Add reorder flag for DynamicRNN's memory function.

Author: pkuyym

python/paddle/v2/fluid/layers/control_flow.py

@@ -1310,20 +1310,44 @@ def __call__(self, *args, **kwargs):
         else:
             return self.outputs
 
-    def memory(self, init=None, shape=None, value=0.0, dtype='float32'):
+    def memory(self,
+               init=None,
+               shape=None,
+               value=0.0,
+               need_reorder=False,
+               dtype='float32'):
         self._assert_in_rnn_block_('memory')
         if init is not None:
             if not isinstance(init, Variable):
                 raise TypeError(
                     "The input arg `init` of memory() must be a Variable")
             parent_block = self._parent_block_()
+            init_tensor = init
+            if need_reorder == True:
+                if self.lod_rank_table is None:
+                    raise ValueError(
+                        'If set need_reorder to True, make sure step_input be '
+                        'invoked before '
+                        'memory(init=init, need_reordered=True, ...).')
+                init_reordered = parent_block.create_var(
+                    name=unique_name('dynamic_rnn_mem_init_reordered'),
+                    type=core.VarDesc.VarType.LOD_TENSOR,
+                    dtype=init.dtype)
+                parent_block.append_op(
+                    type='reorder_lod_tensor_by_rank',
+                    inputs={
+                        'X': [init_tensor],
+                        'RankTable': [self.lod_rank_table]
+                    },
+                    outputs={'Out': [init_reordered]})
+                init_tensor = init_reordered
             mem_array = parent_block.create_var(
                 name=unique_name('dynamic_rnn_mem_array'),
                 type=core.VarDesc.VarType.LOD_TENSOR_ARRAY,
                 dtype=init.dtype)
             parent_block.append_op(
                 type='write_to_array',
-                inputs={'X': init,
+                inputs={'X': init_tensor,
                         'I': self.zero_idx},
                 outputs={'Out': mem_array})
             retv = array_read(array=mem_array, i=self.step_idx)