import torch


def kl_reverse(logu: torch.Tensor) -> torch.Tensor:
    """
    Log-space Csiszar function for reverse KL-divergence D_f(p,q) = KL(q||p).

    Also known as the exclusive KL-divergence and negative ELBO, minimizing
    results in zero-forcing / mode-seeking behavior.

    Args:
        logu (torch.Tensor): ``p.log_prob``s evaluated at samples from q.
    """
    return -logu