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(Pseudo) Random Numbers in Javascritp

Anonymous Fri 18 Dec 04:13:20 2020 No.12478724 View Reply Original Report

Quoted By: >>12478773 >>12478924 >>12480651

I'm looking for some tips on how to go beyond the standard Math.random() function in JavaScript to generate random numbers. Does anyone have any practical examples of how to go about this?

Anonymous

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Anonymous Fri 18 Dec 2020 04:17:30 No.12478741 Report

Quoted By:

>javascript
killed the WWW

Anonymous

Anonymous Fri 18 Dec 2020 04:29:02 No.12478771 Report

Quoted By:

Find a source of entropy. Use it.

Anonymous

Anonymous Fri 18 Dec 2020 04:29:44 No.12478773 Report

Quoted By:

>>12478724
Do Math.random() + Math.random()

Anonymous

Anonymous Fri 18 Dec 2020 05:15:51 No.12478864 Report

Quoted By:

incorporate functions that generate variables using real world data like weather or market variables

Anonymous

Anonymous Fri 18 Dec 2020 05:17:01 No.12478865 Report

Quoted By:

Depends, what's the use case?

Anonymous

Anonymous Fri 18 Dec 2020 05:21:46 No.12478878 Report

Quoted By:

You have to beat this guy: https://en.wikipedia.org/wiki/Xoroshiro128%2B

Anonymous

Anonymous Fri 18 Dec 2020 05:38:35 No.12478924 Report

Quoted By: >>12479198

>>12478724
What do you need it for?

Anonymous

Anonymous Fri 18 Dec 2020 07:42:04 No.12479198 Report

Quoted By: >>12479235 >>12479451 >>12480206 >>12480400

>>12478924
Thanks for asking! Needed to shuffle cards for a card game. A common complaint among players of card games involving chance is that the hands dealt don't seem "random enough"; e.g., players will see unlikely combinations appear multiple times during one session of play, which should otherwise be statistically unlikely.

Anonymous

Anonymous Fri 18 Dec 2020 07:57:05 No.12479235 Report

Quoted By: >>12480400 >>12480631

>>12479198
People have bias. You can do statistical tests on the result to see whether it's random or not.
Iirc, JavaScript (at least in Chrome) has very good implementation among mainstream languages, but it can happen that the first few results aren't that good. You should run Math.random() a few times before you use it. Alternatively, try looking at more modern PRNGs like PCG, xoshiro, or Mersenne Twister. I don't know much about JS but you should be able to find libraries for them in npm or github easily.
Do NOT implement your own RNG or mixing two random numbers together to make a "better" random number.

Anonymous

Anonymous Fri 18 Dec 2020 09:30:39 No.12479451 Report

Quoted By: >>12480384

>>12479198
I think this is probably just a manifestation of the birthday paradox. You can suppress it by making the game *less* random, by forcing recognizeable patterns to happen with lower probability than regular.

One example that jumps to mind is the game and watch character in smash brothers. His random number generator never generates the same number within 3 rolls.

Anonymous

Anonymous Fri 18 Dec 2020 14:55:39 No.12480206 Report

Quoted By:

>>12479198
>"random enough"
wtf you'd have to play like a billion games to see a pattern using Math.random()

Anonymous

Anonymous Fri 18 Dec 2020 16:15:40 No.12480384 Report

Quoted By: >>12480400

>>12479451
Agreed, OP your problem won't be helped by finding a more random way to generate numbers

Anonymous

Anonymous Fri 18 Dec 2020 16:23:38 No.12480400 Report

Quoted By:

>>12479198
I agree with these:
>>12480384
>>12479235
It turns out itunes/spotify ran into a similar problem with their playlist shuffling functionality, where random sequences naturally had repeats in songs and people complained that it wasn't random because the same song sometimes played twice or thrice in a row.
I think spotify released a pretty detailed article about how they made their shuffling algorithm less statistically random but more random-looking for humans, so maybe you can use that as a starting point for your own use-case.

Anonymous

Anonymous Fri 18 Dec 2020 17:56:41 No.12480631 Report

Quoted By:

>>12479235
all major JS engines currently use Xorshift128+ seeded with at least 64 bits of system entropy, which is only weak to factoring a huge binary matrix of the least significant bits

Here's some PRNGs you could use

https://github.com/bryc/code/blob/master/jshash/PRNGs.md

or just use window.crypto.getRandomValues

Anonymous

Anonymous Fri 18 Dec 2020 18:02:51 No.12480651 Report

Quoted By:

>>12478724
try the art of computer programming by donald knuth

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