🔒 Locked

Random number generating in PHP & C/C++.

Started by Kanzure Oct 29, 2004 at 9:23 PM 3 replies 1.1k views

Original Post

Oct 29, 2004 at 9:23 PM

I want to create a few demos of an idea I have. The general jist of the idea is to generate content based on random numbers, and saving only the seeds (in my case - time()) so I can recreate the generatables at a whim. I don't have time to write the C/C++ version, so I'm wondering.. is there a way in PHP to generate the same number, with the same seed, as in C or C++? (This way, I can use the same code in my project and not have to rewrite half of the thing.) Thanks. :)

Alex Swinney

Oct 29, 2004 at 10:21 PM

I would say no, but maybe..

If PHP can make the same calls to the same code, then yes. As in, COM..COM is language independent, so if you can get into it you can reproduce the same results from either language. That is, if PHP is able to 'talk' to COM (request an interface).

choffstein

Oct 29, 2004 at 10:26 PM

Look up the Linear Congruence Pseudo Random Number Generator (theory). Identical seeds will produce identical random numbers in most PRNGs, but is guarenteed in this method.

Kanzure

Oct 29, 2004 at 10:27 PM

Possible answers...

MaulingMonkey

Oct 30, 2004 at 9:27 AM

Sorry, but this is a case of RTFM (I'm blunt, deal with it). From php.net:

PHP: rand - Manual
PHP: srand - Manual (seeds rand).

It's built into the language, no need to duplicate it. It's been in there since PHP3 so you SHOULD have it. It auto-seeds by default since 4.2.0, reseed manually and you should have no problem.

To find the first link I entered "rand" in the "search for" field, and left the "in the" field at it's default - "function list". srand was found via link on the rand manual page. Apparently these use the libc implementation.

There is also PHP: mt_rand - Manual (and mt_srand - Manual) which use the Mersenne Twister "which will produce random numbers four times faster than what the average libc rand() provides". (php.net , mt_rand documentation)

[Edited by - MaulingMonkey on October 30, 2004 9:27:46 AM]

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.