TensorFlow 池化层

在 TensorFlow 中使用池化层

在下面的练习中，你需要设定池化层的大小，strides，以及相应的 padding。你可以参考 tf.nn.max_pool()。Padding 与卷积 padding 的原理一样。

说明

完成 maxpool 函数中所有的 TODO。
设定 strides，padding 和 ksize 使得池化的结果维度为 (1, 2, 2, 1)。

Start Quiz:

"""
Set the values to `strides` and `ksize` such that
the output shape after pooling is (1, 2, 2, 1).
"""
import tensorflow as tf
import numpy as np

# `tf.nn.max_pool` requires the input be 4D (batch_size, height, width, depth)
# (1, 4, 4, 1)
x = np.array([
    [0, 1, 0.5, 10],
    [2, 2.5, 1, -8],
    [4, 0, 5, 6],
    [15, 1, 2, 3]], dtype=np.float32).reshape((1, 4, 4, 1))
X = tf.constant(x)

def maxpool(input):
    # TODO: Set the ksize (filter size) for each dimension (batch_size, height, width, depth)
    ksize = [?, ?, ?, ?]
    # TODO: Set the stride for each dimension (batch_size, height, width, depth)
    strides = [?, ?, ?, ?]
    # TODO: set the padding, either 'VALID' or 'SAME'.
    padding = ?
    # https://www.tensorflow.org/versions/r0.11/api_docs/python/nn.html#max_pool
    return tf.nn.max_pool(input, ksize, strides, padding)
    
out = maxpool(X)

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