Changing a Timer¶

Some changes in a model’s timers might break fingerprints, but otherwise wouldn’t invalidate the model, such as timers which don’t affect the model’s behavior. However, the change in the timers might break the default ingredient fingerprint tests. In such case, the events or modules that contain the timer need to be filtered:

• Before making the change, filter the events or modules which involve the affected timer, and calculate the fingerprints

• Accept the new fingerprint values

• Make the change

• Rerun the fingerprint tests with the same filtering

The tests should pass.

As a simplistic example, we’ll change how the removeNonInterferingTransmissionsTimer is scheduled in RadioMedium.cc. The timer deletes transmissions that no longer cause any interference (e.g. they have already left the vicinity of network nodes).

We run the simulation and filter the events of the timer. We use the inet command in the tutorial directory. The fingerprint 0000-0000/tplx is a dummy value. It makes the run fail, and the run prints the calculated value:

$ inet -u Cmdenv -c Wifi -r 0 --sim-time-limit=5s --fingerprint=0000-0000/tplx --fingerprint-events='"not name=~removeNonInterferingTransmissions"'

Fingerprint mismatch! calculated: XXXX-XXXX/tplx, expected: 0000-0000/tplx

Note the calculated value. The model did not change. The filter changed the set of events that the fingerprint uses. The command does not change the store, so the stored tplx values stay as they are.

Now, we change the timer:

--- /home/runner/work/inet/inet/tutorials/fingerprint/sources/RadioMedium.cc.orig
+++ /home/runner/work/inet/inet/tutorials/fingerprint/sources/RadioMedium.cc.mod
@@ -233,7 +233,7 @@
     communicationCache->mapTransmissions([&] (const ITransmission *transmission) {
         auto interferenceEndTime = communicationCache->getCachedInterferenceEndTime(transmission);
         if (!removeNonInterferingTransmissionsTimer->isScheduled() && interferenceEndTime > simTime())
-            scheduleAt(interferenceEndTime, removeNonInterferingTransmissionsTimer);
+            scheduleAt(interferenceEndTime + 1E-6, removeNonInterferingTransmissionsTimer);
     });
 }
 

We run the simulation again with the same filter and the calculated fingerprint:

$ inet -u Cmdenv -c Wifi -r 0 --sim-time-limit=5s --fingerprint=XXXX-XXXX/tplx --fingerprint-events='"not name=~removeNonInterferingTransmissions"'

Fingerprint successfully verified

The model is verified. The fingerprints can be calculated without filtering. Then the update command records the new values in the store. This process is described in more detail in the Accepting Fingerprint Changes step.