问题描述
Session.run(fetches, feed_dict) 是否保证按顺序执行其 fetches 参数?
Is Session.run(fetches, feed_dict) guaranteed to execute its fetches arguments in-order?
文档似乎没有提到它.
例如，如果您运行
sess.run([accuracy, train_op], feed_dict=feed_dict)
执行顺序很重要:train_op会更新影响accuracy的参数.
the order of execution matters: train_op will update parameters affecting accuracy.
推荐答案
没有.默认情况下，Tensorflow 可以以任何顺序自由评估运算符.由于并发，该顺序甚至可能在运行之间发生变化.这通常是一件好事，因为这意味着 Tensorflow 可以优化使用可用硬件.如果您的代码改变了诸如变量之类的状态，则可能会出现问题.
No. By default, Tensorflow is free to evaluate operators in any order. Because of concurrency, that order may even change between runs. This is usually a good thing because it means that Tensorflow may make optimal use of the available hardware. It can be problematic if your code mutates state such as Variables.
但是，如果出于某种原因您确实希望控制求值顺序，通常您可以使用控制依赖来强制操作符之间的顺序.此处记录了控制依赖项:
However, if for some reason you do wish to control the order of evaluation, in general you can use control dependencies to enforce an order between operators. Control dependencies are documented here:
https://www.tensorflow.org/api_docs/python/tf/图#control_dependencies
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