# what's the secret to making a good robot in robocode

Fragment of a discussion from User talk:Tmservo

Basically, I don't think GuessFactors assume anything (besides symmetry) that isn't already true based on the physics of Robocode. Your input to firing a shot at your already chosen bullet power is an absolute angle (modulo your current gun heading). A wave collects what should have been the input to that API call. To me that seems about as close to "making no assumptions" as you can get.

So I'm forced to ask myself: why don't you use GFs in Melee? Doesn't that prove they assume an orbital movement? But I really think it's more that you can assume non-orbital movement in Melee, so it's advantageous to do so (PIF, displacement vectors).

03:55, 19 December 2013

I think of "assume non-orbital movement in Melee" and "assume orbital movement in 1v1" as two sides of the same coin. Either way it's an assumption. You could go somewhere in the middle by having both GF-based and PIF-based (and displacement-vector-based) methods and picking the one that seems to best characterize the current enemy, but even then you still make an assumption: That the assumption of a fixed method is suboptimal often enough that it's worth the penalty of sometimes picking the wrong one ;)

05:40, 19 December 2013

In practice, they are two sides of the same coin, but I still disagree. Only the "assume non-orbital movement" involves extrapolating enemy movements (relative to anything) and translating to and from firing angles. Waves collect very close to the exact value that the Robocode API takes as input to decide if you hit an enemy. That just doesn't feel like adding any assumption that isn't already introduced by Robocode itself.

05:57, 19 December 2013

But on further thought, it's also no excuse to ignore an assumption made by the API. As in, coming up with a model that eliminates an assumption made by the Robocode API would (edit: well, could...) be an improvement to a targeting algorithm. And I'll concede that the Robocode API taking a firing angle as input introduces an assumption of lateral displacement scaling by bullet flight time.

06:12, 19 December 2013

It seems to me that assuming lateral symmetry could be exploited by an opponent. Imagine a bot which started moving clockwise, went to GF .5 . Then for the next wave, its moving counterclockwise, a gun assuming symmetry will fire ahead if it at GF .5 relative to its orbit direction. It is not looking at GF relative to orbit direction, but absolutely in terms of clockwise and counterclockwise. It moves again to absolute GF .5. It continues to always move to absolute GF .5, but predicts enemy firing times and arranges to alternate orbiting clockwise and counterclockwise when they fire. This simple version would probably be much more effective against guns with fast data decay.

02:20, 20 December 2013

Hmm. But if you're already tracking stats from the enemy's perspective, isn't it more effective to just use the same model as they are and avoid the dangerous spots? I don't need any symmetry tricks to know the enemy will shoot at GF 0.5 (from his perspective) and not go there.

I'm curious what MN and Rednaxela have to say. :-) I'm thinking it might be exploitable by a non-surfing movement, but for a surfing movement you are sacrificing more than your'e gaining.

02:34, 20 December 2013

Im not saying my system is a particularly good one, it just shows that using relative GFs should technically be exploitable. What you are saying, knowing enemy will shoot at .5, is basically using a flattener.

03:22, 20 December 2013

I don't know, I think to me the definition of "exploiting" means you can use it to improve your system. Tweaking a random movement to have a non-symmetric profile could be an improvement. With surfing, your goal is to model the enemy's targeting data model, which is done correctly by assuming symmetrical GFs. It seems to me a surfing movement is already aware of the GF symmetry and taking it into account as best it can.

03:34, 20 December 2013

From the perspective of normal (relative to orbit direction) GFs, what it comes down to is that you'd have is a movement which alternates between GF 0.5 and GF -0.5.

It's true like you say that this could have some level of effectiveness against targeting systems that are using firing waves only AND are missing certain segmentation dimensions...

I would say it could be 'exploiting' yes, but I would also guess there are very few targeting systems you'd reliably trick with this. It seems extremely fragile. Your maneuvers to "arrange to alternate orbiting ..." would give away which of GF 0.5 and GF -0.5 you're heading to in certain targeting segments/dimensions (easy near-100% hit rate against it), and even without that, asymmetry in the result of non-firing waves would cause a lean toward one or the other, causing an easy ~50% hit rate.

It would be interesting to see a demonstration of what in practice would be tricked by it though.

16:05, 20 December 2013