|
|
| |
|
code:
Can't Copy and Paste this?
Click here for a copy-and-paste friendly version of this code!
Terms of Agreement:
By using this code, you agree to the following terms...
1) You may use
this code in your own programs (and may compile it into a program and distribute it in compiled format for languages that allow it) freely and with no charge.
2) You MAY NOT redistribute this code (for example to a web site) without written permission from the original author. Failure to do so is a violation of copyright laws.
3) You may link to this code from another website, but ONLY if it is not wrapped in a frame.
4) You will abide by any additional copyright restrictions which the author may have placed in the code or code's description. |
//**************************************
//
// Name: A better Random Number Generato
// r
// Description:This is a better random n
// umber generator than comes standard. It'
// s from a very good book on algoritms. Yo
// u should read it
// By: Andy Williams
//
//This code is copyrighted and has// limited warranties.Please see http://
// www.Planet-Source-Code.com/xq/ASP/txtCod
// eId.239/lngWId.3/qx/vb/scripts/ShowCode.
// htm//for details.//**************************************
//
#include <iostream.h>
#include <time.h>
void init_mm( );
int number_range( int from, int to );
int number_mm( void );
static int rgiState[2+55]; // leave this alone
void main()
{
init_mm(); //seed the number generator
int random = number_range( 10, 100 );
cout << random << endl;
}
int number_mm( void )
{
int *piState;
int iState1;
int iState2;
int iRand;
piState = &rgiState;[2];
iState1 = piState[-2];
iState2 = piState[-1];
iRand = ( piState[iState1] + piState[iState2] )
& ( ( 1 << 30 ) - 1 );
piState[iState1] = iRand;
if ( ++iState1 == 55 )
iState1 = 0;
if ( ++iState2 == 55 )
iState2 = 0;
piState[-2] = iState1;
piState[-1] = iState2;
return iRand >> 6;
}
/*
* Generate a random number.
*/
int number_range( int from, int to )
{
int power;
int number;
if ( ( to = to - from + 1 ) <= 1 )
return from;
for ( power = 2; power < to; power <<= 1 )
;
while ( ( number = number_mm( ) & ( power - 1 ) ) >= to )
;
return from + number;
}
/*
* this is the Mitchell-Moore algorithm from Knuth Volume II.
*/
void init_mm( )
{
int *piState;
int iState;
piState = &rgiState;[2];
piState[-2] = 55 - 55;
piState[-1] = 55 - 24;
piState[0] = ( (int) time( NULL ) ) & ( ( 1 << 30 ) - 1 );
piState[1] = 1;
for ( iState = 2; iState < 55; iState++ )
{
piState[iState] = ( piState[iState-1] + piState[iState-2] )
& ( ( 1 << 30 ) - 1 );
}
return;
}
| |
Other 3 submission(s) by this author
|
|
| |
| Report Bad Submission |
|
| |
| Your Vote! |
|
See Voting Log |
| |
| Other User Comments |
2/14/2000 9:49:18 AM:tony
briliant
|
9/2/2000 4:12:37 AM:Skuggi
Hmmm... this thing wont be compiled.
the compiler gives me these two error
messages:
Error E2268 random1.cpp
33: Call to undefined function 'int_mm'
in function main()
and
Error
E2451 random1.cpp 45: Undefined symbol
'rgiState' in function
number_mm()
i'm using borland c++
5.5 compiler.
What is wrong??
|
9/2/2000 9:54:34 AM:Lolindrath
Look closely at your errors, the
function name is init_mm, not int_mm.
init_mm initializes the random number
generator. Double check that the
rgiState[2+55]; looks like it does in
my submission. It kind of looks like it
got commented out or something.
|
10/30/2000 12:14:44 PM:Leo Tokarski
Excellent! Finally, a random
number
generator where the range
variables
aren't constants! The
single typo was
easily edited...just
replace the "void
int_mm();" line in
main() with "void
init_mm();".
|
11/24/2000 2:50:28 PM:Jonathan Barber
I am compiling this code on a non
Borland compiler on a vax or unix
terminal. It is giving me an error
with time(NULL), which is in init_mm().
If you have an suggestions, let me
know.
|
4/13/2001 1:00:01 PM:ejoeli@hotmail.com
great - may need to re-order the
functions here but otherwise works just
fine. may need to add #include
|
4/13/2001 1:01:25 PM:ejoeli@homail
may need to add #include
|
4/13/2001 1:02:37 PM:#include
ejoeli@hotmail.com
|
4/13/2001 1:03:20 PM:ejoeli@hotmail
time.h
|
5/23/2001 10:10:36 PM:Andy Williams
Ok guys, I fixed all the problems with
that, I'm sorry I neglected it for so
long. It should run rather well
now.
Andy
|
6/25/2001 4:38:52 AM:Vitaly Belman
Something is wrong with this code:
for(int i=0; i<10;
i++)
{
init_mm(); //seed the number
generator
int random = number_range(
10, 100 );
cout << random <<
endl;
}
The following code
generates 10 times the same number.
What's wrong?
|
8/16/2001 11:01:02 PM:Greg Toombs
Instead of using time(NULL) to
initialize your random data, use
QueryPerformanceCounter. It's much,
much, much, MUCH more effective.
|
9/1/2001 12:58:45 AM:Dustin Davis
Yeah if i put this a loop, i get the
same number no matter how many times i
run it, i got the same number, i am
calling all three lines fo coed in the
loop, should i not do that?
|
9/1/2001 1:00:31 AM:Dustin Davis
Never mind, i got it working, do not
put the init_mm in the loop, or it will
get the same number over and over, call
it once and make sure to set int random
before you set its random value.
int
random;
random = blah blah...
|
9/1/2001 11:19:43 AM:Andrew Williams
You got it, if you keep re-seeding the
random number then you'll keep getting
the same number. I'm not sure why this
happens though.
|
1/17/2002 7:34:09 PM:Curtis Miller
Like it alot get a different number
almost every time. It seems to work
better than rando.h. Think it would be
cool if you made it a class. I did that
and i makes it easier to just call it.
|
2/2/2002 12:43:31 PM:wynx
What is the function of the rgiState ?
You wrote there leave it alone.. but
what's the use of it ?
|
2/2/2002 11:53:44 PM:wynx
I am just a begineer, so I am not clear
about this. Why don't you use
srand(time(NULL));
randomNum=rand();
to generate random number ? isn't it
easier than using all the complex
function? If you don't mind, can you
explain what's the logic/ idea you used
to generate the random number?
|
5/28/2002 4:20:04 AM:dathui
I just find one bad thing with this
code, it always generate the same
number the whole second, if you try
looping it, it will show the same
number until a new second begin.
|
6/17/2002 10:36:31 PM:Joseph
Nice code.
Would you please let us
know which book was that? "very good
book on algoritms"
Thanks
|
10/8/2002 10:57:18 AM:
This is great, I had to add a line(or
three) to see the results of the
generator before it closed.
|
|
| Add Your Feedback! |
Note:Not only will your feedback be posted, but an email will be sent to the code's author in your name.
NOTICE: The author of this code has been kind enough to share it with you. If you have a criticism, please state it politely or it will be deleted.
For feedback not related to this particular code, please click here.
|
|
