Re: Portable random number generator

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c,comp.lang.c.moderated,comp.lang.c++

Date:

Thu, 18 Nov 2010 16:22:25 -0600 (CST)

Message-ID:

<clcm-20101118-0017@plethora.net>

On Nov 17, 7:37 pm, Malcolm McLean <malcolm.mcle...@btinternet.com>
wrote:

On Nov 15, 6:56 pm, James Kanze <james.ka...@gmail.com> wrote:

On Nov 12, 11:05 pm, Malcolm McLean <malcolm.mcle...@btinternet.com>
wrote:

On Nov 10, 6:12 am, Gus Gassmann <horand.gassm...@googlemail.com>
wrote:

So now I am looking
for a random number generator with the following properties:
1. Portability.
2. Random starting points.
3. Replicability on demand.

Just use the K and R function
static unsigned long random_seed = 123456;
void simplesrand(unsigned long seed)
{
  random_seed = seed;
}
int simplerand()
{
  random_seed = random_seed * 1103515245 +12345;
  return (unsigned int)(random_seed / 65536) % 32768;
}

Have you actually tried this one? And done any statistical
analysis on the results?

Here are 100 results, created by taking modulus 100 to generate 2
digit integers

[...]

as you can see,

No, I can't see. Pseudo-)randomness isn't superficially
visible. What results do you get from a Chi-Square test, for
example?

they are perfectly OK for many uses, eg random walks for space
invaders, or generating random queries to test a database
function.

They are perfectly OK is you don't care about randomness.

--
James Kanze
--
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