open test_word2vec (#6104)

Author: QiJune

python/paddle/v2/fluid/tests/book/test_word2vec.py

@@ -58,10 +58,6 @@
 place = fluid.CPUPlace()
 exe = fluid.Executor(place)
 
-# fix https://github.com/PaddlePaddle/Paddle/issues/5434 then remove
-# below exit line.
-exit(0)
-
 exe.run(fluid.default_startup_program())
 
 for pass_id in range(PASS_NUM):
@@ -79,6 +75,6 @@
                                   'nextw': input_data[4]
                               },
                               fetch_list=[avg_cost])
-        if avg_cost_np[0] < 10.0:
+        if avg_cost_np[0] < 5.0:
             exit(0)  # if avg cost less than 10.0, we think our code is good.
 exit(1)