Minigawa Discusses Our Lack Of Faith In The RNG Gods

28 Jul 2014


Have you ever had the thought that the randomness that occurs while gathering or crafting isn’t random at all? That in fact, the entire system is working against you because you’ve failed your last few 90%+ synths?

Did you know there’s a reason why you think that?

Hiroshi Minigawa has dropped a knowledge bomb on the forums explaining why that is.

Hiroshi_Minagawa's AvatarHello,

Since this was brought up in the UI forum, even though I’m not in charge of it I will go ahead and comment about this a general discussion point.

I checked up with our main programmer “K”, and for FFXIV it seems like we are using 3 famous random algorithms different depending on the application. Naturally, everything is processed server-side, and the random seed differs for each process.

So in response to the question if there is a bug with the coding that generates the same random number if you continuously press an action, the answer is that the system implemented is such that this type of problem will not occur.

There were older games where you could use certain patterns to your advantage to beat the game, but in recent days there aren’t any games like this anymore. Probably.

However, the rate (random) process in games from very long ago and up until now — not only for FFXIV — have continued to be doubted by players.

From my perspective it’s just a clear cut case of chance, but this alone may not be convincing enough, so I will try to explain about this a bit.

This discussion is not particular to FFXIV and it is more about why random number programs are easily doubted.
(Of course there have been a number of cases where there were bugs…)

So to start off, I’ll lay out the essential points quickly.

A. The standard random number programs used by FFXIV, and other modern games, generate practical “true random numbers”.

B. With a range of trial numbers that can be understood by a person, because it’s a true random number bias arises.

C. Since our brains are very adept in their capability to detect bias as abnormal or a singularity, we perceive true random numbers as abnormal.

I’ll explain about each point above individually.

First, I’ll start with the program for generating random numbers.

FFXIV and other modern games use a random number algorithm (properly known as a pseudorandom number generator), which was contrived by some really good mathematicians and computer science people, and it was tested for a number of fields and is used as a solid algorithm.

As an example, I’ll explain a little snippet about the periodicity of the random number algorithm known as Mersenne twister.
“The algorithm provides a super astronomical period of 2^19937 – 1 and 623 dimensional equidistribution up to 32 bits accuracy.”

Got it? No? That’s okay.

Random number algorithms are part of a field that was built by the results of pure mathematics. As long as we the users understand that the random numbers generated are correct and practical that is more than enough.

★Those of you who know about random number algorithms and examples of problems in the past that arose in games, you’re probably wondering about something I didn’t touch on above. I will add an explanation to the end of this post.

Next is about “true random numbers”.

When it comes to random numbers there are two different types with different distribution patterns: uniform random numbers and normal random numbers. As the number of trials increase, we start to converge on the ideal condition.

Conversely, if the number of trials (sampling number) is low, bias arises in random numbers.

As humans, when it comes to the number of trials in games and such that we are able to grasp, it’s normal for us to perceive bias in the random numbers.

In other words, the premise that it’s strange that there is bias in random numbers is mistaken.

Of course, with hundreds and thousands or billions of trials, we will approach a distribution that is uniformly random and the bias will disappear. Unfortunately, this is impossible for a human to actually observe and experience.

Due to this, every time you observe bias arising from a limited number of trials you can’t help but think that something’s wrong.

Finally, onto our cognitive fallacies.

Humans are able to instantly determine and intuit various things. It’s often said that our brains are really good at this but computers have trouble. On the other hand though, there is an aspect to this ability that is weak, and when this is exploited it opens us up to tricks and deceit.

The pattern of deviation in judgment and illogical interpretation is known as cognitive bias.

A leading example of where cognitive bias arises is the Gambler’s fallacy.

This states that when a person observes multiple events over the course of time, they will begin to expect that the results in the future will be affected by what happened in the past, and will either feel convinced that the results were due to a cause-and-effect relationship, or have a feeling of strangeness.

When you flip a coin 5 times in a row, the rate in which you land either heads or tails for the 6th flip will be 50%. However, our gut feeling says “this time for sure!” and we modify this with an expected value, and as a result when it lands heads we think “No way!” or when it lands tails we think “Just as I thought!” This is cognitive bias.

As I stated in b) above, the feeling that something is strange even though it is not is our brains are trying to create a cause-and-effect relationship that we anticipate, but the rate behaves in a completely unrelated manner.

(I’m writing this in a definitive matter, but please be aware that I am regurgitating what I read from a book.)

Cognitive bias is similar to a bug in humans’ cognitive capability, but it seems like it’s a system that was acquired for our survival to decide things efficiently in times of emergency.

The whole topic of cognitive bias is really fascinating, so if you are interested I recommend reading
this book.

This pretty much sums up why we often think something is up with the probability we encounter in games.

Bonus info: An aspect I didn’t touch on earlier in regards to random number algorithms.

Amongst the random number algorithms, one method that is often adopted that has a high cost to efficiency ratio is the linear congruential method; however, it’s well known by implementers that there is an issue where large bias arises.

In fact, there was a game that mistook the use of this function, and as the sample size grew larger the more bias increased. Meaning that just because it’s a well-known method doesn’t necessarily mean that it’s proof of it being accurate.

Additionally, even if a random number sequence is generated properly, depending on how the application uses this value, ultimately there may be cases where strange patterns arise.

So with all of this said, this is not one big post about the evidence of the accuracy of XIV’s various probability calculations. As I mentioned that the beginning of this post, the latter portion of this long comment is mainly just chitchat, but in response to the question as to whether there is something wrong with the probability in XIV, the answer is no, there is nothing wrong.