The second iteration of 2v8 is now LIVE - find out more information here: https://forums.bhvr.com/dead-by-daylight/kb/articles/480-2v8-developer-update

Survivor escape rates vs killer win rates, a bit of math to understand why the devs are right.

drsoontm
drsoontm Member Posts: 4,903
edited November 8 in General Discussions

edit: To make this a bit more fun. I've written an app in javascript so anyone can play with the escape rate in a graphical environment.

The app is at: http://www.drsoon.xyz

— Original post —

It shouldn't be so difficult to grasp, but apparently it is.

Here are the measured escape rates offered by BHVR:

These are averages.

In essence, the mean escape rates varies between 40% and 48%

These past few days, many posts have questioned the rates, completely ignoring the past of the game.

Maybe this will help them think a bit.

A killer wins when he sacrifices more than two survivors. The draw and loss are implicitly 2 kills and less than two kills.

What does these rates mean in practice for the killer?

A 40% mean escape rate means the killer will win about 47% of the time.

A 48% mean escape rate means the killer will win about 34% of the time. Yes, in high MMR, against an SWF killers lose about two third of their matches.

You don't believe me? Simulate it!

The following python* code plays many matches and escapes survivors with the given mean escape rate.

It counts the escapes per matches and then computes the killer wins, losses and draws.

#!/usr/bin/python
# by yours truly, drsoontm
import random
import sys

DEFAULT_RATE = 40
SIMULATION_COUNT = 100000

SURVIVOR_COUNT = 4
DRAW = SURVIVOR_COUNT / 2


def dbdsimulate(rate, simulation_count, as_csv):
    killer_wins = 0
    killer_losses = 0

    for j  in range(0, simulation_count):
        escape_count = 0
        for i in range(0, SURVIVOR_COUNT):
            escaped = random.uniform(0, 100) <= rate
            if escaped:
                escape_count += 1
        if escape_count > DRAW:
            killer_losses += 1
        elif escape_count < DRAW:
            killer_wins += 1

    wr = (100.0 * killer_wins) / simulation_count
    lr = (100.0 * killer_losses) / simulation_count
    dr = 100.0 - (wr + lr)
    if as_csv:
        print(f"{rate};{wr:.2f};{lr:.2f};{dr:.2f}")
    else:
        print(f"r: {rate}% w: {wr:.2f}% l: {lr:.2f}% d: {dr:.2f}%")


def main():
    rate = DEFAULT_RATE
    as_csv = False

    for arg in sys.argv[1:]:
        if arg == '--csv':
            as_csv = True
        else:
            try:
                rate = int(arg)
                if not 0 <= rate <= 100:
                    print(f"{arg} isn't in [0; 100] and isn't --csv")
                    sys.exit(1)
            except ValueError:
                print(f"{arg} isn't an integer and isn't --csv")
                sys.exit(2)

    dbdsimulate(rate, SIMULATION_COUNT, as_csv)


if __name__ == '__main__':
    main()

The program can accept an escape rate in [0;100] and —csv (dash dash c s v).

By default the escape rate is set to 40

Given the csv option, one can also look at the measured distribution:

edit: red: killer win rate, blue: survivor escape rate

All in all, the "power role" (in the theme) only wins about half the time, which mean, as a team, survivors win about half the time too, on average, overall.

I'm also surprised to note that killers really tend to lose way more than survivors as a team at high MMR (against SWF4).

This should make very clear the balancing of the game is way better, overall, that what even the most reasonable among us think.

*python is the new basic. Even non-programmers can try it online (e.g. https://www.online-python.com/)

Post edited by drsoontm on
«1

Comments

  • danielmaster87
    danielmaster87 Member Posts: 9,440

    I always appreciate someone doing the math on the game. This proves the devs "right," but it doesn't mean it's a good goal to set. Even if the 60% kill rate is true, that still means that killer gets little more than a draw most of the time. And possibly, if we look at all match combinations that could lead to that average, a killer could draw like 80% of their matches, and still "win more than the lose" to get that 60%. That, to me, doesn't seem like a good outlook on the role, and doesn't encourage anyone to play it. I know survivors must escape as well sometimes, but you are a "killer," not a "chaser" or a "pallet breaker."

    The kill rate and escape rate doesn't mean anything as long as the game is balanced around skilled play, but that's a separate discussion.

  • GeneralV
    GeneralV Member Posts: 11,326

    I'm glad to help, friend.

    …I still don't understand, but that is okay, friend.

    Anything that even remotely involves math is extremely difficult for me.

  • smurf
    smurf Member Posts: 348

    OP's approach is a good start, and what you say is also very true. I deal with a lot of identification of trends and understanding correlations and statistics in my job, and I fully agree that going next on hook, friendly killers, and other influences need to be accounted for to better understand what's really happening in people's games.

    I'm a novice at Python, so I probably won't run through the code unless I get super curious. But these factors could be coded into a simulation also. Accounting for the randomness of some of the variables you discussed is feasible, but the accuracy of the resulting model can always be questioned until it's inputs and outputs are verified against known quantities.

    So yeah, OP: well done!

    This comment: good point!

  • rysm
    rysm Member Posts: 272

    We stan a Python king/queen/monarch. Lovely post OP. I see a lot of people still aren't happy (it is the DBD community after all lol). But thank you for the effort and explanations. They are very much appreciated.

  • AMOGUS
    AMOGUS Member Posts: 489

    People typically give up and throw themselves at the hook, I deal with people like that Nea that LilithOmen posted a lot more. People refusing to wiggle in my arms, I know they're going to kill themselves the moment I hook them… I just slug them if I sense they're throwing a tantrum.

    TBH, I play at mid MMR and I have noticed this being a thing, Survivor mentality nowadays is really bad, and strong Killer play just makes people give up, even if it's 2 gens left and nobody is dead. It's frequently not because of "Knock Out" or "muh Blight!!!1", it's just pure "Waaah, I'm not winning!".

  • Spare_Them_Mori_Me
    Spare_Them_Mori_Me Member Posts: 1,679

    Well, curious how this plays out. I always wondered why draws were never talked about.

  • Raptorrotas
    Raptorrotas Member Posts: 3,249

    SIIm always curious about how people call out some math fallacy then proceed to present survivors being able to draw with the killer.

    Killer winrate + draw + survivor winrate = 1 doesnt exist in dbd. It's killrate + escape rate = 1... which only indirectly has anything to do with the win rates.

    There's only one out of five outcomes of a trial in which no survivor wins. And thats the 4k.

    • survivor A wins when A escapes
    • survivor B wins when B escapes
    • survivor C wins when C escapes
    • survivor D wins when D escapes
    • The killer wins if more survivors die than escape (3-4k)

    BBut then people also get the following stuck in their head, even though its not enforced or hinted at ingame:

    • "The survivor team" wins if there are more escapes than kills
    • The "draw" happens on a 2k because kills equal escapes.

    SSo now we have the problem that the killer win is in direct comparison to two different variables, the individual winrate and the team winrate. So which one of the two should be equal the killers?

    IIf you go for an 50% average escape chance, the team wins ~31%, the killer wins ~31% and the rest is draws. But is it really fair for every survivor to have a ~1,6times higher chance to win than the killer?

  • PreorderBonus
    PreorderBonus Member Posts: 321

    You're mistaken. A Killer 'winning' doesn’t mean Survivors are 'losing.' Both the Killer and Survivors can win simultaneously in a match, so when there’s a draw, two Survivors also 'draw.' A 2K is the same as a 2E. The only scenarios where only one side wins are a 4K or 4E. So attributing all 2Ks as Killer wins and Survivor losses is inaccurate.

    • 0k (or 4e): Clear survivor win.
    • 1K (or 3e): Survivor-favored outcome.
    • 2k (or 2e): Neither side exclusively "wins." Both could consider this an acceptable or neutral outcome.
    • 3k (or 1e): Killer-favored outcome.
    • 4k (or 0e): Clear killer win.

    This leaves us with 2 possible win scenarios for the survivor side, 2 possible win scenarios for the killer side, and 1 scenario where both sides win equally. You're making it seem like 2k/2e is favoring the Killer when it's not.

    Then you'd have to consider that the players using Nightlight are just a tiny fraction of the community and not representative of the actual stats of the game. According to the official data, Survivors escape around 43.5% of matches, aligning closely with the 40% escape rate (or 60% kill rate) that BHVR is targeting.

    But ultimately, debating escape rates is pointless because many Survivors aren’t necessarily playing to escape. Plenty are focused on completing rift challenges, goofing around with friends, being overly altruistic, testing new builds, and so on. Without a dedicated "ranked" mode where everyone plays with the intent to escape, these stats are just one factor among many others, and trying to boil down the game’s balance to them alone is ignorant.

  • Toystory3Monkey
    Toystory3Monkey Member Posts: 830

    all this stuff also doesnt account the match dynamics.

    killer can lose miserably and win over single moment because the game actually allows killer to bypass their intermediate objective and get straight to the kills. For example by getting noed snowball or simply having survivors throw the game at last gen bc they got too greedy.

    survivors can have a lot of inherent advantage, but simply make a big enough mistake and lose the whole game to it irreversibly as it snowballs and goes out of control.

    killer in the meantime is a mistake punisher role that certainly can seriously tank their ways to win by making mistakes or not being powerful enough, but still have a chance to snowball at any moment.

    survivors only get the mechanic that skips their objective when 3/4 are dead.

    it doesnt make much sense trying to compare win cons of either sides and try to balance for them because they're inherently incomparable

  • AmpersandUnderscore
    AmpersandUnderscore Member Posts: 1,808

    I address draws here, that's what a 2k is.

    Since you didn't read it, let me parse it for you:

    Just defining a killer win to be a 3k or 4k pts killers winning about 51% of the time, and draws occur about 12.5%. so survivors are winning about 37% of the time

  • DeBecker
    DeBecker Member Posts: 281

    why pushing survival rate against win rate? Its not even the same ground.

  • RpTheHotrod
    RpTheHotrod Member Posts: 1,933

    It's not 1 to 1 though. A 40% escape rate is per survivor, and there are 4 survivors in a match. You can still lose (you got sacrificed so your escape rate went down) but the other 3 survivors win resulting in a killer loss.

  • drsoontm
    drsoontm Member Posts: 4,903

    That's not the point. The point is that there have been many discussions questioning the target escape rate.

    This script (and now the app in http://www.drsoon.xyz ) shows a good reason for that choice.

    What assumptions?

    The chosen default escape rate is provided by BHVR a.ka the most accurate data we can have.

    But more t than that, it's also the target chosen by BHVR. (40% escape rate, 60% kills).

    It appears you misunderstand the use of the random uniform. A 40% escape rate means that, on average, a survivor escapes 40% of the time. So the program draws a random number between 0 and 100 (and it quite obviously need to be uniform) for each of the four survivors to determines if it has escaped or not. That's quite trivial.

    As for the killer win, that's has always been defined like that: 2 kills: a draw, more a win, less a loss. But I'm not working on the survivor team wins, only the escape rate. Note that draws are irrelevant as they are just a "meh" game for both sides.

    I'm convinced you don't understand what the program does and I don't know how to help you.

    I'm not talking about the survivor team win rate. I've been very careful speaking about killer wins and survivor escapes.

    The whole discussion that pushed for this is all these posters complaining about the 40% escape rate being too low.

    The "throwing a bone" you are talking about is part of that target 40% escape rate. That's how BHVR is quite skilfully on that 40% target.

    In this case because a draw seems quite irrelevant. Neither side has won, two survivors are sacrificed. That's a "meh" on both sides.

    The program only shows, by simulation, why the 40% target from BHVR makes perfect sense.

    Everything else is out of scope.

    A 60% escape rate would translate to about a 18% win rate for the killer. Nobody would play killer ever (people were already leaving in droves with a 50% escape rate)

    You started well understanding the way computations are made (as simply as I could so anybody could understand …)

    Yet you fail to understand what the program does.

    You understand that it decides if a survivor escapes by rolling a dice. Right?

    So you can understand that doing that for four survivors decide if the match is a win (a.k.a more than two kills) for the killer.

    Additionally, I'm assuming you understand the convergence of results for truly random sampling (of which uniform random is a decent approximation)

    So if you understand all that then you have to understand the result is accurate. (I'm hoping you understand the difference between survivor escape rate and survivor team wins.)

    Do it yourself if you want, you'll get the same results.

    As for the arguments about players ruining matches not being counted, it's obviously the one thing to do and … it doesn't even matter.

    All the program says is that a 40% escape rate gives about 47% win rate for the killer.

    The reason survivors escape at 40% is utterly irrelevant.

    The points remains: BHVR targets 40% and, from their own accurate measure, get these results when players aren't rage-quitting.

    People have complained about that 40% target and this shows 40% is only giving a 47% win rate for a killer.

    Everything else is a moot point.

  • SharonPancakes
    SharonPancakes Member Posts: 15

    Stats are old, all you have to do is play the game to see the devs aren't right about anything honestly lol.

  • drsoontm
    drsoontm Member Posts: 4,903

    The stats are only used for the default value of the escape rate. (Besides, from a recent post from a dev/modo (can't recall the name: too tired), the current stats are not significantly different from these.)

    You give the program an escape rate and you see how it translates in term of killer win. That's all it does.

    I wrote it because of the complains about the 40% escape rate target (a.k.a 60% kill rate target)

    (If you look at the top, there is a web app to toy with the numbers)

  • TheSubstitute
    TheSubstitute Member Posts: 2,495

    Isn't the issue more that your program assigns a comparable weight to each survivor escaping and doesn't reflect that once a survivor dies the chance for the remaining survivors to also escape is less than 40% so the weighting is inaccurate?

    I'm just asking for curiousity by the way. I'm fine with the target escape rate being 40%; I just want the game to be fun by making game mechanics favour spreading hooks so the game is more enjoyable. However, I'm not invested in what the escape rate is as long as the game is fun to play for both roles.

  • TheSubstitute
    TheSubstitute Member Posts: 2,495

    That's interesting. That correlates with how when I recorded my most recent set of 100 survivor matches I saw that a 4K result was 2.5 times more likely than a 4E result.

  • drsoontm
    drsoontm Member Posts: 4,903

    It's a good question.

    The data from BHVR says each survivor has a 40% chance of escaping on average, no in-game condition attached.

    On the web app, I draw the actual mean escape rate of the survivors (in blue). It converges close to the chosen rate.

    The way I see it, the reason survivors have escaped isn't really relevant, only that they have escaped at a rate close to that specified value. And of course the main information is the deduced killer win rate for said value.

    I've given the program so people could play with it "refuse to share the value". Conspiracy theorist much?

    The draws are irrelevant as they mean that both teams have got a null.

    "proven wrong" then proceeds speaking about something I've specifically said was irrelevant.

    I don't believe you understand what this is about.

  • Autharia
    Autharia Member Posts: 383
    edited November 9

    The simulation also doesn't take in any current tactics of the game or skill of players its just a random roll generator. So of course it will keep the hard 40% floor escape rate no mater what. It is just like the dps simulators of RPG games to sim gear 99% of the time it takes in an unplayable skill level and imposable circumstances for the numbers it puts out.

  • Vishlumbra
    Vishlumbra Member Posts: 162
    edited November 9

    I ain’t no math expert, but, the simplest way of looking at it is that each survivor has a 40% chance of escaping, there’s four of those. Killer to win the match needs to surpass the odds of a 40% escaping survivor, 3 times.

    Just saying that the 60/40 is not the end of all things. There’s a bunch of factors you have to consider:


    1 - Each individual survivor has a 40% chance of escaping, which means that to achieve a “win” the killer has to beat those 40% odds three times.

    2- Killers are vastly different in strength, survivors can be considered equal because there’s no real difference. So top meta Killers could be carrying weaker killers, which in return could be having horrible games.

    Saying that survivors should have a 50% chance of escaping would make the already hard role of playing killer, way harder, because it’s not a 1vs1, it’s a 1vs4 and basically you need 3 to win.

  • drsoontm
    drsoontm Member Posts: 4,903
    edited November 14

    What are you even talking about. There is only one information available about the kills and it's 60%, from where are you pulling that gaussian? Try to be more explicit.

    I believe you are correct. And I should never use the word "math", it makes it looks way more complicated than what it is.

    It's all about the perception of the game.

    Killer wins are defined as seen above. (I'm too tired to repeat all that)

    Survivors (plural) win should naturally be the opposite but in practice it isn't. The vast majority of survivors only focus on their own escape: survivor (singular) win. Hence that regular ranting about 60% kill rate. That's why I looked at the win the way they are perceived.

    But one of the points is that 50% gives a very low rate of win for the killer, which may explain why a while ago when the kill rate was balance for 50% survivor queues went up: it was high-mmr even at the basic killer level.

    Draws are irrelevant because they are not a win. I'm not sure in English but in French it's called a "mach nul", one meaning being "the same as if it never happened" (nul et non avenu). They dont really have an equivalent for singular survivor wins as it's kind of all of nothing on that front. Nothing really interesting to take from that.

    Yes, I've seen the 17% too, which is interesting, or would be if survivors cared that much about team wins. It's all about perception. (And I realize I've not updated the web app to also draw that curve, I'll do it if I recall tomorrow.)

    We keep speaking about 40% escape rate mind you but the 48% escape rate in high MMR is also intersting (and explains why that level of play can be so frustrating). I know this detail doesn't escapes you and you expect it to be like that, as do I.

    I see everything as system, that aside you may have a point directly in relation with mine. Let me think …

    Yes, you are right. Hatch escapes are inflating the escape rate somewhat. Win perception on the survivor side may be lower than projected because of that. I'd love to be able to discriminate them out. There is no data about this though. If you can find some BHVR stat about hatch escapes, I'd love to try to include them.

    47/37 I presume you are talking about the measured win rate results of the matches. It's about perception here again. I understand not everybody sees it like that but, for me, if it's not a win, its a loss (I guess I'm extremely competitive).

    I fully agree opinion may diverge about this. I've simply provided a tool to have a better idea of what these statistics mean.

    If other people draw different conclusions than mine and don't see why I'm only focused on win, it's all the same to me. (Once I believe I've explained myself sufficiently, and I believe I did.)

    Opinions are subjective after all. I'd not call either of them biased though.

    I'm perfectly happy with my survivor escape rate (about 60%*) and killer kill rate (about … a lot, I don't dare to say how high, with my main**), neither of which are matching these stats. But as you probably know, personal observations are hardly representative.

    *) and I consider myself pretty average: it's mostly luck and stealth.

    **) Nurse, relatively decent at it if I say so myself.