Why I get different values from JS and PHP Mersenne Twister implementations?

Question

1) In PHP when I use native php MT implementation

mt_srand(1); 
var_dump(mt_rand());
var_dump(mt_rand());
var_dump(mt_rand());

I get values

1244335972
15217923
1546885062

2) In this Mersenne Twister implementation http://kingfisher.nfshost.com/sw/twister/
I run

$twister = new twister(1);
var_dump($twister->int31());
var_dump($twister->int31());
var_dump($twister->int31());

and get

1791095845
2135392491
946286476

3) In JS I use
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/VERSIONS/JAVASCRIPT/java-script.html

m = new MersenneTwister(1)
m.genrand_int31()
m.genrand_int31()
m.genrand_int31()

and get

895547922
2141438069
1546885062

How could it happens?

Actually, this in JS

m = new MersenneTwister(1)
m.genrand_int32()
1791095845

and this in PHP

$twister = new twister(1);
var_dump($twister->int32());

return the same value 1791095845, but only for the first call.

Am I missing something? Are you asking why a random number generator is generating random numbers? — Mogsdad
– Mogsdad, Commented Apr 15, 2013 at 17:46

Cairnarvon · Accepted Answer · 2013-04-15 17:50:14Z

4

The Mersenne twister is a class of PRNGs, not a single algorithm. The Mersenne primes used in the algorithm may vary, and different primes will produce different results for the same seeds.

answered Apr 15, 2013 at 17:50

Cairnarvon

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2 Comments

user140827 Over a year ago

So then how can I get equal values for same given seeds on client and on server? Am I should implement MT algo myself?

Cairnarvon Over a year ago

Pretty much. Fortunately, it's not that hard.

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