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  • tensorflow函数解析:Session.run和Tensor.eval

    原问题链接:

    http://stackoverflow.com/questions/33610685/in-tensorflow-what-is-the-difference-between-session-run-and-tensor-eval

    译:

    问题:

    tensorflow有两种方式:Session.run和 Tensor.eval,这两者的区别在哪?

    答:

    如果你有一个Tensor t,在使用t.eval()时,等价于:tf.get_default_session().run(t).

    举例:

    t = tf.constant(42.0)
    sess = tf.Session()
    with sess.as_default():   # or `with sess:` to close on exit
        assert sess is tf.get_default_session()
        assert t.eval() == sess.run(t)

    这其中最主要的区别就在于你可以使用sess.run()在同一步获取多个tensor中的值,

    例如:

    t = tf.constant(42.0)
    u = tf.constant(37.0)
    tu = tf.mul(t, u)
    ut = tf.mul(u, t)
    with sess.as_default():
       tu.eval()  # runs one step
       ut.eval()  # runs one step
       sess.run([tu, ut])  # evaluates both tensors in a single step

    注意到:每次使用 evalrun时,都会执行整个计算图,为了获取计算的结果,将它分配给tf.Variable,然后获取。

    原文如下:

    Question:

    TensorFlow has two ways to evaluate part of graph: Session.run on a list of variables and Tensor.eval. Is there a difference between these two?

    Answer:

    If you have a Tensor t, calling t.eval() is equivalent to calling tf.get_default_session().run(t).

    You can make a session the default as follows:

    t = tf.constant(42.0)
    sess = tf.Session()
    with sess.as_default():   # or `with sess:` to close on exit
        assert sess is tf.get_default_session()
        assert t.eval() == sess.run(t)

    The most important difference is that you can use sess.run() to fetch the values of many tensors in the same step:

    t = tf.constant(42.0)
    u = tf.constant(37.0)
    tu = tf.mul(t, u)
    ut = tf.mul(u, t)
    with sess.as_default():
       tu.eval()  # runs one step
       ut.eval()  # runs one step
       sess.run([tu, ut])  # evaluates both tensors in a single step

    Note that each call to eval and run will execute the whole graph from scratch. To cache the result of a computation, assign it to a tf.Variable.

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  • 原文地址:https://www.cnblogs.com/antflow/p/7234192.html
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