop() {}
@@ -167,6 +172,9 @@ class OperatorBase {
   void CheckAllInputOutputSet() const;
   virtual void RunImpl(const Scope& scope,
                        const platform::Place& place) const = 0;
+
+  virtual void RunImpl(const RuntimeContext& ctx,
+                       const platform::Place& place) const {}
 };
 
 class ExecutionContext {
@@ -458,6 +466,8 @@ class OperatorWithKernel : public OperatorBase {
   // same.
   proto::VarType::Type IndicateDataType(const ExecutionContext& ctx) const;
   void RunImpl(const Scope& scope, const platform::Place& place) const final;
+  void RunImpl(const RuntimeContext& ctx,
+               const platform::Place& place) const final;
 
   /**
    * Transfer data from scope to a transfered scope. If there is no data need to

paddle/fluid/imperative/layer.cc

@@ -31,6 +31,11 @@ using framework::Variable;
 void AddTo(Variable* src, Variable* dst) {
   framework::LoDTensor* dst_tensor = dst->GetMutable<framework::LoDTensor>();
   framework::LoDTensor* src_tensor = src->GetMutable<framework::LoDTensor>();
+
+  VLOG(3) << "apply var grad " << src_tensor->data<float>()[0] << " "
+          << src_tensor->data<float>()[1] << " "
+          << src_tensor->data<float>()[2];
+
   PADDLE_ENFORCE(dst_tensor->numel() == src_tensor->numel(), "%lld vs %lld",
                  dst_tensor->numel(), src_tensor->numel());
   float* dst_data = dst_tensor->mutable_data<float>(platform::CPUPlace());
@@ -38,16 +43,28 @@ void AddTo(Variable* src, Variable* dst) {
   for (size_t i = 0; i < src_tensor->numel(); ++i) {
     dst_data[i] += src_data[i];
   }
+
+  VLOG(3) << "apply var dst grad " << dst_tensor->data<float>()[0] << " "
+          << dst_tensor->data<float>()[1] << " "
+          << dst_tensor->data<float>()[2];
 }
 
 class Autograd {
  public:
-  explicit Autograd(framework::Scope* scope) : scope_(scope) {}
+  Autograd() {}
 
   void RunBackward(VarBase* var) {
     PADDLE_ENFORCE(var->pre_op_->op_desc_);
     // TODO(panyx0718): Only create for vars that "require_grad"
-    (*var->pre_op_->output_vars_)[var->pre_op_out_idx_]->grads_ = var->grads_;
+    LOG(ERROR) << reinterpret_cast<void*>(var->grads_) << " vs "
+               << reinterpret_cast<void*>(
+                      var->pre_op_
+                          ->output_vars_[var->pre_op_out_name_]
+                                        [var->pre_op_out_idx_]
+                          ->grads_);
+    var->pre_op_->output_vars_[var->pre_op_out_name_][var->pre_op_out_idx_]
+        ->grads_->GetMutable<framework::LoDTensor>()
+        ->ShareDataWith(var->grads_->Get<framework::LoDTensor>());
 
     std::deque<OpBase*> ready;
     ready.push_back(var->pre_op_);
@@ -57,18 +74,23 @@ class Autograd {
     while (!ready.empty()) {
       OpBase* ready_op = ready.front();
       ready.pop_front();
-      std::vector<Variable*> input_grads = ready_op->ApplyGrad(scope_);
-
-      for (size_t i = 0; i < input_grads.size(); ++i) {
-        if (!input_grads[i]) continue;
-        OpBase* pre_op = ready_op->pre_ops_->at(i);
-        if (!pre_op) continue;
-
-        dep_counts[pre_op] -= 1;
-        PADDLE_ENFORCE(dep_counts[pre_op] >= 0);
-        bool pre_op_ready = dep_counts[pre_op] == 0;
-        if (pre_op_ready) {
-          ready.push_back(pre_op);
+      std::map<std::string, std::vector<VarBase*>> input_grads =
+          ready_op->ApplyGrad();
+      VLOG(3) << "after apply grad";
+
+      for (auto it : input_grads) {
+        const std::vector<VarBase*>& ingrads = it.second;
+        for (size_t i = 0; i < ingrads.size(); ++i) {
+          if (!ingrads[i]) continue;
+          OpBase* pre_op = (*ready_op->pre_ops_)[it.first][i];
+          if (!pre_op) continue;
+
+          dep_counts[pre_op] -= 1;
+          PADDLE_ENFORCE(dep_counts[pre_op] >= 0);
+          bool pre_op_ready = dep_counts[pre_op] == 0;
+          if (pre_op_ready) {
+            ready.push_back(pre_op);
+          }
         }
       }
     }
@@ -85,26 +107,25 @@ class Autograd {
     while (!queue.empty()) {
       OpBase* candidate = queue.front();
       queue.pop_front();
-      for (OpBase* pre_op : *(candidate->pre_ops_)) {
-        if (!pre_op) continue;
-        if (visited.find(pre_op) == visited.end()) {
-          visited.insert(pre_op);
-          queue.push_back(pre_op);
+      for (auto it : *(candidate->pre_ops_)) {
+        for (OpBase* pre_op : it.second) {
+          if (!pre_op) continue;
+          if (visited.find(pre_op) == visited.end()) {
+            visited.insert(pre_op);
+            queue.push_back(pre_op);
+          }
+          ret[pre_op] += 1;
         }
-        ret[pre_op] += 1;
       }
     }
-
     return ret;
   }
-
-  framework::Scope* scope_;
 };
 
-framework::Variable* CreateVariable(const std::string& name,
-                                    const framework::DDim& dim, float val,
-                                    framework::Scope* scope,
-                                    bool random_name = true) {
+void CreateVariable(const std::string& name, const framework::DDim& dim,
+                    float val, bool random_name, framework::Variable* var) {
+  if (var->IsInitialized()) return;
+
   std::string varname = name;
   if (random_name) {
     std::mt19937 rng;
@@ -116,12 +137,9 @@ framework::Variable* CreateVariable(const std::string& name,
   }
 
   VLOG(3) << "creating var " << varname;
-  framework::Variable* var = scope->Var(varname);
   framework::LoDTensor* tensor = var->GetMutable<framework::LoDTensor>();
-
   float* data = tensor->mutable_data<float>(dim, platform::CPUPlace());
   std::fill(data, data + tensor->numel(), val);
-  return var;
 }
 
 framework::LoDTensor& VarBase::Grad() {
@@ -129,94 +147,56 @@ framework::LoDTensor& VarBase::Grad() {
   return *grads_->GetMutable<framework::LoDTensor>();
 }
 
-void VarBase::ApplyGrad(framework::Scope* scope, Variable* grad) {
-  VLOG(3) << "apply var grad " << var_desc_->Name() << " "
-          << grad->Get<framework::LoDTensor>().data<float>()[0];
-  if (!grads_) {
-    grads_ =
-        CreateVariable(string::Sprintf("%s@IGrad", var_desc_->Name()),
-                       var_->Get<framework::LoDTensor>().dims(), 0.0, scope);
+std::map<std::string, std::vector<VarBase*>> OpBase::ApplyGrad() {
+  if (!grad_op_desc_) {
+    VLOG(3) << "op with no grad: " << op_desc_->Type();
+    return {};
   }
-  AddTo(grad, grads_);
-  VLOG(3) << "grad_ after apply var grad " << var_desc_->Name() << " "
-          << grads_->Get<framework::LoDTensor>().data<float>()[0];
-}
-
-std::vector<Variable*> OpBase::ApplyGrad(framework::Scope* scope) {
   VLOG(3) << "op grad " << grad_op_desc_->Type();
 
-  for (const std::string& grad_invar : grad_op_desc_->InputArgumentNames()) {
-    if (grad_to_var_->find(grad_invar) == grad_to_var_->end()) {
-      // grad op inputs can be forward inputs, so not in grad_to_var.
-      continue;
-    }
-    VLOG(3) << "op grad in var " << grad_invar;
-    block_->FindRecursiveOrCreateVar(grad_invar);
-    framework::Variable* var = scope->Var(grad_invar);
-    const std::string& invar = grad_to_var_->at(grad_invar);
-    for (VarBase* varbase : *output_vars_) {
-      // Use the accumulated grads_ by sharing the input with grads_.
-      if (varbase->var_desc_->Name() == invar) {
-        var->GetMutable<framework::LoDTensor>()->ShareDataWith(
-            varbase->grads_->Get<framework::LoDTensor>());
-        break;
-      }
+  std::map<std::string, std::vector<framework::Variable*>> grad_outputs;
+  for (auto it : grad_output_vars_) {
+    auto& outputs = grad_outputs[it.first];
+    for (size_t i = 0; i < it.second.size(); ++i) {
+      outputs.push_back(new framework::Variable());
+      outputs.back()->GetMutable<framework::LoDTensor>();
+      /*
+      auto& accum_grad_t = it.second[i]->Get<framework::LoDTensor>();
+      Variable* grad_var = outputs.back();
+      float* data = grad_var->GetMutable<framework::LoDTensor>()
+          ->mutable_data<float>(accum_grad_t.dims(), platform::CPUPlace());
+      std::fill(data, data + accum_grad_t.numel(), 0.0);*/
     }
   }
 
-  for (const std::string& outvar : grad_op_desc_->OutputArgumentNames()) {
-    VLOG(3) << "grad outvar " << outvar;
-    block_->FindRecursiveOrCreateVar(outvar);
-    framework::Variable* var = scope->Var(outvar);
-    if (!var->IsInitialized()) {
-      framework::VarDesc* var_desc = block_->FindVar(outvar);
-      if (var_desc->GetType() == framework::proto::VarType::LOD_TENSOR) {
-        var->GetMutable<framework::LoDTensor>();
-      } else {
-        LOG(ERROR) << "tracer doesn't support yet";
-      }
-    }
-  }
-  grad_op_desc_->InferShape(*block_);
+  framework::RuntimeContext ctx(grad_input_vars_, grad_outputs);
+
+  // grad_op_desc_->InferShape(*block_);
   grad_op_desc_->InferVarType(block_);
+
   std::unique_ptr<framework::OperatorBase> opbase =
       framework::OpRegistry::CreateOp(*grad_op_desc_);
-
-  opbase->Run(*scope, platform::CPUPlace());
-
-  // `ret` matches exactly with `input_vars_` of forward op.
-  std::vector<Variable*> ret;
-  for (size_t i = 0; i < input_vars_->size(); ++i) {
-    bool found = false;
-    VarBase* origin_var = (*input_vars_)[i];
-    for (const std::string& outvar : grad_op_desc_->OutputArgumentNames()) {
-      Variable* var = scope->FindVar(outvar);
-      std::string orig_var = grad_to_var_->at(outvar);
-      if (origin_var->var_desc_->Name() != orig_var) {
-        continue;
-      }
-      VLOG(3) << "apply grad " << outvar << " with origin " << orig_var;
-      origin_var->ApplyGrad(scope, var);
-      found = true;
-      ret.push_back(var);
-      // TODO(panyx0718): There might be another outvar with the same name.
-      // In that case, it doesn't matter the first one or the second one is
-      // used.
-      break;
-    }
-    if (!found) {
-      ret.push_back(nullptr);
+  opbase->Run(ctx, platform::CPUPlace());
+
+  for (auto it : grad_output_vars_) {
+    auto& outputs = grad_outputs[it.first];
+    auto& origin_outputs = it.second;
+    for (size_t i = 0; i < outputs.size(); ++i) {
+      framework::Variable* orig_grad = origin_outputs[i];
+      AddTo(outputs[i], orig_grad);
+      VLOG(3) << "done add to " << grad_op_desc_->Outputs().at(it.first)[i];
     }
   }
-  return ret;
+  return input_vars_;
 }
 
-void VarBase::RunBackward(framework::Scope* scope) {
-  grads_ = CreateVariable(framework::GradVarName(var_desc_->Name()),
-                          var_->Get<framework::LoDTensor>().dims(), 1.0, scope,
-                          false);
+void VarBase::RunBackward() {
+  auto grads_t = grads_->GetMutable<framework::LoDTensor>();
+  float* data = grads_t->mutable_data<float>(platform::CPUPlace());
+  std::fill(data, data + grads_t->numel(), 1.0);
+
   if (!pre_op_) return;
-  Autograd(scope).RunBackward(this);
+  Autograd().RunBackward(this);
 }
 
 }  // namespace imperative

paddle/fluid/imperative/layer.h

@@ -14,11 +14,11 @@
 
 #pragma once
 
+#include <map>
 #include <string>
 #include <vector>
 #include "paddle/fluid/framework/op_desc.h"
 #include "paddle/fluid/framework/operator.h"
-#include "paddle/fluid/framework/scope.h"
 #include "paddle/fluid/framework/var_desc.h"
 #include "paddle/fluid/platform/enforce.h"
 
@@ -33,18 +33,26 @@ class VarBase {
       : pre_op_(nullptr),
         pre_op_out_idx_(-1),
         var_desc_(nullptr),
-        var_(nullptr),
-        grads_(nullptr) {}
-
-  virtual ~VarBase() {}
-
-  void ApplyGrad(framework::Scope* scope, framework::Variable* grad);
+        var_(new framework::Variable()),
+        grads_(new framework::Variable()) {}
+
+  virtual ~VarBase() {
+    if (var_) {
+      delete var_;
+      var_ = nullptr;
+    }
+    if (grads_) {
+      delete grads_;
+      grads_ = nullptr;
+    }
+  }
 
-  void RunBackward(framework::Scope* scope);
+  void RunBackward();
 
   framework::LoDTensor& Grad();
 
   OpBase* pre_op_;
+  std::string pre_op_out_name_;
   int pre_op_out_idx_;
 
   framework::VarDesc* var_desc_;
@@ -55,17 +63,12 @@ class VarBase {
 class OpBase {
  public:
   OpBase()
-      : input_vars_(new std::vector<VarBase*>()),
-        output_vars_(new std::vector<VarBase*>()),
-        pre_ops_(new std::vector<OpBase*>()),
-        pre_ops_out_idx_(new std::vector<int>()),
+      : pre_ops_(new std::map<std::string, std::vector<OpBase*>>()),
+        pre_ops_out_idx_(new std::map<std::string, std::vector<int>>()),
         op_desc_(nullptr),
         grad_op_desc_(nullptr) {}
 
   virtual ~OpBase() {
-    delete input_vars_;
-    delete output_vars_;
-
     delete pre_ops_;
     delete pre_ops_out_idx_;
 
@@ -73,16 +76,18 @@ class OpBase {
     if (grad_to_var_) delete grad_to_var_;
   }
 
-  std::vector<framework::Variable*> ApplyGrad(framework::Scope* scope);
+  std::map<std::string, std::vector<VarBase*>> ApplyGrad();
 
-  std::vector<VarBase*>* input_vars_;
-  std::vector<VarBase*>* output_vars_;
-  std::vector<OpBase*>* pre_ops_;
-  std::vector<int>* pre_ops_out_idx_;
+  std::map<std::string, std::vector<VarBase*>> input_vars_;
+  std::map<std::string, std::vector<VarBase*>> output_vars_;
+  std::map<std::string, std::vector<OpBase*>>* pre_ops_;
+  std::map<std::string, std::vector<int>>* pre_ops_out_idx_;
   framework::OpDesc* op_desc_;
 
   framework::OpDesc* grad_op_desc_;
   std::unordered_map<std::string, std::string>* grad_to_var_;
+  std::map<std::string, std::vector<framework::Variable*>> grad_input_vars_;
+  std::map<std::string, std::vector<framework::Variable*>> grad_output_vars_;
   framework::BlockDesc* block_;
 };
 

paddle/fluid/imperative/tracer.h

@@ -41,6 +41,14 @@ void CreateGradOp(const framework::OpDesc& op_desc,
   *grad_op_desc = grad_op_descs[0].release();
 }
 
+void InitVar(framework::Variable* var, framework::Variable* grad_var) {
+  auto& var_t = var->Get<framework::LoDTensor>();
+  float* data =
+      grad_var->GetMutable<framework::LoDTensor>()->mutable_data<float>(
+          var_t.dims(), platform::CPUPlace());
+  std::fill(data, data + var_t.numel(), 0.0);
+}
+
 class Tracer {
  public:
   explicit Tracer(framework::BlockDesc* root_block,
@@ -53,10 +61,13 @@ class Tracer {
 
   virtual ~Tracer() { delete root_scope_; }
 
-  void Trace(OpBase* op, const std::vector<VarBase*>& inputs,
-             const std::vector<VarBase*>& outputs,
+  void Trace(OpBase* op,
+             const std::map<std::string, std::vector<VarBase*>>& inputs,
+             const std::map<std::string, std::vector<VarBase*>>& outputs,
              framework::BlockDesc* block) {
-    framework::Scope* scope = GetScope(block);
+    // framework::Scope* scope = GetScope(block);
+    std::map<std::string, VarBase*> vars;
+
     framework::OpDesc* op_desc = op->op_desc_;
     VLOG(3) << "tracer tracing " << op_desc->Type();
     op_desc->InferShape(*block);
@@ -64,48 +75,60 @@ class Tracer {
     std::unique_ptr<framework::OperatorBase> op_base =
         framework::OpRegistry::CreateOp(*op_desc);
 
-    *op->input_vars_ = inputs;
-    for (VarBase* input : inputs) {
-      const std::string vname = input->var_desc_->Name();
-      framework::Variable* var = scope->Var(vname);
-      input->var_ = var;
-      if (!var->IsInitialized()) {
-        framework::VarDesc* var_desc = block->FindVar(vname);
-        if (var_desc->GetType() == framework::proto::VarType::LOD_TENSOR) {
-          var->GetMutable<framework::LoDTensor>();
+    framework::VariableValueMap invars_map;
+    framework::VariableValueMap outvars_map;
+
+    op->input_vars_ = inputs;
+    for (auto it : op->input_vars_) {
+      auto& invars = invars_map[it.first];
+      for (VarBase* inp : it.second) {
+        PADDLE_ENFORCE_NOT_NULL(inp->var_, "op %s input %s nullptr",
+                                op->op_desc_->Type(), inp->var_desc_->Name());
+
+        invars.push_back(inp->var_);
+        vars[inp->var_desc_->Name()] = inp;
+        if (inp->pre_op_) {
+          (*op->pre_ops_)[it.first].push_back(inp->pre_op_);
+          (*op->pre_ops_out_idx_)[it.first].push_back(inp->pre_op_out_idx_);
         } else {
-          LOG(ERROR) << "tracer doesn't support yet";
+          (*op->pre_ops_)[it.first].push_back(nullptr);
         }
+        VLOG(3) << "input vname " << inp->var_desc_->Name() << " "
+                << inp->var_->Get<framework::LoDTensor>().dims().size()
+                << reinterpret_cast<void*>(inp->var_);
       }
-      if (input->pre_op_) {
-        op->pre_ops_->push_back(input->pre_op_);
-        op->pre_ops_out_idx_->push_back(input->pre_op_out_idx_);
-      } else {
-        op->pre_ops_->push_back(nullptr);
-      }
-      VLOG(3) << "input vname " << vname << " "
-              << var->Get<framework::LoDTensor>().dims().size();
     }
 
-    *op->output_vars_ = outputs;
-    for (size_t i = 0; i < outputs.size(); ++i) {
-      const std::string vname = outputs[i]->var_desc_->Name();
-      framework::Variable* var = scope->Var(vname);
-      if (!var->IsInitialized()) {
-        framework::VarDesc* var_desc = block->FindVar(vname);
+    op->output_vars_ = outputs;
+    for (auto it : op->output_vars_) {
+      auto& outvars = outvars_map[it.first];
+      const std::vector<VarBase*>& outputs = it.second;
+      for (size_t i = 0; i < outputs.size(); ++i) {
+        VarBase* out = outputs[i];
+        outvars.push_back(out->var_);
+        vars[out->var_desc_->Name()] = out;
+
+        framework::VarDesc* var_desc = block->FindVar(out->var_desc_->Name());
         if (var_desc->GetType() == framework::proto::VarType::LOD_TENSOR) {
-          var->GetMutable<framework::LoDTensor>();
+          out->var_->GetMutable<framework::LoDTensor>();
         } else {
           LOG(ERROR) << "tracer doesn't support yet";
         }
+        out->pre_op_ = op;
+        out->pre_op_out_name_ = it.first;
+        out->pre_op_out_idx_ = i;
+
+        VLOG(3) << "output vname " << out->var_desc_->Name() << " "
+                << out->var_->Get<framework::LoDTensor>().dims().size() << " "
+                << reinterpret_cast<void*>(out->var_) << " "
+                << out->var_->IsInitialized();
       }
-      outputs[i]->var_ = var;
-      outputs[i]->pre_op_ = op;
-      outputs[i]->pre_op_out_idx_ = i;
     }
 
     VLOG(3) << "tracer running " << op_desc->Type();
-    op_base->Run(*scope, platform::CPUPlace());
+    framework::RuntimeContext ctx(invars_map, outvars_map);
+    op_base->Run(ctx, platform::CPUPlace());
+
     if (block == startup_block_) {
       op->grad_op_desc_ = nullptr;
       op->grad_to_var_ = nullptr;
@@ -115,6 +138,39 @@ class Tracer {
       CreateGradOp(*op_desc, {}, {block}, &grad_op_desc, grad_to_var);
       op->grad_op_desc_ = grad_op_desc;
       op->grad_to_var_ = grad_to_var;
+
+      for (auto it : grad_op_desc->Inputs()) {
+        auto& grad_in_vars = op->grad_input_vars_[it.first];
+        for (const std::string& grad_invar : it.second) {
+          block->FindRecursiveOrCreateVar(grad_invar);
+          auto var_it = op->grad_to_var_->find(grad_invar);
+          if (var_it == op->grad_to_var_->end()) {
+            auto fwd_var_it = vars.find(grad_invar);
+            PADDLE_ENFORCE(fwd_var_it != vars.end());
+            grad_in_vars.push_back(fwd_var_it->second->var_);
+          } else {
+            VarBase* var = vars[var_it->second];
+            if (!var->grads_->IsInitialized()) {
+              InitVar(var->var_, var->grads_);
+            }
+            grad_in_vars.push_back(var->grads_);
+          }
+        }
+      }
+      for (auto it : grad_op_desc->Outputs()) {
+        auto& grad_out_vars = op->grad_output_vars_[it.first];
+        for (const std::string& grad_outvar : it.second) {
+          block->FindRecursiveOrCreateVar(grad_outvar);
+          auto var_it = op->grad_to_var_->find(grad_outvar);
+          PADDLE_ENFORCE(var_it != op->grad_to_var_->end());
+          VarBase* var = vars[var_it->second];
+          if (!var->grads_->IsInitialized()) {
+            InitVar(var->var_, var->grads_);
+          }
+          LOG(ERROR) << grad_outvar << " map to " << var->var_desc_->Name();
+          grad_out_vars.push_back(var->grads_);
+        }
+      }
     }
     op->block_ = block;
   }

paddle/fluid/operators/fill_constant_op.cc

@@ -68,6 +68,41 @@ class FillConstantOp : public framework::OperatorBase {
     auto &dev_ctx = *pool.Get(dev_place);
     math::set_constant(dev_ctx, tensor, value);
   }
+
+  void RunImpl(const framework::RuntimeContext &ctx,
+               const platform::Place &dev_place) const override {
+    auto data_type =
+        static_cast<framework::proto::VarType::Type>(Attr<int>("dtype"));
+    auto value = Attr<float>("value");
+    auto force_cpu = Attr<bool>("force_cpu");
+
+    framework::Tensor *tensor = nullptr;
+
+    auto &out_var = *ctx.outputs.at("Out")[0];
+
+    if (out_var.IsType<framework::LoDTensor>()) {
+      tensor = out_var.GetMutable<framework::LoDTensor>();
+      tensor->Resize(framework::make_ddim(Attr<std::vector<int64_t>>("shape")));
+    } else if (out_var.IsType<framework::SelectedRows>()) {
+      tensor = out_var.GetMutable<framework::SelectedRows>()->mutable_value();
+      tensor->Resize(framework::make_ddim(Attr<std::vector<int64_t>>("shape")));
+    } else {
+      PADDLE_THROW(
+          "fill constant op's output only"
+          "supports SelectedRows and LoDTensor");
+    }
+
+    if (force_cpu) {
+      auto cpu = platform::CPUPlace();
+      tensor->mutable_data(cpu, data_type);
+    } else {
+      tensor->mutable_data(dev_place, data_type);
+    }
+
+    platform::DeviceContextPool &pool = platform::DeviceContextPool::Instance();
+    auto &dev_ctx = *pool.Get(dev_place);
+    math::set_constant(dev_ctx, tensor, value);
+  }
 };
 
 class FillConstantOpVarTypeInference : public framework::VarTypeInference {

paddle/fluid/pybind/pybind.cc

@@ -124,9 +124,7 @@ PYBIND11_MODULE(core, m) {
   py::class_<imperative::VarBase, PyVarBase>(m, "VarBase", R"DOC()DOC")
       .def(py::init<>())
       .def("_run_backward",
-           [](imperative::VarBase &self, framework::Scope *scope) {
-             self.RunBackward(scope);
-           })
+           [](imperative::VarBase &self) { self.RunBackward(); })
       .def("_grad", &imperative::VarBase::Grad)
       .def_property(
           "desc",
@@ -134,7 +132,13 @@ PYBIND11_MODULE(core, m) {
           [](imperative::VarBase &self, framework::VarDesc *var_desc) {
             self.var_desc_ = var_desc;
           },
-          py::return_value_policy::reference);
+          py::return_value_policy::reference)
+      .def_property("var",
+                    [](const imperative::VarBase &self) { return self.var_; },
+                    [](imperative::VarBase &self, framework::Variable *var) {
+                      self.var_ = var;
+                    },
+                    py::return_value_policy::reference);
 
   py::class_<imperative::OpBase, PyOpBase>(m, "OpBase", R"DOC()DOC")
       .def(py::init<>())

python/paddle/fluid/framework.py

@@ -15,6 +15,7 @@
 from __future__ import print_function
 
 import collections
+from collections import defaultdict
 import contextlib
 import os
 import re
@@ -369,13 +370,11 @@ class Variable(object):
             self._ivar.desc = self.desc
 
     def _numpy(self):
-        scope = _imperative_tracer().get_scope(self.block.desc)
-        tensor = core.get_variable_tensor(scope, self.desc.name())
+        tensor = self._ivar.var.get_tensor()
         return np.array(tensor)
 
     def _backward(self):
-        scope = _imperative_tracer().get_scope(self.block.desc)
-        self._ivar._run_backward(scope)
+        self._ivar._run_backward()
 
     def _gradient(self):
         return np.array(self._ivar._grad())
@@ -692,20 +691,20 @@ class Operator(object):
         if _in_imperative_mode():
             self.iop = core.OpBase()
             self.iop.desc = self.desc
-            self.inputs = []
+            self.inputs = defaultdict(list)
             if inputs is not None:
-                for inp in inputs.values():
-                    if isinstance(inp, Variable):
-                        self.inputs.append(inp)
-                    elif isinstance(inp, list) or isinstance(inp, tuple):
-                        self.inputs.extend(inp[:])
-            self.outputs = []
+                for k, v in six.iteritems(inputs):
+                    if isinstance(v, Variable):
+                        self.inputs[k].append(v._ivar)
+                    elif isinstance(v, list) or isinstance(v, tuple):
+                        self.inputs[k].extend([var._ivar for var in v])
+            self.outputs = defaultdict(list)
             if outputs is not None:
-                for out in outputs.values():
-                    if isinstance(out, Variable):
-                        self.outputs.append(out)
-                    elif isinstance(out, list) or isinstance(out, tuple):
-                        self.outputs.extend(out[:])
+                for k, v in six.iteritems(outputs):
+                    if isinstance(v, Variable):
+                        self.outputs[k].append(v._ivar)
+                    elif isinstance(v, list) or isinstance(v, tuple):
+                        self.outputs[k].extend([var._ivar for var in v])
 
     def _has_kernel(self, op_type):
         return op_type not in self.OP_WITHOUT_KERNEL_SET
@@ -1273,8 +1272,7 @@ class Block(object):
         op_desc = self.desc.append_op()
         op = Operator(block=self, desc=op_desc, *args, **kwargs)
         if _in_imperative_mode():
-            _imperative_tracer().trace(op.iop, [v._ivar for v in op.inputs],
-                                       [v._ivar for v in op.outputs], self.desc)
+            _imperative_tracer().trace(op.iop, op.inputs, op.outputs, self.desc)
         self.ops.append(op)
         return op
 
@@ -1325,8 +1323,7 @@ class Block(object):
         op_desc = self.desc._prepend_op()
         op = Operator(self, op_desc, *args, **kwargs)
         if _in_imperative_mode():
-            _imperative_tracer().trace(op.iop, [v._ivar for v in op.inputs],
-                                       [v._ivar for v in op.outputs], self.desc)
+            _imperative_tracer().trace(op.iop, op.inputs, op.outputs, self.desc)
         self.ops.insert(0, op)
         return op
 

python/paddle/fluid/imperative/base.py

@@ -46,8 +46,7 @@ def to_variable(value, block=None):
             name=None,
             shape=value.shape,
             dtype=value.dtype)
-        scope = framework._imperative_tracer().get_scope(block.desc)
-        var = scope.var(py_var.name)
+        var = py_var._ivar.var
         tensor = var.get_tensor()
         tensor.set(value, core.CPUPlace())
         return py_var

python/paddle/fluid/layer_helper.py

@@ -20,7 +20,7 @@ import six
 import sys
 import numpy as np
 
-from .framework import Variable, Parameter, default_main_program, default_startup_program, dtype_is_floating
+from .framework import Variable, Parameter, default_main_program, default_startup_program, dtype_is_floating, _in_imperative_mode
 from . import unique_name
 from paddle.fluid.initializer import Constant, Xavier
 from paddle.fluid.imperative import base
@@ -313,11 +313,20 @@ class LayerHelper(object):
             param = self._create_weight_normalize(attr, shape, dtype)
             WeightNormParamAttr.params_with_weight_norm.append(param)
             return param
-
-        self.startup_program.global_block().create_parameter(
-            dtype=dtype, shape=shape, **attr._to_kwargs(with_initializer=True))
-        return self.main_program.global_block().create_parameter(
-            dtype=dtype, shape=shape, **attr._to_kwargs())
+        if _in_imperative_mode():
+            self.main_program.global_block().create_parameter(
+                dtype=dtype, shape=shape, **attr._to_kwargs())
+            return self.startup_program.global_block().create_parameter(
+                dtype=dtype,
+                shape=shape,
+                **attr._to_kwargs(with_initializer=True))
+        else:
+            self.startup_program.global_block().create_parameter(
+                dtype=dtype,
+                shape=shape,
+                **attr._to_kwargs(with_initializer=True))
+            return self.main_program.global_block().create_parameter(
+                dtype=dtype, shape=shape, **attr._to_kwargs())
 
     def get_parameter(self, name):
         param = self.main_program.global_block().var(name)

python/paddle/fluid/layers/nn.py

@@ -20,6 +20,7 @@ from __future__ import print_function
 import numpy as np
 import six
 import os
+import sys
 import inspect
 from ..layer_helper import LayerHelper
 from ..initializer import Normal, Constant
@@ -9682,6 +9683,7 @@ class FC(layers.PyLayer):
             shape=param_shape,
             dtype=self._dtype,
             is_bias=False)
+        sys.stderr.write('created w: %s\n' % self._w.name)
 
     def forward(self, inputs):
         tmp = self._helper.create_variable_for_type_inference(self._dtype)

python/paddle/fluid/tests/unittests/test_imperative.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import sys
 import contextlib
 import unittest
 import numpy as np
@@ -38,7 +39,9 @@ class MyLayer(fluid.imperative.PyLayer):
     def forward(self, inputs):
         x = fluid.layers.relu(inputs[0])
         self._x_for_debug = x
-        return [fluid.layers.elementwise_mul(x, x)]
+        x = fluid.layers.elementwise_mul(x, x)
+        x = fluid.layers.reduce_sum(x)
+        return [x]
 
 
 class MLP(fluid.imperative.PyLayer):
@@ -79,10 +82,12 @@ class TestImperative(unittest.TestCase):
         with new_program_scope():
             inp = fluid.layers.data(
                 name="inp", shape=[3], append_batch_size=False)
-            l = MyLayer()
-            x = l(inp)[0]
+            x = fluid.layers.relu(inp)
+            x_for_debug = x
+            x = fluid.layers.elementwise_mul(x, x)
+            x = fluid.layers.reduce_sum(x)
             param_grads = fluid.backward.append_backward(
-                x, parameter_list=[l._x_for_debug.name])[0]
+                x, parameter_list=[x_for_debug.name])[0]
             exe = fluid.Executor(fluid.CPUPlace())
 
             static_out, static_grad = exe.run(