Utils.py 文件源码

def get_perplexity(dictionary):
    """Compute the perplexity (=exp entropy) of a dictionary"""
    my_sum = 0
    weighted_sum_of_logs = 0
    for freq in itervalues(dictionary):
        if freq:
            my_sum += freq
            weighted_sum_of_logs += freq * math.log(freq)
    return math.exp(math.log(my_sum) - weighted_sum_of_logs / my_sum)