What is tf.nn.max_pool's ksize parameter used for?
<p>In the definition of <code>tf.nn.max_pool</code>, what is <code>ksize</code> used for?</p>

<pre><code>tf.nn.max_pool(value, ksize, strides, padding, data_format='NHWC', name=None)

Performs the max pooling on the input.

Args:

value: A 4-D Tensor with shape [batch, height, width, channels] and type    tf.float32.
ksize: A list of ints that has length &gt;= 4. The size of the window for each dimension of the input tensor.
</code></pre>

<p>For instance, if an <code>input value</code> is of <code>tensor :  [1, 64, 64, 3]</code> and <code>ksize=3</code>.what does that mean?</p>