this post was submitted on 02 Feb 2024
22 points (100.0% liked)

Programming

17668 readers
150 users here now

Welcome to the main community in programming.dev! Feel free to post anything relating to programming here!

Cross posting is strongly encouraged in the instance. If you feel your post or another person's post makes sense in another community cross post into it.

Hope you enjoy the instance!

Rules

Rules

  • Follow the programming.dev instance rules
  • Keep content related to programming in some way
  • If you're posting long videos try to add in some form of tldr for those who don't want to watch videos

Wormhole

Follow the wormhole through a path of communities !webdev@programming.dev



founded 2 years ago
MODERATORS
 

Hi all,

Some time ago I've been thinking about a programming challenge that's not simply another HackerRank style algorithm task and came up with something that I myself had a lot of fun solving. It goes like this:

We have a well known function (as in I didn't come up with it):

 function xoshiro128ss(a, b, c, d) {
                return function() {
                    var t = b << 9, r = b * 5; r = (r << 7 | r >>> 25) * 9;
                    c ^= a; 
                    d ^= b;
                    b ^= c; 
                    a ^= d; 
                    c ^= t;
                    d = d << 11 | d >>> 21;
                    
                    return (r >>> 0) / 4294967296;
                }
            }  

We initialize it with 4 random parameters a,b,c,d (that I selected) :

  let rnd = xoshiro128ss(a, b, c, d);

and we do:

  let rand1 = rnd();
  let rand2 = rnd();
  let rand3 = rnd();
  let rand4 = rnd();

Knowing that:

rand1 == 0.38203435111790895
rand2 == 0.5012949781958014
rand3 == 0.5278898433316499
rand4 == 0.5114834443666041

What are the values of a,b,c and d?

I was wandering if it's possible to figure it out and couldn't stop trying until I did. It was an interesting journey and I learned some new things along the way Maybe someone else here will also have fun with it. As for prizes, I don't know... whoever posts the right answer first gets an upvote and eternal fame.

you are viewing a single comment's thread
view the rest of the comments
[–] ExLisper@linux.community 5 points 10 months ago

Not a lot of math in this one. At least not in the way I did it.