Skill XP Dropoff

[tannisroot]

I've noticed on a SpEn that after a while low level enemies stop providing skill XP. Killing that hobgoblin on D:6 with Throwing at 0.0 and 100% will result in 0 skill xp earned.

Is this determined by the level differential between you and the enemy? Is it better to dive to seek harder enemies at this point?

[bel]

The skill points you get depends on your own XL. So killing a hobgoblin at XL1 will get you much more skill points than killing a hobgoblin at XL27.

You don't need to dive to kill harder enemies: there are plenty of "hard" enemies to kill on D:6 other than hobgoblins. The game tries to have appropriate level monsters at any depth.

[Bart]

Additional benefit from clearing low level areas with relatively strong character is that you can always find some additional resources. Besides, all levels mix somewhat weaker and stronger enemies, so even if a floor seems easy, you might encounter strong enemies just behind the corner.

[Hurkyl]

The greater your skills, the less valuable skill points are. Nominally, training a skill from 0 to 1 takes 50 skill points. However, if I understand the mechanics of this correctly, at the beginning of the game, skill points get amplified by a factor of 10, so you only actually need 5 skill points to train from level 0 to level 1. Towards the end of the game, however, it takes something like 1325 skill points to train from level 0 to level 1. (this is the cap on the "penalty")

A hobgoblin always* gives the same number of skill points, no matter when you kill it; it's just you're getting less use out of those skill points as you level up.

*: I'm not sure if and how this is affected by having allies (or other things) deal damage or by draining.

[njvack]

*: I'm not sure if and how this is affected by having allies (or other things) deal damage or by draining.

Allies matter, draining does not.

Having allies kill things is still good.

[braveplatypus]

How exactly does this drop off work when it comes to race aptitudes, would putting all skills into a +4 would trigger it faster then putting the same exp into a -1? does your races level modifier matter?

This is an even crazier hidden mechanic then GDR. Definitely going to think twice before i trickle into stealth next time.

[tannisroot]

So if I understand correctly: while enemy skill xp is static, the amount skill points required per level is a positive function increasing with player level?

Citing the OP's example: while that hobgoblin is still awarding 50xp at D:6, the amount of skill points required to move from 0.0 to 0.1 throwing is now so high it doesn't register. But killing 100 hobgoblins would. Is that correct?

[MainiacJoe]

Here is how it seems to me:

1. To go from Throwing 0.0 to Throwing 1.0 takes 50 skill points.
2. Skill aptitude converts XP earned into skill points.
3. The Spriggan in the OP is aptitude +1 for throwing. It takes (50 SP) * (2^(-1/4) XP/SP) = 42 XP to get to Throwing 1.0 from Throwing 0.0.
4. The wiki states that hobgoblins are worth 2XP. If allies kill it, it's worth less, but let's ignore that.
5. The 2 XP from the hobgoblin is less than the 4.2 XP needed to go from Throwing 0.0 to Throwing 0.1.

The OP's observations seem to be exactly what one would expect. The dungeon level on which the hobgoblin is encountered is immaterial. Hobgoblins give 2 XP, which is converted (for throwing for Spriggans) into (2 XP)/(42 XP/50 SP) = 2.381 skill points, always. The current skill level doesn't matter either. It will always be 2.381 skill points from a hobgoblin, but the amount of skill points between skill levels does increase. And of course if you distribute your XP amongst several skills, you multiply the total XP from the monster by the percentage in each skill before applying each skill's aptitude adjustment to get each skill's SP gain.

[Pollen_Golem]

2.381 skill points, always.

It seems that this is further curtailed slightly by your XL: the higher your XL, the less skill points that goblin gives.
Edit: or something functionally equivalent.

[dowan]

I think it's actually the higher your XL, the more skill points required to increase skill level. Although in the end these both lead to the same situation, you gotta kill a lot more goblins to go from 0 to 1 as your XL goes up.

[MainiacJoe]

I don't know for sure whether XP given by a monster is passed into a XL-based step-down. It seems to me that a fixed XP > SP function based only on aptitude, combined with a fixed table of increasing SP between skill levels, is both inherently elegant in its simplicity and also able to explain the apparent slow-down of XP effect that we see as the game progresses.

[Pollen_Golem]

If that were the case, you would be able to increase skills at an incredible rate (from 0 to 14 in a couple of real-life minutes, I guess) farther in the game.
Not that I can tell whether that would be better or worse.

[duvessa]

It will always be 2.381 skill points from a hobgoblin, but the amount of skill points between skill levels does increase.

This is literally the opposite of what happens. The number of skill points required for a specific skill level at a specific aptitude is always the same. The amount of XP required to get a skill point increases as you gain XP.

[Arrhythmia]

I don't know for sure whether XP given by a monster is passed into a XL-based step-down.

It is.

[duvessa]

I don't know for sure whether XP given by a monster is passed into a XL-based step-down.

It is.

It's based on collected XP, not XL.

[MainiacJoe]

It will always be 2.381 skill points from a hobgoblin, but the amount of skill points between skill levels does increase.

This is literally the opposite of what happens. The number of skill points required for a specific skill level at a specific aptitude is always the same. The amount of XP required to get a skill point increases as you gain XP.

Thank you.

I have to say, I looked at the wiki article for skills and it didn't mention this step-down at all. So I looked up "skill points" and it did mention the stepdown, but the article as a whole is quite confusing. So this will sound petulant, but it's not: how ought I have gone about learning this? what is the reliable source for game mechanics, especially given how quickly the game changes?

[Pollen_Golem]

I think the correct way to experience Crawl, as originally intended by Linley Hanzell and subsequently the Stone Soup dev team, is to be constantly confused about how the game mechanics work.

[dowan]

I think the correct way to experience Crawl, as originally intended by Linley Hanzell and subsequently the Stone Soup dev team, is to be constantly confused about how the game mechanics work.

This is true, but it's also VERY important that you get a number of conflicting and confusing explanations on how those game mechanics work. The tavern is an excellent place for this.

[MainiacJoe]

I know, and now I'm a contributor to confusion not just a partaker!

[Arrhythmia]

It will always be 2.381 skill points from a hobgoblin, but the amount of skill points between skill levels does increase.

This is literally the opposite of what happens. The number of skill points required for a specific skill level at a specific aptitude is always the same. The amount of XP required to get a skill point increases as you gain XP.

Thank you.

I have to say, I looked at the wiki article for skills and it didn't mention this step-down at all. So I looked up "skill points" and it did mention the stepdown, but the article as a whole is quite confusing. So this will sound petulant, but it's not: how ought I have gone about learning this? what is the reliable source for game mechanics, especially given how quickly the game changes?

You aren't.

[duvessa]

tbh the only reliable source on these things is reading the source code itself, you could probably ask most of the devteam (and me) how skill training works and get wrong answers if any

[MainiacJoe]

You aren't.

???

[Arrhythmia]

You aren't.

???

That the mechanic is so ridiculously obfuscated, that basically no one knows about it, and that knowing about it would have no effect on your game, all this comes together into "you really aren't supposed to know this".

[Sar]

Well, the fact that skills become harder to raise further in the game becomes pretty obvious as you play Crawl. I think the purpose of that is fairly obvious as well. I don't think one needs to know finer details here. What for?

[dowan]

Yeah, an in depth knowledge of GDR would be more useful than a thorough understanding of this system. I do imagine such a complicated system might make it hard to make further changes to how skills and XP work though.

[bel]

There is no need to know the precise details. The behaviour is what you would expect if you didn't know anything. At least I assumed it was this way, even before I read this stuff. In my own mind, the mechanism was reduced XP for killing low-level monsters, but the idea is the same. Killing a hobgoblin at XL10 shouldn't be rewarded the same way as when you kill it at XL1. This is also why higher XLs take much more XP to get.

[braveplatypus]

I don't think it's intuitive that it takes way more goblins to raise your weapon skill to 0 to 1 then it took to raise your fighting skill from 0 to 1 because of the order you chose to raise them in. Knowing that changes my decisions especially when it comes to adding "just a few points" to some off build skills like stealth.

[Sprucery]

It should not really affect your skilling decisions at all. As you progress in the game, you kill monsters that give more experience than goblins. There's plenty enough experience in the game.

[Sandman25]

IMHO another thing is more important.
Skill 7 costs 1400 skill points
skill 8 costs 1800
skill 9 costs 2250
skill 10 costs 2800
skill 11 costs 3450
skill 12 costs 4200
skill 13 costs 5050
and so on.
"Just 1 more level" can be a very bad idea and it is not visible.

[savageorange]

IMHO another thing is more important.
Skill 7 costs 1400 skill points
skill 8 costs 1800
skill 9 costs 2250
skill 10 costs 2800
skill 11 costs 3450
skill 12 costs 4200
skill 13 costs 5050
and so on.
"Just 1 more level" can be a very bad idea and it is not visible.

From that pov, perhaps the display should look like "Armour 2.2 (2)", where (2) is sqrt(skill_points_to_next_integer_skill_level) / 7. This value would range from 1 (at XL1, training a skill to SL1) to 401 (at XL27, training a skill to SL27). If we wanted it to go from 1 to 27*3 (=81), I guess we could put it through a stepdown.

[Sandman25]

Yes, some number for comparison skills can be very useful. Player just should know nature of the numbers (linear, logarithmic, square etc.) to know how Armour 2.2 (2) relates to Dodging 4.0 (7)

[Sprucery]

I think it would be clearer then to just show the amount of skill points needed for the next integer level: Armour 2.2 (143), Dodging 4.0 (298), for example (assuming -1 apt in both).

[bel]

I don't think it's intuitive that it takes way more goblins to raise your weapon skill to 0 to 1 then it took to raise your fighting skill from 0 to 1 because of the order you chose to raise them in. Knowing that changes my decisions especially when it comes to adding "just a few points" to some off build skills like stealth.

That is not the correct question. You are not going to find as many goblins on D:10 as you do on D:1. On D:10, you find D:10 level monsters (and therefore roughly tuned to your XL). So you need to kill roughly the same number of them to raise a skill from 0 to 1, as the number of goblins you killed on D:1 earlier.

[savageorange]

I think it would be clearer then to just show the amount of skill points needed for the next integer level: Armour 2.2 (143), Dodging 4.0 (298), for example (assuming -1 apt in both).

What about rounding off the last digit? That would reduce the maximum length from 4 ("2750") to 3("275"), which may be relevant to console with default settings.
Ideally we could reduce this to 2 digits, but the closest I've come to a good divisor, 25, produces 98 as maximum value rather than 99. Rounding up would fix that, maybe.

[Sandman25]

I considered and discarded this idea (before making my earlier post), because I was working under the assumption that showing large numbers (like 24950) is bad and also problematic for console default settings.

The same here except I thought those numbers were displayed in some old version and then removed later.

[Pollen_Golem]

I don't think it's intuitive that it takes way more goblins to raise your weapon skill to 0 to 1 then it took to raise your fighting skill from 0 to 1 because of the order you chose to raise them in.

I guess it's like this: when you're 5 years old, writing a single word can be a challenge you learn a lot from. When you're older, you don't learn nearly as much from writing a single word, even if you're trying to master penmanship.

[ontoclasm]

Knowing that changes my decisions especially when it comes to adding "just a few points" to some off build skills like stealth.

This is exactly why it's left hidden.

e: To clarify, I mean "because you've just decided, based on this information, to do something not at all warranted by said information."

[Hurkyl]

Knowing that changes my decisions especially when it comes to adding "just a few points" to some off build skills like stealth.

This is exactly why it's left hidden.

e: To clarify, I mean "because you've just decided, based on this information, to do something not at all warranted by said information."

You can say it's not warranted, but that doesn't make it true. If nothing else, realizing that your estimation of the cost of training a few skill levels is off by a factor of ten or even a hundred really changes a lot.

[tannisroot]

This mechanic increases the opportunity cost of skill choice and prevents advancement of low level skills from becoming trivial later in the game.

This might change my behavior in that I would be more careful about what to train for the first few levels.

[Sandman25]

This mechanic increases the opportunity cost of skill choice and prevents advancement of low level skills from becoming trivial later in the game.

This might change my behavior in that I would be more careful about what to train for the first few levels.

That would be a mistake. 50 skill points spent to reach skill level 1 with aptitude 0 is neglectable when skill 13 costs 5050, for example.
You should train whatever it takes to increase your chances to survive now because the cost is very small when comparing with higher level skills which you will reach later.

[GlassGo]

All these talks about "how many goblins needed to screw in a light bulb", errr, to rise one skill level, remembered me that every Hero on his Orb run makes an army of hobgoblin's widows and orphans in every dungeon run.
Just look at him - a wry mouth and crooked rotten teeth, goggle-eyes without a shadow of thought, low crooked frail figure.
Is he a treat? Lets tell a truth - no, he is a unlucky jerk, who find himself on a way of steamroller, and after you bludgeon him to bloody pulp, there are somewhere his crying ugly unhappy wife and several of his children...

[Pollen_Golem]

Lighten up, man, did a steamroller run over your family or something?

[Lasty]

GlassGo, this is crawl. There are also plenty of crying ugly unhappy husbands.

[archaeo]

Would it be possible to at least mention the fact that skills cost most XP with every level? I just looked through the help screen in the skill menu, and there's no mention of this in-game. I can understand the resistance to putting a whole table or graph in the help menu, but something as simple as, "Every level in a skill costs progressively more XP than the previous level," would at least make it clear for crawlers who don't interact much with the online community.

I'd also be a fan of including a single example/rule of thumb, like, "For example, raising a skill from level 20 to 27 requires as much experience as raising a skill from level 0 to 20."

[GlassGo]

Lighten up, man, did a steamroller run over your family or something?

You don't have sense of humor, don't you? ))

[Savant]

I did some source diving because I hadn't heard about this before, and I think I figured out what the mechanics for skill costs are. What follows is based on the skills.cc source file.

First, your character has a hidden level called skill_cost_level (SCL for short), which is much like your regular experience level (goes from 1 to 27) but is independent of your race and its exp aptitude. Your SCL grows straightforwardly as you gain experience, and it takes 1.3 times as much experience to gain skill cost levels as regular experience levels from the baseline of a 0 exp aptitude race. (The comments mention corresponds to the XL level of a character with 130 exp aptitude in the old aptitude system from a long time ago)

This SCL determines how many experience points it takes to grow a skill by 10 skill points, using the following table:

  Code:

153     const int cost[] = { 1, 2, 3, 4, 5,            // 1-5
 154                          7, 8, 9, 13, 22,         // 6-10
 155                          37, 48, 73, 98, 125,      // 11-15
 156                          145, 170, 190, 212, 225,  // 16-20
 157                          240, 255, 260, 265, 265,  // 21-25
 158                          265, 265 };

Then, whenever you try to train a skill, which happens when you get exp, it will try to allocate experience towards the skills you have set to train in proportion to their listed percentages on the skill training page, as long as there is enough experience in the pool to for every trained skill go up at least 10 skill points at the cost for your current SCL. If there is not enough experience for each skill to train and/or there is still experience left over in the pool, it will then randomly choose skills and train them up at your SCL's cost until the experience in the pool runs out.

From there it goes as the wiki describes it, where you need a certain number of skill points modified by your race's aptitude in that skill to reach the different skill levels.

It looks like most of it is correctly covered in the http://crawl.chaosforge.org/Skills and slightly more hidden http://crawl.chaosforge.org/Skill_point wiki pages. There are some little details not listed, like how exactly it assigns the exp to the different skills, but they do go over pretty much all you would need to know.

[partial]

I don't think it's intuitive that it takes way more goblins to raise your weapon skill to 0 to 1 then it took to raise your fighting skill from 0 to 1 because of the order you chose to raise them in. Knowing that changes my decisions especially when it comes to adding "just a few points" to some off build skills like stealth.

It's pretty common in games for low-level enemies to grant no experience to high level players

[partial]

Would it be possible to at least mention the fact that skills cost most XP with every level? I just looked through the help screen in the skill menu, and there's no mention of this in-game. I can understand the resistance to putting a whole table or graph in the help menu, but something as simple as, "Every level in a skill costs progressively more XP than the previous level," would at least make it clear for crawlers who don't interact much with the online community.

I'd also be a fan of including a single example/rule of thumb, like, "For example, raising a skill from level 20 to 27 requires as much experience as raising a skill from level 0 to 20."

anyone who has ever played a video game should be able to correctly assume that higher skill levels cost more xp to attain