AddBiasOp does not care num_flatten_dims (#5200)

* AddBiasOp does not care num_flatten_dims * Add comments

Author: reyoung

python/paddle/v2/framework/layer_helper.py

@@ -142,8 +142,24 @@ def create_global_variable(self, *args, **kwargs):
  return self.program.global_block().create_var(
  *args, persistable=False, **kwargs)
 
- def append_bias_op(self, input_var):
- size = list(input_var.shape[1:])
+ def append_bias_op(self, input_var, num_flatten_dims=None):
+ """
+ Append bias operator and return its output. If the user does not set 
+ bias_attr, append_bias_op will return input_var
+ 
+ :param input_var: the input variable. The len(input_var.shape) is larger
+ or equal than 2.
+ :param num_flatten_dims: The input tensor will be flatten as a matrix 
+ when adding bias.
+ `matrix.shape = product(input_var.shape[0:num_flatten_dims]), product(
+ input_var.shape[num_flatten_dims:])`
+ """
+ if num_flatten_dims is None:
+ num_flatten_dims = self.kwargs.get('num_flatten_dims', None)
+ if num_flatten_dims is None:
+ num_flatten_dims = 1
+
+ size = list(input_var.shape[num_flatten_dims:])
  bias_attr = self.bias_attr()
  if not bias_attr:
  return input_var