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dS )	zMax pooling 2D layer.é    N)Ú	Pooling2D)Úkeras_exportzkeras.layers.MaxPool2Dzkeras.layers.MaxPooling2Dc                       s"   e Zd ZdZd‡ fdd„	Z‡  ZS )ÚMaxPooling2Da  Max pooling operation for 2D spatial data.

    Downsamples the input along its spatial dimensions (height and width)
    by taking the maximum value over an input window
    (of size defined by `pool_size`) for each channel of the input.
    The window is shifted by `strides` along each dimension.

    The resulting output,
    when using the `"valid"` padding option, has a spatial shape
    (number of rows or columns) of:
    `output_shape = math.floor((input_shape - pool_size) / strides) + 1`
    (when `input_shape >= pool_size`)

    The resulting output shape when using the `"same"` padding option is:
    `output_shape = math.floor((input_shape - 1) / strides) + 1`

    For example, for `strides=(1, 1)` and `padding="valid"`:

    >>> x = tf.constant([[1., 2., 3.],
    ...                  [4., 5., 6.],
    ...                  [7., 8., 9.]])
    >>> x = tf.reshape(x, [1, 3, 3, 1])
    >>> max_pool_2d = tf.keras.layers.MaxPooling2D(pool_size=(2, 2),
    ...    strides=(1, 1), padding='valid')
    >>> max_pool_2d(x)
    <tf.Tensor: shape=(1, 2, 2, 1), dtype=float32, numpy=
      array([[[[5.],
               [6.]],
              [[8.],
               [9.]]]], dtype=float32)>

    For example, for `strides=(2, 2)` and `padding="valid"`:

    >>> x = tf.constant([[1., 2., 3., 4.],
    ...                  [5., 6., 7., 8.],
    ...                  [9., 10., 11., 12.]])
    >>> x = tf.reshape(x, [1, 3, 4, 1])
    >>> max_pool_2d = tf.keras.layers.MaxPooling2D(pool_size=(2, 2),
    ...    strides=(2, 2), padding='valid')
    >>> max_pool_2d(x)
    <tf.Tensor: shape=(1, 1, 2, 1), dtype=float32, numpy=
      array([[[[6.],
               [8.]]]], dtype=float32)>

    Usage Example:

    >>> input_image = tf.constant([[[[1.], [1.], [2.], [4.]],
    ...                            [[2.], [2.], [3.], [2.]],
    ...                            [[4.], [1.], [1.], [1.]],
    ...                            [[2.], [2.], [1.], [4.]]]])
    >>> output = tf.constant([[[[1], [0]],
    ...                       [[0], [1]]]])
    >>> model = tf.keras.models.Sequential()
    >>> model.add(tf.keras.layers.MaxPooling2D(pool_size=(2, 2),
    ...    input_shape=(4, 4, 1)))
    >>> model.compile('adam', 'mean_squared_error')
    >>> model.predict(input_image, steps=1)
    array([[[[2.],
             [4.]],
            [[4.],
             [4.]]]], dtype=float32)

    For example, for stride=(1, 1) and padding="same":

    >>> x = tf.constant([[1., 2., 3.],
    ...                  [4., 5., 6.],
    ...                  [7., 8., 9.]])
    >>> x = tf.reshape(x, [1, 3, 3, 1])
    >>> max_pool_2d = tf.keras.layers.MaxPooling2D(pool_size=(2, 2),
    ...    strides=(1, 1), padding='same')
    >>> max_pool_2d(x)
    <tf.Tensor: shape=(1, 3, 3, 1), dtype=float32, numpy=
      array([[[[5.],
               [6.],
               [6.]],
              [[8.],
               [9.],
               [9.]],
              [[8.],
               [9.],
               [9.]]]], dtype=float32)>

    Args:
      pool_size: integer or tuple of 2 integers,
        window size over which to take the maximum.
        `(2, 2)` will take the max value over a 2x2 pooling window.
        If only one integer is specified, the same window length
        will be used for both dimensions.
      strides: Integer, tuple of 2 integers, or None.
        Strides values.  Specifies how far the pooling window moves
        for each pooling step. If None, it will default to `pool_size`.
      padding: One of `"valid"` or `"same"` (case-insensitive).
        `"valid"` means no padding. `"same"` results in padding evenly to
        the left/right or up/down of the input such that output has the same
        height/width dimension as the input.
      data_format: A string,
        one of `channels_last` (default) or `channels_first`.
        The ordering of the dimensions in the inputs.
        `channels_last` corresponds to inputs with shape
        `(batch, height, width, channels)` while `channels_first`
        corresponds to inputs with shape
        `(batch, channels, height, width)`.
        It defaults to the `image_data_format` value found in your
        Keras config file at `~/.keras/keras.json`.
        If you never set it, then it will be "channels_last".

    Input shape:
      - If `data_format='channels_last'`:
        4D tensor with shape `(batch_size, rows, cols, channels)`.
      - If `data_format='channels_first'`:
        4D tensor with shape `(batch_size, channels, rows, cols)`.

    Output shape:
      - If `data_format='channels_last'`:
        4D tensor with shape `(batch_size, pooled_rows, pooled_cols, channels)`.
      - If `data_format='channels_first'`:
        4D tensor with shape `(batch_size, channels, pooled_rows, pooled_cols)`.

    Returns:
      A tensor of rank 4 representing the maximum pooled values.  See above for
      output shape.
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