Easy Question?

Hi mates.

How to detect inactivity?

It sounded like an easy problem to solve but now i struggle with it for quite a while and i guess i ask a little around now.

My solution so far is - counting all energy drops of my bot and if the energy difference has a value of 0.1 the inactivity timer has kicked in. Well, it works not very well and is quite a lot of code to just detect inactivity. Wall hits and inactivity is something that does not work very well for now. Has anyone solved this problem or might have a simpler solution? Any ideas would be gladly appreciated.

If you ask - why does he bother with inactivity? - well, i have no answer that doesn't sounds nitpicking.

How about if they dropped 0.1 and you drop 0.1 in the same tick? That should cancel out most cases, except maybe extreme endgame. If they drop 0.1 several ticks in a row then you can be sure that they weren't just firing.

Well that is similar to what I do in Nene. I just check if the power was 0.1 and the last time I detected them firing was 1 turn ago. Since I don't count my own bullets damaging them as 'them firing', this works out very well in a normal rumble.

I also remove the last wave if I added one. This is 'safe' because if they fired there isn't going to be an inactivity counter kicking in the turn after they fired. But just to be safe, I only assign the 'lastWave' and 'lastWaveFireTime' variables if the power is equal to 0.1 (or rather within 0.001 of 0.1), specifically for the anti-activity counter.

@Skilgannon - this sounds like a good idea to recheck my energy drop against the enemy drop if i hit a wall. Because in all other cases i can detect inactivity 100% based on my energy profile and just adjust the enemy energy on that. Actually i came to think about inactivity because i observed that in melee end games it happens quite frequently that the inactivity timer kicks in (long range and bullets < 1.0). The main "concern" i have, is winning by inactivity makes you loose all bonuses (have to recheck if the bonus get lost for all opponents).

@chase - i hade a quick peek at your code and it looks like you have the same "trouble" with your solution, as i had with my first try. Because an enemy can still shoot <1.0 bullets and the inactivity will not be canceled. This means basically that your waves on inactivity are of by 0.1 bullet power (0.3 pix per turn) . Probably not worth of thinking about it but if you add the uncertainty of wall damage that could become more "serious".

Well, maybe i should explain a little more why i'm nitpicking on this. Based on observations i made on almost all high ranked wave surfer bots, i'm playing with a experimental trick movement for those bots, based on 'forced' wall hits and shooting the same turn i hit the wall. I guess theoretically it could work quite nice and just for the sake of curiosity.

In theory you are quite right. In practice it could be less satisfying than expected. I and probably some more take into account accelerating/decelerating bots, although it will never be 100% proof. Decelerating at the right moment could give you the opportunity to fire a specific bulletpower without detection.
The discussion about inactivity timer got my attention though, I'll see if I can come up with something for my next release.

just an update ... if the opponent dies by inactivity you get no score bonus for him. You also get no bonus if you die by inactivity for all alive opponents. It is still unclear what the conditions for inactivity in melee are. I tested 8 sitting ducks and 2 bots shooting 0.1 bullets and there was no inactivity trigger. Just 2 bots (0.1) and the inactivity kicks in around 450. I tested some other scenarios (3 bots, just shooting till everyone is below 40 energy) to, with very different inactivity behavior.

@GrubbmGait - actually, imagine a bot who drives with speed 4 to the wall and before he hits set speed to 2 and shoots with 1.0. There is no way to detect if it is a bullet or the wall hit damage.

I thought you wanted to detect inactivity because it confuses wave detection and looks like a bunch of 0.1 power waves are being fired. Gun heat tracking can help distinguishing inactivity from 0.1 power bullets being fired.

But trying to use wall hits to conceal a shot will make you bots movement quite predictable.

Analysing the last example, a bot with speed 4 which sets speed to 2 and shoots with power 1.0 will be shown in the opponents radar as a bot which decelerated from speed 4 to 0 and decreased 1.6 energy. Combat would detect a 1.0 power wave being fired (it ignores 0.6 energy drop whenever someone decelerates more than 2 in a single tick). But if it hits the wall with constant speed 2, then the 1.6 energy drop would be ambiguous. It could mean a 1.6 power bullet was fired and the bot stopped, or a wall hit with a 1.0 power bullet being fired. Currently, Combat would guess it is a 1.0 power bullet and if it was a 1.6 power bullet, dodging would be sub-optimal, but it would still react to the firing.

Another worse scenario: You hit the wall with constant speed 2. A false 0.6 power wave would be detected and gun heat tracking would kick in. Then, there would be a 12 tick window when a shot would go undetected. If it is a power 3.0 bullet, it would hit long after the 0.6 wave was dodged. Maybe I should disable gun heat tracking for 0.6 power bullets shot near walls.

If you hit the wall with speed <2.0 you get no wall damage. So the 4 (2) -> 0 shoot 1.0 example would result in an 1.0 energy drop. Same as if you hit the wall with speed 4 and no shooting.

For the inactivity thing - nope it is not to confuse wave detection it just messed with my bullet calculation. I guess i should not bring up 2 different things in one thread, sorry for that. Both things are just related to "Energy drop" and by now i want a almost 100% energy calculation.

I thought all collisions resulted in 0.6 damage. Combat would detect a 0.4 bullet being fired in the example above, and would react to the firing, although it should detect a wall collision with 1.0 damage. Sort of a Performance Enhancing Bug.

The energy drop is ambiguous and the real collision damage is anything between 0.0 and 1.0. Maybe dodging a "thick" wave representing bullet powers from 0.1 to 1.0 can account for this uncertainty. Similar to waves in melee where you don't know exactly in which tick the wave was fired due to gaps in radar scans. And taking extra care with gun heat tracking (maybe assuming the lowest case).

If you hit suddenly slowed before hitting the wall, Nene would assume it hit the wall and did not fire a bullet. Allowing you to get away with a free shot.

But I remind you that slamming into the wall may lower your own score (if you mess up). It also gives a huge and useful data spike and stops your robot. Which means may not work against the top bots very well. Since they are made to capitalize on that. After hitting a wall your avenue of escape is much smaller.

As I have shown with Nene very well, movement trumps targeting. You can hit the top 10 with a gun from 2004 (even if said gun from 2004 was the best from that time).

@MN: check out http://robowiki.net/wiki/Robocode/Game_Physics#Collisions
@Wompi: I detect accelerating/decelerating bots, except when they only do it that last tick before hitting the wall, like your example. That's why I said it is not 100% proof.

As for the inactivity timer, a top bot would not have that situation often. Usually they fire until 0.1 energy left, and then just keep moving. When inactivity timer kicks in, the battle is immediately over. To counter that, you could move closer or even ram the opponent when it stops firing.

Just out curiosity, what is the purpose of keeping track of your own energy? I can't think of anything useful for me.

Tracking your own energy helps detect inactivity damage kicking in. If the opponents energy drops 0.1, it could be due to inactivity or due to a 0.1 power bullet being fired. You can't be sure. But if your own energy drops 0.1 and you didn't shoot, it should be due to inactivity.

Not tracking inactivity damage results in a bunch of false 0.1 power waves being detected at end game. Usually not an issue, but having highly accurate wave detection is cool.

Remembered one case where inactivity damage is a big issue. Reference bots of targeting challenges don't shoot and always outlast candidates with inactivity damage. If they wrongly detect 0.1 power waves, it introduces a lot of noise in their wave histories and makes dodging weaker.

Yes, i'm using a range based calculation for the wall hits right now. The damage range is always 0 to -1.0 or 0 to +0.5 related to the last detected velocity. It makes the enemy gun heat calculation quite difficult.

If you combine the forced wall hit damage with some sort of chase bullet gun it would provide a quite challenging wave pattern, i guess.

And like i said above it is just an experimental movement, nothing to beat a certain bot. I would be happy if i can trick some wave surfer bots a little. To make it fully competitive it would need way more thoughts about it. Mostly i learn some new things while getting along with these experiments and that is the most fun for me.

Actually being predictable is not necessarily a bad thing. For example if you want to use a bullet catcher system to drain the enemy energy to a certain level. On the other hand you can move along the wall and if you time the wall hit, lets say, right after the enemy shoots, you got 10 to 16 + bulletTicks turns to find a better spot or dodge the bullet.

Yes, inactivity is probably nothing to worry about for top bots. But there are some bots out there who shoot always <1.0 bullets and dodging those bots to a certain energy level can take some time.

I'm tracking my energy most of the time for statistics like damage taken, bullets shot, wall damage and i have a energy slop system for me and the enemy to pick my right bullet power. Or better - if he/me looses energy based on his current slop which turn would he be at zero energy.