def get_diff_idxs(array, rtol, atol):
    """
    Given an array with (C, N, L) values, being the first the reference value,
    compute the relative differences and discard the one below the tolerance.
    :returns: indices where there are sensible differences.
    """
    C, N, L = array.shape
    diff_idxs = set()  # indices of the sites with differences
    for c in range(1, C):
        for n in range(N):
            if not numpy.allclose(array[c, n], array[0, n], rtol, atol):
                diff_idxs.add(n)
    return numpy.fromiter(diff_idxs, int)
Given an array with (C, N, L) values, being the first the reference value,
    compute the relative differences and discard the one below the tolerance.
    :returns: indices where there are sensible differences.