chore: import upstream snapshot with attribution

books/PRML/PRML-master-Python/test/nn/math/negative.py

@@ -0,0 +1,24 @@
+import unittest
+import numpy as np
+from prml import nn
+
+
+class TestNegative(unittest.TestCase):
+
+    def test_negative(self):
+        x = nn.Parameter(2.)
+        y = -x
+        self.assertEqual(y.value, -2)
+        y.backward()
+        self.assertEqual(x.grad, -1)
+
+        x = np.random.rand(2, 3)
+        xp = nn.Parameter(x)
+        y = -xp
+        self.assertTrue((y.value == -x).all())
+        y.backward(np.ones((2, 3)))
+        self.assertTrue((xp.grad == -np.ones((2, 3))).all())
+
+
+if __name__ == '__main__':
+    unittest.main()