def mullers_single(mu, sigma, single=True):
    while True:
        x, y = np.random.ranf(2)*2 - 1
        s = x**2 + y**2
        if 0 < s <= 1:
            break
    logs = math.sqrt(-2.*math.log(s) / s)
    z0 = x * logs
    z1 = y * logs
    if single:
        return z0 * sigma + mu
    else:
        return [z0 * sigma + mu, z1 * sigma + mu]
        
def muller(mu, sigma, n):
    if nsize == 1:
        return mullers_single(mu, sigma)
    res = []
    for i in xrange(n / 2):
        res += mullers_single(mu, sigma, single=False)
    if nsize % 2 != 0:
        res.append(mullers_single(mu, sigma))
    return res