IETF: Update MLRsearch draft

Change-Id: I591b76b72868697242cfbece8f569dc82128ed85
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

3 files changed, 20 insertions, 11 deletions

diff --git a/resources/libraries/python/MLRsearch/MultipleLossRatioSearch.py b/resources/libraries/python/MLRsearch/MultipleLossRatioSearch.py
index dd21444496..0e6c8cfa58 100644
--- a/resources/libraries/python/MLRsearch/MultipleLossRatioSearch.py
+++ b/resources/libraries/python/MLRsearch/MultipleLossRatioSearch.py
@@ -330,6 +330,7 @@ class MultipleLossRatioSearch:
         cur_lo1, cur_hi1, pre_lo, pre_hi, cur_lo2, cur_hi2 = bounds
         pre_lo_improves = self.improves(pre_lo, cur_lo1, cur_hi1)
         pre_hi_improves = self.improves(pre_hi, cur_lo1, cur_hi1)
+        # TODO: Detect also the other case for initial bisect, see below.
         if pre_lo_improves and pre_hi_improves:
             # We allowed larger width for previous phase
             # as single bisect here guarantees only one re-measurement.
@@ -342,6 +343,10 @@ class MultipleLossRatioSearch:
             self.debug(f"Re-measuring lower bound for {ratio}, tr: {new_tr}")
             return new_tr
         if pre_hi_improves:
+            # This can also happen when we did not do initial bisect
+            # for this ratio yet, but the previous duration lower bound
+            # for this ratio got already re-measured as previous duration
+            # upper bound for previous ratio.
             new_tr = pre_hi.target_tr
             self.debug(f"Re-measuring upper bound for {ratio}, tr: {new_tr}")
             return new_tr
@@ -397,7 +402,7 @@ class MultipleLossRatioSearch:
 
         If no second tightest (nor previous) upper bound is available,
         the behavior is governed by second_needed argument.
-        If true, return None, if false, start from width goal.
+        If true, return None. If false, start from width goal.
         This is useful, as if a bisect is possible,
         we want to give it a chance.
 
@@ -414,6 +419,9 @@ class MultipleLossRatioSearch:
         """
         state = self.state
         old_tr = cur_hi1.target_tr
+        if state.min_rate >= old_tr:
+            self.debug(u"Extend down hits min rate.")
+            return None
         next_bound = cur_hi2
         if self.improves(pre_hi, cur_hi1, cur_hi2):
             next_bound = pre_hi
@@ -427,9 +435,6 @@ class MultipleLossRatioSearch:
             old_tr, old_width, self.expansion_coefficient
         )
         new_tr = max(new_tr, state.min_rate)
-        if new_tr >= old_tr:
-            self.debug(u"Extend down hits max rate.")
-            return None
         return new_tr
 
     def _extend_up(self, cur_lo1, cur_lo2, pre_lo):
@@ -446,6 +451,9 @@ class MultipleLossRatioSearch:
         """
         state = self.state
         old_tr = cur_lo1.target_tr
+        if state.max_rate <= old_tr:
+            self.debug(u"Extend up hits max rate.")
+            return None
         next_bound = cur_lo2
         if self.improves(pre_lo, cur_lo2, cur_lo1):
             next_bound = pre_lo
@@ -455,9 +463,6 @@ class MultipleLossRatioSearch:
             old_width = max(old_width, state.width_goal)
         new_tr = multiple_step_up(old_tr, old_width, self.expansion_coefficient)
         new_tr = min(new_tr, state.max_rate)
-        if new_tr <= old_tr:
-            self.debug(u"Extend up hits max rate.")
-            return None
         return new_tr
 
     def _bisect(self, lower_bound, upper_bound):
diff --git a/resources/libraries/python/MLRsearch/PerDurationDatabase.py b/resources/libraries/python/MLRsearch/PerDurationDatabase.py
index b069dd921a..afdf48614b 100644
--- a/resources/libraries/python/MLRsearch/PerDurationDatabase.py
+++ b/resources/libraries/python/MLRsearch/PerDurationDatabase.py
@@ -25,7 +25,7 @@ class PerDurationDatabase:
     so the logic is quite simple.
 
     Several utility methods are added, accomplishing tasks useful for MLRsearch
-    (to be called by MeasurementDatabade).
+    (to be called by MeasurementDatabase).
     """
 
     def __init__(self, duration, measurements):
@@ -61,6 +61,8 @@ class PerDurationDatabase:
         """Sort by target_tr, fail on detecting duplicate target_tr.
 
         Also set effective loss ratios.
+
+        :raises ValueError: If duration does not match or if TR duplicity.
         """
         measurements = self.measurements
         measurements.sort(key=lambda measurement: measurement.target_tr)
diff --git a/resources/libraries/python/MLRsearch/WidthArithmetics.py b/resources/libraries/python/MLRsearch/WidthArithmetics.py
index 81decfd12f..21316c5441 100644
--- a/resources/libraries/python/MLRsearch/WidthArithmetics.py
+++ b/resources/libraries/python/MLRsearch/WidthArithmetics.py
@@ -54,10 +54,12 @@ def halve_relative_width(relative_width, goal_width):
     fallback_width = 1.0 - math.sqrt(1.0 - relative_width)
     # Wig means Width In Goals.
     wig = math.log(1.0 - relative_width) / math.log(1.0 - goal_width)
-    cwig = math.ceil(wig)
-    if wig <= 2.0 or cwig != math.ceil(wig * ROUNDING_CONSTANT):
+    cwig = 2.0 * math.ceil(wig / 2.0)
+    fwig = 2.0 * math.ceil(wig * ROUNDING_CONSTANT / 2.0)
+    if wig <= 2.0 or cwig != fwig:
+        # Avoid too uneven splits.
         return fallback_width
-    coefficient = cwig // 2
+    coefficient = cwig / 2
     new_width = multiply_relative_width(goal_width, coefficient)
     return new_width