Function shuffled_argmax

modAL/utils/selection.py:8–34

Shuffles the values and sorts them afterwards. This can be used to break the tie when the highest utility score is not unique. The shuffle randomizes order, which is preserved by the mergesort algorithm. Args: values: Contains the values to be selected from. n_insta

(values: np.ndarray, n_instances: int = 1)

def shuffled_argmax(values: np.ndarray, n_instances: int = 1) -> np.ndarray:
    """
    Shuffles the values and sorts them afterwards. This can be used to break
    the tie when the highest utility score is not unique. The shuffle randomizes
    order, which is preserved by the mergesort algorithm.

    Args:
        values: Contains the values to be selected from.
        n_instances: Specifies how many indices and values to return.
    Returns:
        The indices and values of the n_instances largest values.
    """
    assert n_instances <= values.shape[0], 'n_instances must be less or equal than the size of utility'

    # shuffling indices and corresponding values
    shuffled_idx = np.random.permutation(len(values))
    shuffled_values = values[shuffled_idx]

    # getting the n_instances best instance
    # since mergesort is used, the shuffled order is preserved
    sorted_query_idx = np.argsort(shuffled_values, kind='mergesort')[
        len(shuffled_values)-n_instances:]

    # inverting the shuffle
    query_idx = shuffled_idx[sorted_query_idx]

    return query_idx, values[query_idx]


def shuffled_argmin(values: np.ndarray, n_instances: int = 1) -> np.ndarray: