keras/src/activations/activations.py/hard_silu
def hard_silu(x):
    """Hard SiLU activation function, also known as Hard Swish.

    It is defined as:

    - `0` if `if x < -3`
    - `x` if `x > 3`
    - `x * (x + 3) / 6` if `-3 <= x <= 3`

    It's a faster, piecewise linear approximation of the silu activation.

    Args:
        x: Input tensor.

    Reference:

    - [A Howard, 2019](https://arxiv.org/abs/1905.02244)
    """
    x = backend.convert_to_tensor(x)
    return ops.hard_silu(x)