Randarts and power

[Nick]

First, some context.

Randarts have a long history in Angband. Since about 3.2, they have principally been a labour of love for Magnate, who spent a lot of time and effort refining the randart generation to the point where everyone seems to be pretty happy with it in 4.0.5.

So I'm about to break them. Here are my reasons:

1. Objects used to only be allowed to have one value (the "pval") which could be used as a bonus to stats, speed, stealth, etc. This changed first to allowing three such values ("multiple pvals"), and now to the ability to have as many as there are such modifiers. But the randart code still behaves as if it's the one pval era, which seems an unnecessary restriction.
2. Randarts work by calculating a power value for all the standard artifacts, then for each one generating a replacement of similar power. This power calculation can in fact be done for any object; it is also used for determining shop prices. Now there is also a monster power calculation, and these two depend on each other. This power calculation code is quite intricate, and has had some strange fudge factors put in to make all the final answers look sensible. This is all very well, but it means the power calculations are very sensitive to changes in the object or monster list. I would like to make it so that changes to objects and monsters can be made without having to retune power.
3. More generally, a big part of my aim in restructuring the Angband code was to make it easier to modify sensibly. My insistence on making 4.0.0 gameplay identical to 3.5.1 meant much of the power and randart code had to remain as it was, but now that restriction has been lifted I would like to finish the restructure job for these areas.

So long story short, the nightlies are going to have randarts and object prices which will (to put it kindly) require some balancing for a while. Please play them and give feedback about how the balance is going (note that there is also a bug thread for the nightlies here).

[Estie]

I would be happy to play, but are these changes already in effect ?

Can you give a rough idea of how artifact power depends on monster power and what those fudge factors look like ?

As for shop pricing, giving that there are items I always buy (free action gloves) and ones I never buy (defender weapon), I dont see how changing prices could possibly be unbalancing, unless it is for consumables - but why would those depend on power calculations.

Edit: it seems to be in effect alreday, I created a randart file and there is artifact with +3 str and +5 stealth, indicating multiple pvals.

[Nick]

Originally Posted by Estie

Can you give a rough idea of how artifact power depends on monster power and what those fudge factors look like ?

Well, power of an artifact includes a power value for its slays and brands. This is worked out by working out the best slay/brand multiplier against each monster, and then calculating an average multiplier against all monsters weighted by the monster power.

Fudge factors - there are many. One example is when calculating the max damage a monster can deal with a melee blow, the current code multiplies that damage by 4/3 if it is a blow that can stun, or by 7/5 if it is a blow that can cut, to give an idea how relatively dangerous that blow is. This seems kind of reasonable, but is also basically just an arbitrary guess, and then there are dozens of these guesses.

I'm not sure exactly what the best way forward is - we may well end up with something quite similar to now, but I'll be thinking about it and I'm happy to hear suggestions.

Originally Posted by Estie

As for shop pricing, giving that there are items I always buy (free action gloves) and ones I never buy (defender weapon), I dont see how changing prices could possibly be unbalancing, unless it is for consumables - but why would those depend on power calculations.

When these power calculations first started, there was, for example, a big drop in the shop price for Boots of Speed. I don't think there will be huge price changes this time, but there may be some; and certainly randarts will be different in ways I can't really predict.

Originally Posted by Estie

Edit: it seems to be in effect already, I created a randart file and there is artifact with +3 str and +5 stealth, indicating multiple pvals.

Yes, the first changes are in the latest nightlies. There will probably be more randart changes as I clean up the code and see what I break

[Pete Mack]

Stunning is way more dangerous than cuts or poison. Stunning and confusion are by far the most dangerous side effects (especially with lanterns of seeing in the game.)

[Magnate]

Good luck my friend. I am lurking and interested - it is a long-held ambition to get rid of all the fudge factors. If there's anything I can do etc.

[Nomad]

Originally Posted by Nick

Fudge factors - there are many. One example is when calculating the max damage a monster can deal with a melee blow, the current code multiplies that damage by 4/3 if it is a blow that can stun, or by 7/5 if it is a blow that can cut, to give an idea how relatively dangerous that blow is. This seems kind of reasonable, but is also basically just an arbitrary guess, and then there are dozens of these guesses.

I'm not sure exactly what the best way forward is - we may well end up with something quite similar to now, but I'll be thinking about it and I'm happy to hear suggestions.

This is probably more reorganising the problem than solving it, but how about moving all the arbitrary multipliers/fudge factors out to an edit file? List all the flags in an edit file and assign them each a numerical "power level"/value corresponding to their relative usefulness/importance (huge can of worms in itself, I know). Then the actual hard-coded power calculation can be clean and simple and just look up how many "points" each trait is worth from the file and plug that number in as a multiplier. Plus it will be easy to make tweaks to the edit file both to balance things after game changes and for individual players who disagree with the existing rankings.

(As for the huge can of worms that is deciding how much individual traits are worth relative to each other in the first place, the only thing I can suggest is getting the community to all list their personal rankings and averaging the results. Which I'm sure will probably devolve into a length derailing argument about some minor point within the first handful of posts, but oh, well. )

[Nick]

Originally Posted by Nomad

This is probably more reorganising the problem than solving it, but how about moving all the arbitrary multipliers/fudge factors out to an edit file? List all the flags in an edit file and assign them each a numerical "power level"/value corresponding to their relative usefulness/importance (huge can of worms in itself, I know). Then the actual hard-coded power calculation can be clean and simple and just look up how many "points" each trait is worth from the file and plug that number in as a multiplier. Plus it will be easy to make tweaks to the edit file both to balance things after game changes and for individual players who disagree with the existing rankings.

Funnily enough, I just had that very thought this morning

A start has already been made on this with constants.txt, but yes, that is the correct thing to do.

Originally Posted by Nomad

(As for the huge can of worms that is deciding how much individual traits are worth relative to each other in the first place, the only thing I can suggest is getting the community to all list their personal rankings and averaging the results. Which I'm sure will probably devolve into a length derailing argument about some minor point within the first handful of posts, but oh, well. )

Well, once they're all in edit files I can just throw my hands up and say "Fix it yourself"

[fizzix]

Originally Posted by Nick

Well, once they're all in edit files I can just throw my hands up and say "Fix it yourself"

What we really need is a good metric for these things. How valuable is slay evil, how about slay undead? slay orc on an early weapon isn't bad, but on a late game weapon is completely worthless. How do we calculate the power of that?

Since these things do depend on the monster list, I don't see any way of getting around the coupling problem. I think this is the natural way to go.

I'm not sure how to go about calculating these metrics in any sort of self-consistent way. This even moreso for "utility" things like speed, damage, telepathy. What's the relative weighting of +3 damage vs. slay troll?

[Pete Mack]

If you really want to know, do a fit based on dlevel statistics in the ladder. But in general, acid brand +slay evil is super powerful, while cold brand and slay animal is not

[fizzix]

Originally Posted by Pete Mack

If you really want to know, do a fit based on dlevel statistics in the ladder. But in general, acid brand +slay evil is super powerful, while cold brand and slay animal is not

Sample size will be nowhere near enough, and furthermore, it won't necessarily scale across versions. For a long time, trident of pain + branding acid ring was a very common combo. That's out of the picture now.