Add block.fwd_block_id

paddle/fluid/framework/block_desc.cc

@@ -46,11 +46,25 @@ VarDesc *BlockDesc::FindVarRecursive(const std::string &name) const {
   if (name == kEmptyVarName) return nullptr;
 
   auto it = vars_.find(name);
-  if (it == vars_.end()) {
-    return Parent() == kNoneBlockIndex ? nullptr
-                                       : ParentBlock()->FindVarRecursive(name);
+  if (it != vars_.end()) {
+    return it->second.get();
   }
-  return it->second.get();
+
+  BlockDesc *tmp = ParentBlock();
+
+  if (tmp != nullptr) {
+    auto ptr = tmp->FindVarRecursive(name);
+    if (ptr != nullptr) {
+      return ptr;
+    }
+  }
+
+  tmp = ForwardBlock();
+  if (tmp != nullptr) {
+    return tmp->FindVarRecursive(name);
+  }
+
+  return nullptr;
 }
 
 VarDesc &BlockDesc::FindRecursiveOrCreateVar(const std::string &name_bytes) {
@@ -136,10 +150,7 @@ void BlockDesc::Flush() {
 }
 
 BlockDesc *BlockDesc::ParentBlock() const {
-  if (this->desc_->parent_idx() == kNoneBlockIndex) {
-    return nullptr;
-  }
-  return prog_->MutableBlock(static_cast<size_t>(this->desc_->parent_idx()));
+  return prog_->MutableBlock(static_cast<size_t>(desc_->parent_idx()));
 }
 
 proto::BlockDesc *BlockDesc::Proto() {
@@ -186,5 +197,16 @@ void BlockDesc::ClearPBVars() {
   }
 }
 
+void BlockDesc::SetForwardBlockID(int32_t forward_block_id) {
+  PADDLE_ENFORCE(!desc_->has_forward_block_idx(),
+                 "Parent block ID has been set to %d. Cannot set to %d",
+                 desc_->forward_block_idx(), forward_block_id);
+  desc_->set_forward_block_idx(forward_block_id);
+}
+
+BlockDesc *BlockDesc::ForwardBlock() const {
+  return prog_->MutableBlock(static_cast<size_t>(desc_->forward_block_idx()));
+}
+
 }  // namespace framework
 }  // namespace paddle

paddle/fluid/framework/block_desc.h

@@ -49,6 +49,8 @@ class BlockDesc {
 
   int32_t Parent() const { return desc_->parent_idx(); }
 
+  int32_t ForwardBlockID() const { return desc_->forward_block_idx(); }
+
   VarDesc *Var(const std::string &name_bytes);
 
   VarDesc *FindVar(const std::string &name_bytes) const;
@@ -73,6 +75,10 @@ class BlockDesc {
 
   BlockDesc *ParentBlock() const;
 
+  BlockDesc *ForwardBlock() const;
+
+  void SetForwardBlockID(int32_t forward_block_id);
+
   OpDesc *AppendOp();
 
   void AppendAllocatedOp(std::unique_ptr<OpDesc> &&op_desc);
@@ -91,7 +97,7 @@ class BlockDesc {
 
   proto::BlockDesc *Proto();
 
-  ProgramDesc *Program() { return this->prog_; }
+  ProgramDesc *Program() const { return this->prog_; }
 
  private:
   void ClearPBOps();

paddle/fluid/framework/framework.proto

@@ -158,6 +158,7 @@ message BlockDesc {
   required int32 parent_idx = 2;
   repeated VarDesc vars = 3;
   repeated OpDesc ops = 4;
+  optional int32 forward_block_idx = 5 [ default = -1 ];
 }
 
 // Please refer to

paddle/fluid/framework/program_desc.h

@@ -38,7 +38,13 @@ class ProgramDesc {
 
   BlockDesc *AppendBlock(const BlockDesc &parent);
 
-  BlockDesc *MutableBlock(size_t idx) { return blocks_[idx].get(); }
+  BlockDesc *MutableBlock(size_t idx) {
+    if (idx == static_cast<size_t>(kNoneBlockIndex)) {
+      return nullptr;
+    } else {
+      return blocks_[idx].get();
+    }
+  }
 
   const BlockDesc &Block(size_t idx) const { return *blocks_[idx]; }
 

paddle/fluid/operators/while_op.cc

@@ -231,7 +231,8 @@ class WhileGradOpDescMaker : public framework::SingleGradOpDescMaker {
     while_grad->SetInput(kStepScopes, Output(kStepScopes));
 
     auto *grad_block = this->grad_block_[0];
-    auto *fwd_block = grad_block->ParentBlock();
+    auto *fwd_block = grad_block->ForwardBlock();
+    auto *parent_block = grad_block->ParentBlock();
 
     // Not all of IGs will be generated by inner gradient operators of while op.
     // Ignore IGs that is not generated by the inside block.
@@ -265,8 +266,10 @@ class WhileGradOpDescMaker : public framework::SingleGradOpDescMaker {
       for (auto &input_name : op->InputArgumentNames()) {
         // If the input of Op has been recorded or is generated by the forward
         // block, do not make it as input again.
+
         if (block_ins.find(input_name) != block_ins.end() ||
-            fwd_block->FindVar(input_name) != nullptr) {
+            fwd_block->FindVar(input_name) != nullptr ||
+            parent_block->FindVar(input_name) != nullptr) {
           continue;
         }
         extra_inputs.insert(input_name);

paddle/fluid/pybind/protobuf.cc

@@ -155,6 +155,8 @@ void BindBlockDesc(py::module &m) {
   py::class_<BlockDesc>(m, "BlockDesc", "")
       .def_property_readonly("id", &BlockDesc::ID)
       .def_property_readonly("parent", &BlockDesc::Parent)
+      .def("get_forward_block_idx", &BlockDesc::ForwardBlockID)
+      .def("set_forward_block_idx", &BlockDesc::SetForwardBlockID)
       .def("append_op", &BlockDesc::AppendOp,
            py::return_value_policy::reference)
       .def("prepend_op", &BlockDesc::PrependOp,

python/paddle/v2/fluid/backward.py

@@ -298,7 +298,8 @@ def _append_backward_ops_(block,
         # If the op has its own sub-block, deal with the sub-block first
         if op.has_attr("sub_block"):
             sub_block = program.block(op.block_attr("sub_block"))
-            grad_sub_block = program.create_block(parent_idx=sub_block.idx)
+            grad_sub_block = program.create_block()
+            grad_sub_block.set_forward_block_idx(sub_block.idx)
             cb = _callback_lookup_(op)
             if cb is not None:
                 if callbacks is None:
@@ -310,6 +311,8 @@ def _append_backward_ops_(block,
             else:
                 _append_backward_ops_(sub_block, sub_block.ops, grad_sub_block,
                                       no_grad_dict, grad_to_var, callbacks)
+
+            program.rollback()
             grad_sub_block_list.append(grad_sub_block.desc)
 
         # Getting op's corresponding grad_op

python/paddle/v2/fluid/framework.py

@@ -678,6 +678,13 @@ class Block(object):
     def parent_idx(self):
         return self.desc.parent
 
+    @property
+    def forward_block_idx(self):
+        return self.desc.get_forward_block_idx()
+
+    def set_forward_block_idx(self, idx):
+        self.desc.set_forward_block_idx(idx)
+
     @property
     def idx(self):
         return self.desc.id
@@ -695,11 +702,22 @@ class Block(object):
             return self.var(name)
         else:
             if self.idx == 0:
-                raise ValueError("var %s is not in block(%d) nor its parents." %
-                                 name, self.idx)
+                raise ValueError(
+                    "var {0} is not in block({1}) nor its parents.".format(
+                        name, self.idx))
             else:
-                parent_block = self.program.block(self.parent_idx)
-                return parent_block.var_recursive(name)
+                # DFS
+                try:
+                    parent_block = self.program.block(self.parent_idx)
+                    return parent_block.var_recursive(name)
+                except ValueError:
+                    fwd_block = self.program.block(
+                        self.forward_block_idx
+                    ) if self.forward_block_idx != -1 else None
+                    if fwd_block is not None:
+                        return fwd_block.var_recursive(name)
+                    else:
+                        raise
 
     def all_parameters(self):
         return list(self.iter_parameters())