And yet another random number generator library (was posted at were-
here.com a long long time ago). All open source, credit for use is
nice though. :)
This one is a linear congruential generator. I've never tested the
output against anything, so at best, this may or may not work
properly for your needs.
cheers,
jon
Jon Bradley
VFX Artist / Animator
Post Central, Inc.
[EMAIL PROTECTED]
www.cherrycrushthemovie.com
/** BEGIN LCG.as */
/**
* Class com.jbradley.math.LCG
* Author Jon Bradley
* Version 1.0
* Description Implementation of 48-bit Linear Congruential Pseudo-
Random Number Generator
*
------------------------------------------------------------------------
-------------------
* Last update: November 3, 2005 - Converted to AS 2.0
*
------------------------------------------------------------------------
-------------------
* 48-bit Linear Congruential Algorithm
* Produces pseudo-random number which can be seeded manually or by a
default time variable.
*
* Source: Computational Nuclear Physics Group, United States Government
* RNG - Random Number Generator algorithms
*
* This implementation is limited to the 48-bit version, which is
still computationally
* inaccurate in Flash due to a 32-bit limitation. It is also not
statistically a sound
* random number generator due to patterns in the low order sequences
and is not a
* cryptographically secure algorithm. It can be made secure by using
a cryptographic hash
* function to generate an initial random number state from a pair of
integers (keys).
*
* The algorithm implementation is as described in the RNG library
published by the
* Lawrence Livermore National Laboratory - http://nuclear.llnl.gov/
CNP/rng/rngman/
*
* Converted to Actionscript by Jon Bradley, 2003
*
------------------------------------------------------------------------
-------------------
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
are met:
*
* - Redistributions of source code must retain the above
copyright notice,
* this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
copyright
* notice, this list of conditions and the following disclaimer
in the
* documentation and/or other materials provided with the
distribution.
*
* - Neither the name of this software nor the names of its
contributors
* may be used to endorse or promote products derived from this
software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
------------------------------------------------------------------------
-------------------
*
* Usage:
*
* Default:
* rGen = new LCG();
*
* Specific seed - may use new Date.getTime() ):
* rGen = new LCG( 1000000000000 );
*
* Methods:
*
* init(t:Number)
* Initializes LCG with a time seed. If t is not supplied or
* is NaN, default is used.
*
* getSeed():Number
* Returns initial time seed used to start the system. Recall
that the actual seed
* used in the algorithm is time&M, where M is 2.8^14. The
returned number maybe
* be passed back in to init to restart the random sequence:
*
* rGen.init( rgen.getSeed() ) // Will restart system
with original seed
* rGen.init() // Will restart system
with new seed
*
* random()
* Shortcut method to randomReal48()
*
* randomReal48()
* Returns a random 48-bit floating point number on interval
[0,1).
* Note that this currently will not work properly in Flash due
to the limitations
* of the number type. Results are with only 32-bit precision.
(verify this?)
*
**/
class com.jbradley.math.LCG {
/* Period parameters */
static var M = Math.pow(2.8, 14); /* Period of LCG */
static var A = 2862933555777941757; /* 48-bit Mersenne Prime */
static var C = 3037000493; /* 16-bit prime? */
var time:Number = 0;
var seed:Number = 0;
function LCG(t)
{
if (arguments.length > 0)
{
init(t);
}
else
{
init();
}
}
public function init(t)
{
if (arguments.length > 0)
{
trace("reinitializing");
time = t;
seed = time&M;
}
else
{
// time seed not supplied by user, so we grab the
milliseconds
// on getTime() - similar to the way Math.getRandom()
works
time = new Date().getTime();
seed = time&M;
}
}
/* Returns a new random number every call */
public function random()
{
return randomReal48();
}
/*
This is the actual Linear Congruential Algorithm
LCGs have the form of: a = ( a * b + c ) % d;
where a = x[n] = (a x[n-1] + b) mod 2^48
The returned random number is calculated from the existing
seed, which changes each iteration.
Each time the algorithm runs, a new random number in the current
sequence is returned - the sequence is based on the initial
time seed.
*/
public function randomReal48()
{
seed = (seed*A + C) % M;
return seed / M;
}
public function getSeed():Number
{
trace(time);
return time;
}
}
On Nov 27, 2006, at 10:17 AM, Sascha wrote:
Thanks Ron and Danny!
I knew that the random numbers are not truly random and that the
seed cannot
be changed but the random number patterns I get now are pretty
hefty, I
think this wasn't like that in AS2 times.
I will try to fumble with the date object to get a better seed.
Sascha
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