Question about the RNG of Maptool

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Altrunchen
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Question about the RNG of Maptool

Post by Altrunchen »

Lately my players have been getting a bizarre amount of critical failures when using XdY roll options and it has me and my ground wondering about the efficacy of the random number generator in Maptool. Currently our record is about 12 nat 1's in one session and the probability of this is astronomical. So I'm wondering if there is something wrong or otherwise about the Maptool RNG. Is this so? If not then is there a way for us to have perhaps more random numbers?
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Jagged
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Re: Question about the RNG of Maptool

Post by Jagged »

Pretty sure its just using Java's random.

ps: in the middle of a session right now, and my players are rolling 1s and I am rolling 20s ;)
Last edited by Jagged on Mon Feb 22, 2016 7:08 pm, edited 1 time in total.

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Altrunchen
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Re: Question about the RNG of Maptool

Post by Altrunchen »

Jagged wrote:Pretty sure its just using Java's random.
So is this really a coincidence then that we get the same result so many times? Does this ubiquity roll option I've seen on the wiki for coding have some advantage over the normal means of rolling as far as random number generation goes?
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aliasmask
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Re: Question about the RNG of Maptool

Post by aliasmask »

You can create your own random numbers by modifying the Wiki: roll() function. But what you're experiencing is normal. For example, you can take a bottoms approach where 1d20 is 21 - 1d20.

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Full Bleed
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Re: Question about the RNG of Maptool

Post by Full Bleed »

Altrunchen wrote:Lately my players have been getting a bizarre amount of critical failures when using XdY roll options and it has me and my ground wondering about the efficacy of the random number generator in Maptool. Currently our record is about 12 nat 1's in one session and the probability of this is astronomical. So I'm wondering if there is something wrong or otherwise about the Maptool RNG. Is this so? If not then is there a way for us to have perhaps more random numbers?
http://forums.rptools.net/viewtopic.php?f=20&t=17423
Maptool is the Millennium Falcon of VTT's -- "She may not look like much, but she's got it where it counts."

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Altrunchen
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Re: Question about the RNG of Maptool

Post by Altrunchen »

aliasmask wrote:You can create your own random numbers by modifying the Wiki: roll() function. But what you're experiencing is normal. For example, you can take a bottoms approach where 1d20 is 21 - 1d20.
Hey there's an idea. I once had an idea where you roll X number of dice and then roll another dice to randomly select which random result came up but something tells me that might not be very effective.
Full Bleed wrote:
Altrunchen wrote:Lately my players have been getting a bizarre amount of critical failures when using XdY roll options and it has me and my ground wondering about the efficacy of the random number generator in Maptool. Currently our record is about 12 nat 1's in one session and the probability of this is astronomical. So I'm wondering if there is something wrong or otherwise about the Maptool RNG. Is this so? If not then is there a way for us to have perhaps more random numbers?
http://forums.rptools.net/viewtopic.php?f=20&t=17423
Oh thanks. Well what do you know? I guess we're just really unlucky.
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Full Bleed
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Re: Question about the RNG of Maptool

Post by Full Bleed »

Altrunchen wrote:I guess we're just really unlucky.
I've been using a "Dice Karma" mod for years that records my player's rolls in MT. And the greatest thing about it is that it allows players to see short term hot and cold streaks... but, without fail, proves a statistical long term average.

In the end, it's not a question of whether or not your rolls will "average" out though... it's all about when you get the high rolls and the low rolls. Players, for example, often don't put as much emphasis on routine skill checks and initiative... getting 20's on them tends to leave very little impression. But the 1's and 20's in combat... those they remember.

Heck, I played a 5e session a couple weeks ago where my 5th level fighter rolled two nat 20's on his inits (we do round by round inits). He also rolled a 1 in combat. But, in all 5 levels, he has yet to *ever* roll a 20 in combat. Not one combat crit in 5 levels. Yet, another player rolled 3 nat 20's on 4 consecutive attacks rolls in the same session. As a result, I jokingly suggested that we institute a socialist "Crit Sharing" rule, where 1 out of every 3 crits should be shared with the less fortunate critters in the group. ;)
Maptool is the Millennium Falcon of VTT's -- "She may not look like much, but she's got it where it counts."

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Re: Question about the RNG of Maptool

Post by metatheurgist »

I know about the many claims that RNG has been tested extensively and shown to produce the correct statistical distribution, not here to debate that.

Our player group has a phrase when Maptool produces ...unusual... results, we say we got "Maptooled", especially when it seems to happen at a moment when an average result would've won the fight but instead we got an ...unusual... result. We've been RPing for decades, many of those years with real dice, we can sense when things are off.

It's not just MT. A long time ago I wrote a program to automate a part of a board game we played extensively. The thought was it would speed the game up (it did) and the experience was greatly improved. But, we all noticed that the RNG that turned up in the program I wrote didn't match the 1000s of rounds of actual battle results we had with the game. Fights that should've been walkovers turned hard, crucial strikes where a reliable average would have meant victory for one often turned into a victory for another, far more often than when we were doing things manually.

Again not saying anything about RNG, just relaying the experience.

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Re: Question about the RNG of Maptool

Post by taustinoc »

metatheurgist wrote:reliable average
A reliable average is evidence of a broken RNG. A reliable trend of any kind is evidence of a broken RNG.

Certainly, there are biased pseudo-random number generators in many programming languages. I recall running across on that had a 20% bias towards even numbers. But that is increasingly rare in modern languages.

The streaks, good or bad, are the memorable ones. I've seen plenty of both. Last Sunday, I saw a player roll nothing over a 2 (on a d10) in a Covert Ops game - with real dice. I've seen literal million-to-one series of rolls, under circumstances where anything else would result in a total party kill - with real dice.

Memory is not a reliable measure of randomness, whether the dice are real or digital, because the human mind is the most powerful pattern matching machine in the known universe. We're so good at seeing patterns, we see them even when they're not there.

All that said, it's possible to implement things in a way that can skew results, but java.security.SecureRandom (which appears to be what's used in MapTool) is considered pretty good. (Though apparently, no pRNG does well if it's initialized too often. I'm guessing the MapTool team knows that.)

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Jagged
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Re: Question about the RNG of Maptool

Post by Jagged »

metatheurgist wrote: we can sense when things are off
You really can't. As others have said, conformational bias naturally leads us to believe the results are broken, yet repeated tracking will show otherwise.

That's not to say Java's random number generator might not be broken. Experience with past random number generators teaches us that seeding mechanisms can be dangerously opaque and esoteric and errors take many years to get spotted. However, I think it extremely unlikely in this case.

If the random number generator was broken, I suspect the most likely thing you would see would be repeating sequences of numbers. However, probably the only way you can comfort your players is to start tracking all d20 rolls.

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Full Bleed
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Re: Question about the RNG of Maptool

Post by Full Bleed »

Jagged wrote:However, probably the only way you can comfort your players is to start tracking all d20 rolls.
Before MT people used to blame their dice... imperfections in the rolling surface... or the pencil on the table that got in the way of the die that was almost certainly going to hit a 20! MT's RNG is just another in a long line of convenient scapegoats. Heck, I can't tell you how many times I've seen players pick up dice and re-roll them after they hit an obstacle that they deemed "invalidated" the result (which is never a nat 20, mind you). I've even considered putting in a random 1 in 20, "bad roll" mechanism in my games that would send a message to players saying something like, "The die bounced off a corn chip on the table and has landed a bit askew on a #. Would you like to re-roll it?" That way they can skew the game a little more in their favor like they would in a regular table-top game. ;) Truth is, with manual die rolling there is always a considerable amount to fudging going on by players (and GM's)... but when you get into the cold world of MT's rng, that skew vanishes and people end up with a more statistically "average" game (provided the sample sizes are large enough).

Remember the player that I mentioned above that got 3 nat 20's in 4 rolls a couple weeks ago (using MT's RNG)? He's one of those guys that swears he's got the worst "luck" in the world and has fumbled more than anyone known to mankind. A year from now he'll still consider himself the unluckiest RPGer alive... and his remarkable string of 20's will have been overshadowed by some "tragic" nat 1 that he throws between now and then at some important juncture in the game. ;)
Maptool is the Millennium Falcon of VTT's -- "She may not look like much, but she's got it where it counts."

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