execute() doesn't return

[Jeff Van Epps]

I've started working on an AdvancedRobot, and I find that sometimes the call to execute() just doesn't return. I've got an out.println() right after that which never prints. So far I haven't found a way to trigger it to happen. Other robots in the battle continue executing. onSkippedTurn() isn't being called. What I've asked it to do on the turn when it hangs is sometimes as simple as just a setTurnGunRight(20). Sometimes, when the next round begins, I see this printed:

java.lang.ThreadDeath

at java.lang.Thread.stop(Thread.java:758)

at net.sf.robocode.host.security.RobotThreadManager.stop(RobotThreadManager.java:189)

at net.sf.robocode.host.security.RobotThreadManager.stopSteps(RobotThreadManager.java:171)

at net.sf.robocode.host.security.RobotThreadManager.forceStop(RobotThreadManager.java:142)

at net.sf.robocode.host.security.RobotThreadManager.waitForStop(RobotThreadManager.java:127)

at net.sf.robocode.host.proxies.HostingRobotProxy.waitForStopThread(HostingRobotProxy.java:151)

at net.sf.robocode.host.proxies.BasicRobotProxy.waitForStopThread(BasicRobotProxy.java:43)

at net.sf.robocode.battle.peer.RobotPeer.waitForStop(RobotPeer.java:1670)

at net.sf.robocode.battle.Battle.finalizeRound(Battle.java:386)

at net.sf.robocode.battle.BaseBattle.run(BaseBattle.java:206)

at java.lang.Thread.run(Thread.java:662)

SYSTEM: This robot has been stopped.  No score will be generated.

I'm not starting any threads of my own, or doing any file/network I/O. Really it's nothing but some trig, not that complicated.

Any notions?

Version 1.9.0.0 Running on Java 1.6.0_26 (64-bit) by Sun Microsystems Inc.

on Ubuntu 13.10 64-bit

[fnl]

It seems like your robot is running into an infinite loop somehow. This could be due to e.g. an event handler being called, that calls some method, that triggers the exact same event handler or something else.

The onSkippedTurn() is not called this will only happen if one execute() is executed at time X and another execute() is executed at time Y, and the delta time between X and Y is too big. Then you receive onSkippedTurn() as a notification that you have a serious issue with your robot. When execute() never returns due to an infinite loop, the SkippedTurnEvent never happens.

I recommend that you add some out.println (e.g. out.print("#") ) statements in your run method - especially in loops. You could also add a out.println("onScannedRobot") as the first line for your onScannedRobot() handler and do this for every event handler you have.

If you are lucky you should be able to see which out.print statements that are called too many times. :-)

As alternative, you can send the robot (source file) to me at fnl (at) users.sourceforge.net. Then I will have a look. I will not share the source code with anybody and only keep it temporarily while debugging it.

Cheers,

- Flemming

[Jeff Van Epps]

Good thought. There is already a println as first statement in onScannedRobot() (and the last, so I know when it is getting called it is managing to exit). The only other event handler implemented is onRobotDeath() and there is no loop in it. The only thing it calls is e.getName() to find out who died.

I will email.