From ae31faaa877ef2c697123add87136b27a8d1410a Mon Sep 17 00:00:00 2001
From: chengduo <30176695+chengduoZH@users.noreply.github.com>
Date: Fri, 20 Sep 2019 16:39:12 +0800
Subject: [PATCH] refine optimier function (#19886)

test=developt
---
 python/paddle/fluid/optimizer.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/python/paddle/fluid/optimizer.py b/python/paddle/fluid/optimizer.py
index f7db8ce32b..e33f5c13be 100644
--- a/python/paddle/fluid/optimizer.py
+++ b/python/paddle/fluid/optimizer.py
@@ -491,6 +491,10 @@ class Optimizer(object):
             else:
                 assert (isinstance(callbacks, list))
             program = loss.block.program
+            assert len(loss.shape) == 1 and loss.shape[0] == 1, \
+                "The loss.shape should be (1L,), but the current loss.shape is {}. " \
+                "Maybe that you should call fluid.layers.mean to process the current loss.".format(
+                    loss.shape)
             with program_guard(program, startup_program):
                 params_grads = append_backward(loss, parameter_list,
                                                no_grad_set, callbacks)
-- 
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