tensorflow的程式中,在main函式下,都是使用tf.app.run()來啟動

檢視原始碼可知,該函式是用來處理flag解析，然後執行main函式，那麼flag解析是什麼意思呢？諸如這樣的：

# tensorflow/tensorflow/python/platform/default/_app.py
 
# Copyright 2015 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
 
"""Generic entry point script."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
 
import sys
 
from tensorflow.python.platform import flags
 
 
def run(main=None):
  f = flags.FLAGS
  f._parse_flags()
  main = main or sys.modules['__main__'].main
  sys.exit(main(sys.argv))
 

處理flag解析，然後執行main函式，那麼flag解析是什麼意思呢？諸如這樣的：

tf.app.flags.DEFINE_boolean("self_test", False, "True if running a self test.")
tf.app.flags.DEFINE_boolean('use_fp16', False,
                            "Use half floats instead of full floats if True.")
FLAGS = tf.app.flags.FLAGS

那麼 tf.app.run()什麼意思呢 ？ 
應該是函式入口，類似於c/c++中的main()

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大概意思是通過處理flag解析，然後執行main函式。

說白了，有兩種情況：

如果你的程式碼中的入口函式不叫main()，而是一個其他名字的函式，如test()，則你應該這樣寫入口tf.app.run(test())
如果你的程式碼中的入口函式叫main()，則你就可以把入口寫成tf.app.run()
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參考源：

How does tf.app.run() work?

tf.app.run()