listwise.py 文件源码

def listpl(x, t, ?=15.0):
    """
    The ListPL loss, a stochastic variant of ListMLE that in expectation
    approximates the true ListNet loss.

    :param x: The activation of the previous layer 
    :param t: The target labels
    :param ?: The smoothing factor
    :return: The loss
    """

    # Sample permutation from PL(t)
    index = _pl_sample(t, ?)
    x = x[index]

    # Compute MLE loss
    final = logcumsumexp(x)
    return F.sum(final - x)