diff --git a/python/paddle/fluid/transpiler/memory_optimization_transpiler.py b/python/paddle/fluid/transpiler/memory_optimization_transpiler.py
index ac57a8b4ef936163b31b969bc7e92d4167dbbb9c..76adedfadbd7ee2c13fc108522627f1210ffec79 100755
--- a/python/paddle/fluid/transpiler/memory_optimization_transpiler.py
+++ b/python/paddle/fluid/transpiler/memory_optimization_transpiler.py
@@ -47,7 +47,6 @@ PRINT_LOG = False
 class ControlFlowGraph(object):
     def __init__(self, program, ops, forward_num, skip_opt):
         self._program = program
-        self._dup_program = program.clone()
         self._ops = ops
         self._forward_num = forward_num
         self._successors = defaultdict(set)
@@ -230,8 +229,6 @@ class ControlFlowGraph(object):
                     for x in defs_can_optimize
                 ]
                 for x, x_shape in out_pair:
-                    if (x, x_shape) in self.pool:
-                        raise ValueError("x in pool, %s, %s" % (x, x_shape))
                     # If x is both in uses and defs, it can not be optimized!
                     if x in self._uses[i]:
                         continue
@@ -239,14 +236,15 @@ class ControlFlowGraph(object):
                         cache_var = cache_pair[0]
                         cache_shape = cache_pair[1]
                         if not self._has_var(block_desc, cache_var, is_forward):
-                            raise ValueError("cache",
-                                             cpt.to_text(cache_var),
-                                             " Not exists!")
+                            if PRINT_LOG:
+                                print("cache %s not exists!" %
+                                      (cpt.to_text(cache_var)))
+                            continue
                         if x == cache_var:
-                            raise ValueError("x : ",
-                                             cpt.to_text(x), " cache : ",
-                                             cpt.to_text(cache_var),
-                                             " is same var!")
+                            if PRINT_LOG:
+                                print("x : ", cpt.to_text(x), " cache : ",
+                                      cpt.to_text(cache_var), " is same var!")
+                            break
 
                         x_dtype = self._find_var(block_desc, x,
                                                  is_forward).dtype()
@@ -383,10 +381,13 @@ def memory_optimize(input_program, skip_opt_set=None, print_log=False, level=0):
 
       Note: it doesn't not support subblock nested in subblock.
 
-    :param input_program(str): Input Program
-    :param print_log: whether to print debug log.
-    :param level: If level=0, reuse if the shape is completely equal, o
-    :return:
+    Args:
+        input_program(str): Input Program
+        skip_opt_set(set): vars wil be skipped in memory optimze
+        print_log(bool): whether to print debug log.
+        level(int): If level=0, reuse if the shape is completely equal, o
+    Returns:
+        None
     """
     if level != 0 and level != 1:
         raise ValueError("only support opt_level 0 or 1.")
@@ -407,6 +408,9 @@ def release_memory(input_program, skip_opt_set=None):
 
     Args:
         input_program(Program): The program will be inserted :code:`delete_op`.
+        skip_opt_set(set): vars wil be skipped in memory optimze
+    Returns:
+        None
     """
     cfgs = _get_cfgs(input_program)
     for cfg in cfgs: