keras/src/layers/pooling/max_pooling1d.py

from keras.src.api_export import keras_export
from keras.src.layers.pooling.base_pooling import BasePooling


@keras_export(["keras.layers.MaxPooling1D", "keras.layers.MaxPool1D"])
class MaxPooling1D(BasePooling):
    """Max pooling operation for 1D temporal data.

    Downsamples the input representation by taking the maximum value over a
    spatial window of size `pool_size`. The window is shifted by `strides`.

    The resulting output when using the `"valid"` padding option has a shape of:
    `output_shape = (input_shape - pool_size + 1) / strides)`.

    The resulting output shape when using the `"same"` padding option is:
    `output_shape = input_shape / strides`

    Args:
        pool_size: int, size of the max pooling window.
        strides: int or None. Specifies how much the pooling window moves
            for each pooling step. If None, it will default to `pool_size`.
        padding: string, either `"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: string, either `"channels_last"` or `"channels_first"`.
            The ordering of the dimensions in the inputs. `"channels_last"`
            corresponds to inputs with shape `(batch, steps, features)`
            while `"channels_first"` corresponds to inputs with shape
            `(batch, features, steps)`. 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"`:
        3D tensor with shape `(batch_size, steps, features)`.
    - If `data_format="channels_first"`:
        3D tensor with shape `(batch_size, features, steps)`.

    Output shape:
    - If `data_format="channels_last"`:
        3D tensor with shape `(batch_size, downsampled_steps, features)`.
    - If `data_format="channels_first"`:
        3D tensor with shape `(batch_size, features, downsampled_steps)`.

    Examples:

    `strides=1` and `padding="valid"`:

    >>> x = np.array([1., 2., 3., 4., 5.])
    >>> x = np.reshape(x, [1, 5, 1])
    >>> max_pool_1d = keras.layers.MaxPooling1D(pool_size=2,
    ...    strides=1, padding="valid")
    >>> max_pool_1d(x)

    `strides=2` and `padding="valid"`:

    >>> x = np.array([1., 2., 3., 4., 5.])
    >>> x = np.reshape(x, [1, 5, 1])
    >>> max_pool_1d = keras.layers.MaxPooling1D(pool_size=2,
    ...    strides=2, padding="valid")
    >>> max_pool_1d(x)

    `strides=1` and `padding="same"`:

    >>> x = np.array([1., 2., 3., 4., 5.])
    >>> x = np.reshape(x, [1, 5, 1])
    >>> max_pool_1d = keras.layers.MaxPooling1D(pool_size=2,
    ...    strides=1, padding="same")
    >>> max_pool_1d(x)
    """

    def __init__(
        self,
        pool_size=2,
        strides=None,
        padding="valid",
        data_format=None,
        name=None,
        **kwargs
    ):
        super().__init__(
            pool_size,
            strides,
            pool_dimensions=1,
            pool_mode="max",
            padding=padding,
            data_format=data_format,
            name=name,
            **kwargs,
        )