# Generating random numbers? **URL:** \ **Category:** ruby-talk\ **Created:** [28 July 2003 21:19 UTC](https://rubytalk.org/t/generating-random-numbers/7068 "2003-07-28T21:19:58Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Harry\_Ohlsen2](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@Harry\_Ohlsen2](https://rubytalk.org/u/Harry_Ohlsen2)\ **Post date:** [28 July 2003 21:19 UTC](https://rubytalk.org/t/generating-random-numbers/7068/1 "2003-07-28T21:19:58Z")
Can someone remind me of the name for the class/method for generating random numbers? I did a quick grep through the library and a google, but all I found was a project that plans to improve the random number generator(s). Thanks in advance, Harry O. ---
**Author:** ![Ben\_Giddings](https://avatars.discourse-cdn.com/v4/letter/b/b19c9b/32.png) [@Ben\_Giddings](https://rubytalk.org/u/Ben_Giddings)\ **Post date:** [28 July 2003 21:27 UTC](https://rubytalk.org/t/generating-random-numbers/7068/2 "2003-07-28T21:27:31Z")
Kernel::rand irb(main):012:0\> rand =\> 0.1986612797 irb(main):013:0\> rand(5) =\> 4 Use the first for a floating point random between 0 and 1, the second for an integer rand between 0 and the number. [http://www.rubycentral.com/book/ref\_m\_kernel.html#Kernel.rand](http://www.rubycentral.com/book/ref_m_kernel.html#Kernel.rand) Ben > **···** > > On Mon July 28 2003 5:19 pm, Harry Ohlsen wrote: > > > Can someone remind me of the name for the class/method for generating random > > numbers? I did a quick grep through the library and a google, but all I > > found was a project that plans to improve the random number generator(s). ---
**Author:** ![Warren\_Brown3](https://avatars.discourse-cdn.com/v4/letter/w/9d8465/32.png) [@Warren\_Brown3](https://rubytalk.org/u/Warren_Brown3)\ **Post date:** [28 July 2003 21:28 UTC](https://rubytalk.org/t/generating-random-numbers/7068/3 "2003-07-28T21:28:31Z")
Harry, > Can someone remind me of the name for the > class/method for generating random numbers? ``` Would you believe....... rand? Kernel#rand takes one optional parameter that if 0 (the default) returns ``` a Float x such that 0 \<= x \< 1, and if not zero, returns an Integer x such that 0 \<= x \<= parameter. Use Kernel#srand to seed the random number generator. ``` I hope this helps! - Warren Brown ``` ---
**Author:** ![Brandon\_D\_Valentine](https://avatars.discourse-cdn.com/v4/letter/b/a6a055/32.png) [@Brandon\_D\_Valentine](https://rubytalk.org/u/Brandon_D_Valentine)\ **Post date:** [28 July 2003 21:31 UTC](https://rubytalk.org/t/generating-random-numbers/7068/4 "2003-07-28T21:31:34Z")
Kernel::rand Seed it via: Kernel::srand HTH, Brandon D. Valentine > **···** > > On Tue, Jul 29, 2003 at 06:19:58AM +0900, Harry Ohlsen wrote: > > > Can someone remind me of the name for the class/method for generating random > > numbers? I did a quick grep through the library and a google, but all I > > found was a project that plans to improve the random number generator(s). > > – > [brandon@dvalentine.com](mailto:brandon@dvalentine.com)[http://www.geekpunk.net](http://www.geekpunk.net) > Pseudo-Random Googlism: texas is the reason do you know who you are? ---
**Author:** ![Cedric\_Foll1](https://avatars.discourse-cdn.com/v4/letter/c/e95f7d/32.png) [@Cedric\_Foll1](https://rubytalk.org/u/Cedric_Foll1)\ **Post date:** [30 July 2003 02:24 UTC](https://rubytalk.org/t/generating-random-numbers/7068/5 "2003-07-30T02:24:14Z")
Harry Ohlsen wrote: > Can someone remind me of the name for the class/method for generating random > numbers? I did a quick grep through the library and a google, but all I > found was a project that plans to improve the random number generator(s). > > Thanks in advance, > > Harry O. oban:~# irb irb(main):001:0\> rand(10) =\> 8 You have the rand method. rand(n) return a number in [1…n-1]. ---
**Author:** ![Josef\_Jupp\_SCHUGT](https://avatars.discourse-cdn.com/v4/letter/j/7ba0ec/32.png) [@Josef\_Jupp\_SCHUGT](https://rubytalk.org/u/Josef_Jupp_SCHUGT)\ **Post date:** [30 July 2003 20:28 UTC](https://rubytalk.org/t/generating-random-numbers/7068/6 "2003-07-30T20:28:44Z")
Saluton! - Harry Ohlsen; 2003-07-28, 21:35 UTC: > Can someone remind me of the name for the class/method for > generating random numbers? Nobody did ask this so far: What kind of random numbers do you need and for what purpose. Ruby’s RNG may be nice for Monte Carlo simulations (because it has a very large period) but it is NOT SECURE for CRYPTOGRAPHY as it is. You may wish to visit [http://www.math.keio.ac.jp/matumoto/emt.html](http://www.math.keio.ac.jp/matumoto/emt.html) Gis, Josef ‘Jupp’ Schugt > **···** > > – > N’attribuez jamais à la malice ce que l’incompétence explique ! > – Napoléon ---
**Author:** ![Harry\_Ohlsen2](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@Harry\_Ohlsen2](https://rubytalk.org/u/Harry_Ohlsen2)\ **Post date:** [28 July 2003 21:43 UTC](https://rubytalk.org/t/generating-random-numbers/7068/7 "2003-07-28T21:43:38Z")
Thanks! > **···** > > On Tue, 29 Jul 2003 07:28, Warren Brown wrote: > > > Harry, > > > > > Can someone remind me of the name for the > > > class/method for generating random numbers? > > > > ``` > > Would you believe....... rand? > > > > Kernel#rand takes one optional parameter that if 0 (the default) > > > > ``` > > > > returns a Float x such that 0 \<= x \< 1, and if not zero, returns an Integer > > x such that 0 \<= x \<= parameter. Use Kernel#srand to seed the random > > number generator. > > > > ``` > > I hope this helps! > > > > ``` ---
**Author:** ![Harry\_Ohlsen2](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@Harry\_Ohlsen2](https://rubytalk.org/u/Harry_Ohlsen2)\ **Post date:** [30 July 2003 20:59 UTC](https://rubytalk.org/t/generating-random-numbers/7068/8 "2003-07-30T20:59:10Z")
> Saluton! > > - Harry Ohlsen; 2003-07-28, 21:35 UTC: > > > Can someone remind me of the name for the class/method for > > generating random numbers? > > Nobody did ask this so far: What kind of random numbers do you need > and for what purpose. That’s a good question. I’m no statistics guru, so I probably don’t really know :-). However, I’m guessing that uniformly distributed is probably fine, which I think is what rand() tries to generate. What I’m using them for is to try to find a generator in Z\_n. I plan to do some experimentation to see whether doing it that way (there’s a little more to the approach, but it’s basically random) compared to using brute force (ie, checking the order of 2, 3, … until we find one that’s phi(n)). > Ruby’s RNG may be nice for Monte Carlo simulations (because it has a > very large period) but it is NOT SECURE for CRYPTOGRAPHY as it is. Thanks. It might be good for my experiment. I’ll take a look. Harry O. > **···** > > On Thu, 31 Jul 2003 06:28, Josef ‘Jupp’ Schugt wrote: ---
**Author:** ![Paul9](https://avatars.discourse-cdn.com/v4/letter/p/9fc29f/32.png) [@Paul9](https://rubytalk.org/u/Paul9)\ **Post date:** [31 July 2003 17:42 UTC](https://rubytalk.org/t/generating-random-numbers/7068/9 "2003-07-31T17:42:15Z")
> Saluton! \* Harry Ohlsen; 2003-07-28, 21:35 UTC: > > > Can someone remind me of the name for the class/method for > > generating random numbers? ``` > Nobody did ask this so far: What kind of random numbers do you > need and for what purpose. > Ruby's RNG may be nice for Monte Carlo simulations (because it > has a very large period) but it is NOT SECURE for CRYPTOGRAPHY > as it is. You may wish to visit > http://www.math.keio.ac.jp/matumoto/emt.html > Gis, > Josef 'Jupp' Schugt -- N'attribuez jamais à la malice ce que > l'incompétence explique ! -- Napoléon ``` Actually, Ruby’s RNG isn’t so great for Monte Carlo or discrete event simulations. I’d only use it for games. The problem isn’t the quality of the generator (I think Matz is using the Mersenne twister algorithm). It’s that “randomness” is obtained by a method rather than a Random class which can instantiate Random objects. If there were separate random objects, each of which maintained its own seed state, it would be much easier to create designed experiments with common or antithetic random variates which you could exploit for variance reduction. Having a method restricts you to a single stream of randomness unless you’re willing to go through contortions. –paul