X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=resources%2Flibraries%2Fpython%2FPLRsearch%2FPLRsearch.py;h=0e78cc936d6ddcbaaccb680408d1ce094dda7e1d;hb=d07f6cae7f18c1513650d4cb690115d60201e704;hp=cdfd3081494ac9c246162e60d6011029bcb2165f;hpb=b6fbffad32515ccf94404680cb5280c2cb561af5;p=csit.git

diff --git a/resources/libraries/python/PLRsearch/PLRsearch.py b/resources/libraries/python/PLRsearch/PLRsearch.py
index cdfd308149..0e78cc936d 100644
--- a/resources/libraries/python/PLRsearch/PLRsearch.py
+++ b/resources/libraries/python/PLRsearch/PLRsearch.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2021 Cisco and/or its affiliates.
+# Copyright (c) 2022 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:
@@ -426,13 +426,21 @@ class PLRsearch:
         Integrator assumes uniform distribution, but over different parameters.
         Weight and likelihood are used interchangeably here anyway.
 
-        Each trial has an offered load, a duration and a loss count.
-        Fitting function is used to compute the average loss per second.
-        Poisson distribution (with average loss per trial) is used
+        Each trial has an intended load, a sent count and a loss count
+        (probably counting unsent packets as loss, as they signal
+        the load is too high for the traffic generator).
+        The fitting function is used to compute the average loss rate.
+        Geometric distribution (with average loss per trial) is used
         to get likelihood of one trial result, the overal likelihood
         is a product of all trial likelihoods.
         As likelihoods can be extremely small, logarithms are tracked instead.
 
+        The current implementation does not use direct loss rate
+        from the fitting function, as the input and output units may not match
+        (e.g. intended load in TCP transactions, loss in packets).
+        Instead, the expected average loss is scaled according to the number
+        of packets actually sent.
+
         TODO: Copy ReceiveRateMeasurement from MLRsearch.
 
         :param trace: A multiprocessing-friendly logging function (closure).
@@ -556,6 +564,20 @@ class PLRsearch:
             :rtype: multiprocessing.Connection
             """
 
+            boss_pipe_end, worker_pipe_end = multiprocessing.Pipe()
+            # Starting the worker first. Contrary to documentation
+            # https://docs.python.org/3/library/multiprocessing.html#multiprocessing.connection.Connection
+            # sending of large object without active listener on the other side
+            # results in a deadlock, not in a ValueError.
+            # See https://stackoverflow.com/questions/15137292/large-objects-and-multiprocessing-pipes-and-send
+            worker = multiprocessing.Process(
+                target=Integrator.try_estimate_nd,
+                args=(worker_pipe_end, 10.0, self.trace_enabled)
+            )
+            worker.daemon = True
+            worker.start()
+
+            # Only now it is safe to send the function to compute with.
             def value_logweight_func(trace, x_mrr, x_spread):
                 """Return log of critical rate and log of likelihood.
 
@@ -601,15 +623,6 @@ class PLRsearch:
                 return value, logweight
 
             dilled_function = dill.dumps(value_logweight_func)
-            boss_pipe_end, worker_pipe_end = multiprocessing.Pipe()
-            # Do not send yet, run the worker first to avoid a deadlock.
-            # See https://stackoverflow.com/a/15716500
-            worker = multiprocessing.Process(
-                target=Integrator.try_estimate_nd,
-                args=(worker_pipe_end, 10.0, self.trace_enabled)
-            )
-            worker.daemon = True
-            worker.start()
             boss_pipe_end.send(
                 (dimension, dilled_function, focus_tracker, max_samples)
             )