Added log-domain summation

appengine/findit/libs/math/test/logarithms_test.py

+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import unittest
+
+from libs.math.logarithms import logsumexp
+
+INFINITY = float('inf')
+
+class LogarithmsTest(unittest.TestCase):
+
+  def testLogsumexpEmpty(self):

[Martin Barbella, 2016/12/02 20:07:02]

Docstrings here as well.

[wrengr, 2016/12/02 21:00:58]

Done.

+    self.assertEqual(-INFINITY, logsumexp([]))
+
+  def testLogsumexpInfinite(self):
+    self.assertEqual(INFINITY, logsumexp([INFINITY]))
+    self.assertEqual(INFINITY, logsumexp([INFINITY, -INFINITY]))
+    self.assertEqual(INFINITY, logsumexp([0, 1, 2, INFINITY, 9, 8, 7]))
+
+  def testLogsumexpCommutative(self):
+    # N.B., we must choose these two values carefully, to ensure we
+    # don't trivially pass the test.
+    xs = [0.1, 0.3]
+    ys = xs[::-1]
+    self.assertEqual(logsumexp(xs), logsumexp(ys))