utils.py 文件源码

def log_combination(n, ks):
    """
    Compute the log combination function.

    .. math::

        \\log \\binom{n}{k_1, k_2, \\dots} = \\log n! - \\sum_{i}\\log k_i!

    :param n: A N-D `float` Tensor. Can broadcast to match `ks[:-1]`.
    :param ks: A (N + 1)-D `float` Tensor. Each slice `[i, j, ..., k, :]` is
        a vector of `[k_1, k_2, ...]`.

    :return: A N-D Tensor of type same as `n`.
    """
    return tf.lgamma(n + 1) - tf.reduce_sum(tf.lgamma(ks + 1), axis=-1)