import unittest

import numpy as np

from gradient_checker import GradientChecker, create_op
from op_test_util import OpTestMeta


def stable_softmax(x):
    """Compute the softmax of vector x in a numerically stable way."""
    shiftx = x - np.max(x)
    exps = np.exp(shiftx)
    return exps / np.sum(exps)


class TestSoftmaxOp(unittest.TestCase):
    __metaclass__ = OpTestMeta

    def setUp(self):
        self.type = "softmax"
        self.inputs = {"X": np.random.random((10, 10)).astype("float32")}
        self.outputs = {
            "Y": np.apply_along_axis(stable_softmax, 1, self.inputs["X"])
        }


class TestSoftmaxGradOp(GradientChecker):
    def setUp(self):
        self.op = create_op("softmax")
        self.inputs = {
            "X": np.random.uniform(0.1, 1, [10, 10]).astype("float32")
        }

    def test_softmax_grad(self):
        self.check_grad(self.op, self.inputs, ["X"], "Y")


if __name__ == "__main__":
    unittest.main()