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from itertools import product
from sympy import symbols, exp, log, S
from sympy.codegen.numpy_nodes import logaddexp, logaddexp2

x, y, z = symbols('x y z')

def test_logaddexp():
    lae_xy = logaddexp(x, y)
    ref_xy = log(exp(x) + exp(y))
    for wrt, deriv_order in product([x, y, z], range(0, 3)):
        assert (
            lae_xy.diff(wrt, deriv_order) -
            ref_xy.diff(wrt, deriv_order)
        ).rewrite(log).simplify() == 0

    one_third_e = 1*exp(1)/3
    two_thirds_e = 2*exp(1)/3
    logThirdE = log(one_third_e)
    logTwoThirdsE = log(two_thirds_e)
    lae_sum_to_e = logaddexp(logThirdE, logTwoThirdsE)
    assert lae_sum_to_e.rewrite(log) == 1
    assert lae_sum_to_e.simplify() == 1
    assert logaddexp(2, 3).simplify() == logaddexp(2, 3)  # cannot simplify with 2, 3


def test_logaddexp2():
    lae2_xy = logaddexp2(x, y)
    ref2_xy = log(2**x + 2**y)/log(2)
    for wrt, deriv_order in product([x, y, z], range(0, 3)):
        assert (
            lae2_xy.diff(wrt, deriv_order) -
            ref2_xy.diff(wrt, deriv_order)
        ).rewrite(log).simplify() == 0

    def lb(x):
        return log(x)/log(2)

    two_thirds = S.One*2/3
    four_thirds = 2*two_thirds
    lbTwoThirds = lb(two_thirds)
    lbFourThirds = lb(four_thirds)
    lae2_sum_to_2 = logaddexp2(lbTwoThirds, lbFourThirds)
    assert lae2_sum_to_2.rewrite(log) == 1
    assert lae2_sum_to_2.simplify() == 1
    assert logaddexp2(x, y).simplify() == logaddexp2(x, y)  # cannot simplify with x, y