def random_derangement()

in src/alpaca_eval/utils.py [0:0]

• 12 lines of code
• 7 McCabe index (conditional complexity)

def random_derangement(arr, max_loop=10, seed=None):
    """
    Make random derangement of an array. I.e. shuffle without keeping any element in place. To be efficient,
    we first try `max_loop` rejection sampling. If didn't work then computes all possible derangement.
    """
    if len(arr) < 2:
        return arr

    rng = random.Random(seed)

    idcs = list(range(len(arr)))
    shuffled = list(range(len(arr)))

    for _ in range(max_loop):
        rng.shuffle(shuffled)
        if is_derangement(idcs, shuffled):
            return arr[shuffled]

    # if no luck then computes all possibilities
    deranged_order = list(set([s for s in itertools.permutations(idcs) if is_derangement(s, idcs)]))
    return arr[list(rng.choice(deranged_order))]