chore: import upstream snapshot with attribution

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

@@ -0,0 +1,24 @@
+import unittest
+import numpy as np
+from prml import nn
+
+
+class TestLog(unittest.TestCase):
+
+    def test_log(self):
+        x = nn.Parameter(2.)
+        y = nn.log(x)
+        self.assertEqual(y.value, np.log(2))
+        y.backward()
+        self.assertEqual(x.grad, 0.5)
+
+        x = np.random.rand(4, 6)
+        p = nn.Parameter(x)
+        y = nn.log(p)
+        self.assertTrue((y.value == np.log(x)).all())
+        y.backward(np.ones((4, 6)))
+        self.assertTrue((p.grad == 1 / x).all())
+
+
+if __name__ == '__main__':
+    unittest.main()