ThreadDeath problem

Fragment of a discussion from Talk:RoboRumble
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Skipped turns are logged (and SkippedTurnEvents happens) only when the Robocode regains control over the execution of the thread. Since there is an unhandled exception being thrown right during the skipped turn checking, it makes sense that the skipped turns are not logged. I'm pretty sure you are skipping too many turns, Thread.stop() is being called as it is supposed to be (by looking at Robocode source), the exception is being thrown (because Thread.stop() is deprecated) and for some reason it's not being handled.

So, the error message is pretty much "you have skipped too many turns, I tried to stop your thread but for this I called a deprecated function which throws an error". The bot punishment for skipping too many turns is correct. The correct questions are: this should really happen? not the error, but the "too many skipped turns" thing. Does it happen when locking to 1000 FPS? If it was a "fair" turn skipping, it should happen while locked to 1000 FPS as well? If yes, why it's behaving differently when on full speed? Can others reproduce the same issue? (pick Roborio vs Neuromancer, for example, and go full speed). Why it's more likely to happen when a slow bot is against a fast bot? And so on.

Does you guys have any other interesting observations on that?

Rsalesc (talk)03:35, 5 September 2017

Ok. Roborio also fall into ThreadDeath in the battle:

rsalesc.roborio.Roborio 1.2.7  vs penguin.Joker .611wr

It does not happens at 1000 FPS, only if I push the slider to max.

I also see DrussGT falling into ThreadDeath in the battle:

jk.mega.DrussGT 3.2.1 vs penguin.Joker .611wr

It seems that in a pair of bots the most CPU demanding gets the exception.

Beaming (talk)04:33, 5 September 2017

Yeah, here is the heart of the issue in my opinion. Weird things going under the hood when going full speed. I still have not fully understood Robocode skipped turn source so I'm not sure what's happening. I'll do more tests tomorrow.

Rsalesc (talk)12:51, 5 September 2017

I looked at the internals. The difference between desired 1000 TPS and max is that in the later case the Thread.sleep is called (actually if you have more than 0.5 ms to spare). I am guessing that probabilistically Thread.Sleep is called couple times per round.

I do not know what java does when thread is asleep, but I would imagine that the garbage collector and other gizmos kick in during the sleep. While at max TPS the java chooses as it wishes when to run GC and if you are the unlucky one, the GC time will be counted against your bot. This would explain sporadic super long executions in my bot time profiling.

Beaming (talk)19:45, 5 September 2017