Improve PLRsearch yet again

Logic improvements for rls1908 and post-pylint fixes:

+ Reduce search time to 30 minutes.
+ Use average instead alternating loads.
+ Rework log/exp avg/stdev from two estimates.
+ Introduce and use pessimistic variance of dual trackers.
+ Introduce safe_exp to use when None does not skip code.
+ Use dot relative imports (instead of disabling pylint).
+ Complete docstrings for simpler functions.
+ Append docstrings to named tuples.
+ Somewhat unify docstrings related to the same arguments.
+ Slightly improve intentation.
+ State named tuples as rtype where used.
+ Add returns and rtype to __repr__ where missing.
+ Return what docstring say (or update them).
+ Explicit copying for vector and matrix values.

Change-Id: I884c68b4839c5df5e8bef95e463666599603a0ff
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/resources/libraries/python/PLRsearch/log_plus.py b/resources/libraries/python/PLRsearch/log_plus.py
index 3f21cc78d7..1c802a5599 100644
--- a/resources/libraries/python/PLRsearch/log_plus.py
+++ b/resources/libraries/python/PLRsearch/log_plus.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2018 Cisco and/or its affiliates.
+# Copyright (c) 2019 Cisco and/or its affiliates.
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at:
@@ -87,3 +87,16 @@ def log_minus(first, second):
         raise RuntimeError("log_minus: non-positive number to log")
     else:
         return first + math.log(factor)
+
+
+def safe_exp(log_value):
+    """Return exponential of the argument, or zero if the argument is None.
+
+    :param log_value: The value to exponentiate.
+    :type log_value: NoneType or float
+    :returns: The exponentiated value.
+    :rtype: float
+    """
+    if log_value is None:
+        return 0.0
+    return math.exp(log_value)