how does luck work in wesnoth?

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quarague
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Joined: September 19th, 2011, 7:35 pm

how does luck work in wesnoth?

Post by quarague » September 19th, 2011, 7:53 pm

I would like to know how exactly the math in the random works, or more accurately confirm or deny my guess of how it works. I looked through the forums and found articles explaining why there is luck in Wesnoth and why people like or dislike it but not how it works.
Let me explain what I mean by an example. If this is not out here and my assumptions are correct I hope this is useful as an example of how to do the computations.
Suppose your unit gets 50% terrain defense and has 3 hits for 6 damage, enemy unit has 40% terrain defense and 2 hits with 8 damage each.
I thought this means you have 3 independent tries to hit each succeeding with 100-40=60% probability and the enemy has 2 with 50% chance of succeeding. We will assume both units have enough hitpoints so that neither of them can die from the attacks. Using some basic finite probability math this would lead to the following:
Enemy suffers 3 hits = 18 damage with 0.6^3=21.6% probability, enemy suffers 2 hits = 12 damage with 3*0.6^2*0.4=43.2% probability, enemy suffers
1 hit=6 damage with 3*0.6*0.4^2=28.8% probability and enemy suffers 0 hits=0 damage with 0.4^3=6.4% probability.
Completely independent of how much damage you dealt your unit will suffer 2 hits=16 damage with 0.5^2=25%, 1 hit=8 damage with 2*0.5*0.5=50% and 0 hits=0 damage with 0.5^2=25% probability.

The reason I wrote this post is that I subjectively feel when I play campaigns against the AI I do not get these probabilities, ie I think the dice are loaded to my disadvantage and I actually do less damage than this example would suggest and suffer more from the enemy.

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averyimaginativename
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Re: how does luck work in wesnoth?

Post by averyimaginativename » September 19th, 2011, 8:03 pm

quarague wrote:The reason I wrote this post is that I subjectively feel when I play campaigns against the AI I do not get these probabilities.
Seeing as this is your first post, I'm going to guess you're fairly new to Wesnoth. Are you aware of the statistics screen?

If you press S, you'll get a table showing your damage inflicted and received and their variation from mathematically expected amounts both for the full campaign and the turn you're playing. Using this, you'll find that (generally) it is just a subjective feeling.

An angry mob will answer the rest of your post shortly :whistle:

[ETA - there was a bug in the stats screen around (I think) 1.9.2. If you get wildly odd %ages it's a bug).
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quarague
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Re: how does luck work in wesnoth?

Post by quarague » September 19th, 2011, 8:47 pm

I wasn't aware of that, thanks. Checking the last two maps I played: damage inflicted -6%, damage taken +2% for the first and -10% and +1% for the second. So it looks like I'm somewhat right :-) I will observe further .

Caphriel
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Re: how does luck work in wesnoth?

Post by Caphriel » September 19th, 2011, 10:27 pm

I thought this means you have 3 independent tries to hit each succeeding with 100-40=60% probability and the enemy has 2 with 50% chance of succeeding.
This is indeed how it works. In your current campaign you've experienced negative inflicted damage overall and slightly positive taken damage overall, but the AI does not "cheat" and mess with the probabilities. Your current results are just a random fluctuation. The last time I played a campaign, I finished with about +25% inflicted and +5% taken :eng:

Velensk
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Re: how does luck work in wesnoth?

Post by Velensk » September 19th, 2011, 10:30 pm

I will note that the stats screen has some inaccuracies, and these inaccuracies will become obvious in any longer campaign.
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WanderingHero
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Re: how does luck work in wesnoth?

Post by WanderingHero » September 20th, 2011, 7:59 am

As far as I can tell, the rng is fair BUT the game uses it so much you will invariably see all attacks hitting or missing and if a mission goes on long enough, theirs always the chance luck will be a ***** and screw you over with an all hit/all miss.


Did you just play HTT? Because the first mission there is HORRIBLE for newbies (weee run away from the horde of enemies while watch your ai allies slowly take their turns) and quite easy to loss due to luck if you try to fight. Start with Orcish Incursion.

Oh and while your starting out, or if you get RNG screwed in an especially ridiculous fashion you could take advantage of the auto save feature... just don't become dependent on it.

MRDNRA
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Re: how does luck work in wesnoth?

Post by MRDNRA » September 20th, 2011, 4:35 pm

I've had some very lucky turns and some very unlucky turns during campaigns, but over time I find they tend to even themselves out. I was actually playing a campaign the other day, got 4/4 hits with one of my units when it was defending with only a 30% chance to hit! On the other hand I've also had 4/4 misses using a red mage (with 70% chance to hit!)

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Felix_Nephthys
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Re: how does luck work in wesnoth?

Post by Felix_Nephthys » September 20th, 2011, 11:50 pm

averyimaginativename wrote:Seeing as this is your first post, I'm going to guess you're fairly new to Wesnoth. Are you aware of the statistics screen?

If you press S, you'll get a table showing your damage inflicted and received and their variation from mathematically expected amounts both for the full campaign and the turn you're playing. Using this, you'll find that (generally) it is just a subjective feeling.

An angry mob will answer the rest of your post shortly :whistle:

[ETA - there was a bug in the stats screen around (I think) 1.9.2. If you get wildly odd %ages it's a bug).
This actually clarified that part of the statistics screen for me. I tried searching the manual and couldn't find anything there and just by luck I happened to come across this thread so thanks.

ayearhasgone
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Re: how does luck work in wesnoth?

Post by ayearhasgone » September 21st, 2011, 10:21 pm

The way luck works is pretty simple-- it simply means your powerful arch mage misses all his shots and a weak enemy unit kills your leader on a castle tile.

Kidding, kidding...

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Aelaris
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Re: how does luck work in wesnoth?

Post by Aelaris » September 26th, 2011, 11:20 pm

Luck is what makes this very different from, say, Chess. In chess, you move a piece, and that will be what happens. In Wesnoth, your units may or may not succeed, and you should plan for both cases.

Perhaps what you perceive as constant bad luck is you taking big chances when you have, say, an overall 70% chance to succeed.

If you have a 70% chance to succeed normally, and a 30% chance to lose horribly, then you're going to remember how one in three times you lost some very valuable unit, while ignoring all the times it didn't happen.

I've seen some people get very whiney, because they feel betrayed when an urfserker with an 80% chance to kill something dies. They feel entitled to victory there, but 80% chance does not make you automatically win. You need a 100% chance (with maniacal laughter) for that. If it's an 80% chance, expect 1 urfserker in 5 to bite it.


Campaigns train this badly, in my opinion, especially if people use savegames to ignore that 1-in-5 chance.
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