update

paddle/pybind/protobuf.cc

@@ -243,6 +243,7 @@ void BindOpDesc(py::module &m) {
       .def("set_input", &OpDescBind::SetInput)
       .def("output", &OpDescBind::Output)
       .def("output_names", &OpDescBind::OutputNames)
+      .def("output_arg_names", &OpDescBind::OutputArgumentNames)
       .def("set_output", &OpDescBind::SetOutput)
       .def("has_attr", &OpDescBind::HasAttr)
       .def("attr_type", &OpDescBind::GetAttrType)

paddle/pybind/pybind.cc

@@ -282,7 +282,7 @@ All parameter, weight, gradient are variables in Paddle.
     }
     return ret_values;
   });
-  m.def("get_grad_op_descs",
+  m.def("get_grad_op_desc",
         [](const OpDescBind &op_desc,
            const std::unordered_set<std::string> &no_grad_set,
            std::unordered_map<std::string, std::string> &grad_to_var,

python/paddle/v2/fluid/backward.py

 from paddle.v2.fluid import framework as framework
 from . import core
+import collections
 
 __all__ = ['append_backward_ops']
 
@@ -20,6 +21,20 @@ def backward_impl(block, target_block, no_grad_set, grad_to_var, callback):
                                              no_grad_set[block.idx],
                                              grad_to_var, grad_sub_block_list)
         grad_op_descs.append(grad_op_desc)
+    # grad_op_descs = [[op1_g1, op1_g2], [op2_g], ...]
+    # flatten grad_op_descs
+    grad_op_descs = [op for sublist in grad_op_descs for op in sublist]  # ?????
+
+    output_vars = collections.defaultdict(list)
+    for pos, op_desc in enumerate(grad_op_descs):
+        for var_name in op_desc.output_arg_names():
+            output_vars[var_name].append(pos)
+    for var_name, poses in output_vars.iteritems():
+        if len(poses) == 1:
+            continue
+        renamed_list = []
+        for pos in reversed(sorted(poses)):
+            new_name = var_name + "@RENAMED@" + len(renamed_list)
 
 
 def append_backward_ops(loss, parameter_list=None, no_grad_set=None):