RE: Random number generator

RE: Random number generator

[Erric Gilbert]

	I don't know of any number generators for C/C++ but there is a
built in $RANDOM function into BASH. You might be able to incorperate
that some how.

> -----Original Message-----
> From:	BMullenber [SMTP:BMullenber@aol.com]
> Sent:	Wednesday, January 07, 1998 3:05 AM
> To:	gnu-win32@cygnus.com
> Subject:	Random number generator
> 
> Anyone have the source code for a random number generator that
> actually works?
> 
> I am using C++
> 
> I am attempting to get random numbers between 0-100 for a game I wish
> to make
> that requires some sort of randomness with values.
> 
> If anyone has 1 that can do this, please send it or contact me
> 
> Thanks
> 
> Brandon
> BMullenber@aol.com
> -
> For help on using this list (especially unsubscribing), send a message
> to
> "gnu-win32-request@cygnus.com" with one line of text: "help".
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Re: Random number generator

[Tim Prince]

On Friday 03 May 2002 04:30, Paul Dilip K NPRI wrote:
> I am trying to use the random number generator for my fortran routine- but
> both RAN and SRAND does not work. Is there any other random number
> generating function which works with g77.
>
> Dilip K. Paul
>
> mailto:pauldk@npt.nuwc.navy.mil <mailto:pauldk@npt.nuwc.navy.mil>
Are you trying to start a flame war in an unusual place?  Why not simply look 
at the list of functions in 'info g77,' or in libg2c.a or the source, or, for 
more amusement, browse the comp.lang.fortran archive?  You don't say whether 
you're interested in portability, quality, speed, or any number of relevant 
factors.  Maybe a little research would help you decide.
-- 
Tim Prince

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RE: Random number generator

[Robinow, David]

http://gcc.gnu.org/ml/gcc-help/2002-02/msg00160.html

Please note that this is off-topic for this list.

-----Original Message-----
From: Paul Dilip K NPRI [mailto:PaulDK@Npt.NUWC.Navy.Mil]
Subject: Random number generator

I am trying to use the random number generator for my fortran routine- but
both RAN and SRAND does not work. Is there any other random number
generating function which works with g77.
Dilip K. Paul

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Random number generator

[Paul Dilip K NPRI]

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I am trying to use the random number generator for my fortran routine- but both RAN and SRAND does not work. Is there any other random number generating function which works with g77.

Dilip K. Paul

mailto:pauldk@npt.nuwc.navy.mil <mailto:pauldk@npt.nuwc.navy.mil> 



 

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RE: Random Number Generator

[Harold Hunt]

Beginning CS student?  Thought so :)

Let me teach you how to debug your program:
1) Change your line that calls rand () to:
	input1 = rand ();
2) Notice that random numbers are now generated.
3) Have your program print out the value of RAND_MAX:
	  printf ("RAND_MAX: %d\n", RAND_MAX);
4) Calculate the result, in integer math, when
	dividing any integer smaller than RAND_MAX by
	RAND_MAX.  (Hint: the answer is zero)
5) Realize that what you really wanted was something like:
	// Get random numbers from 0 and 9, inclusive
	input1 = rand () % 10;

	// Get random numbers from 1 and 10, inclusive
	input1 = 1 + rand () % 10;

That was your freebie, from now on, ask general programming questions to a
list that is more suited to answering such questions; or, better yet, read
some programming books :)

Harold


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Re: Random Number Generator

[DJ Delorie]

Sorry, fails on Linux also.  After fixing the bugs in your program
(missing stdio.h and stdlib.h) gcc complains about this:

r.c: In function `main':
r.c:11: warning: integer overflow in expression

rand() may return values close to the maximum allowable integer.
Multiplying them by 10 may cause overflow.  And, RAND_MAX+1 may not be
a valid integer (on Linux, RAND_MAX is INT_MAX, so RAND_MAX+1 is a
very negative number).

In short, your logic is flawed and the fact that it works "at
university" is pure coincidence.

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Re: Random Number Generator

[egor duda]

Hi!

Monday, 30 April, 2001 HRahman10@aol.com HRahman10@aol.com wrote:

Hac> Hi!, I'm writing a program using the random number genrator
Hac> rand() defined in <stdlib.h>.  I've written the following program
Hac> to test it:   

Hac> void main()
Hac> {
Hac>   int input1, i;
Hac>   srand(time(NULL));
Hac>   for (i=0; i<20 ; i++)
Hac>     {
Hac>       input1 = rand() * 10 / (RAND_MAX + 1);
Hac>       printf("random numbers %i\n",input1);
Hac>     }
Hac> } 


Hac> BUT, the results I get are all zeros.  Is there something wrong
Hac> with the gcc compiler provided by cygwin, because I've tested
Hac> this program at university, and it outputs random numbers
Hac> correctly.   

your program is wrong. RAND_MAX == INT_MAX == 0x7fffffff on cygwin.
so you've got integer overflow, RAND_MAX + 1 == -2147483648

Egor.            mailto:deo@logos-m.ru ICQ 5165414 FidoNet 2:5020/496.19



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Re: Random Number Generator

[Larry Hall (RFK Partners, Inc)]

At 01:37 PM 4/30/2001, you wrote:
>Hi!, I'm writing a program using the random number genrator rand() defined in <stdlib.h>.  I've written the following program to test it: 
>
>
>
>void main()
>{
>   int input1, i;
>
>   srand(time(NULL));
>   
>   for (i=0; i<20 ; i++)
>     {
>       input1 = rand() * 10 / (RAND_MAX + 1);
>       printf("random numbers %i\n",input1);
>
>     }
>} 
>
>
>BUT, the results I get are all zeros.  Is there something wrong with the gcc compiler provided by cygwin, because I've tested this program at university, and it outputs random numbers correctly.
>
>Please Help!
>
>Thank You!



Try the latest snapshot at www.cygwin.com.



Larry Hall                              lhall@rfk.com
RFK Partners, Inc.                      http://www.rfk.com
118 Washington Street                   (508) 893-9779 - RFK Office
Holliston, MA 01746                     (508) 893-9889 - FAX


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Re: Random Number Generator

[Noel L Yap]

Did you include stdlib.h?

Noel




HRahman10@aol.com on 2001.04.30 13:37:42

To:   cygwin@cygwin.com
cc:   (bcc: Noel L Yap)
Subject:  Random Number Generator




Hi!, I'm writing a program using the random number genrator rand() defined in
<stdlib.h>.  I've written the following program to test it:



void main()
{
  int input1, i;

  srand(time(NULL));

  for (i=0; i<20 ; i++)
    {
      input1 = rand() * 10 / (RAND_MAX + 1);
      printf("random numbers %i\n",input1);

    }
}


BUT, the results I get are all zeros.  Is there something wrong with the gcc
compiler provided by cygwin, because I've tested this program at university, and
it outputs random numbers correctly.

Please Help!

Thank You!

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Re: Random Number Generator

[Jonathon Merz]

A number of problems here...

   The reason only zeroes are being output is due to everything being 
interpreted as an integer and truncating to 0 when it is less than 1.  The 
best bet make the 10 that you multiply 10.0 or else cast it as float or 
double.If you desire integer results, you can then cast input1 as int when you 
need it as such.

   Another potential problem is (RAND_MAX +1).  This overflows (gcc gives a 
warning on compile), essentially giving you (RAND_MAX * -1) on any system 
where RAND_MAX is equal to MAX_INT, which as far as I know is most systems. 
If this is deliberate, for clearer coding, it would be better to write it as 
the latter, in addition to the fact, that if the code is ever compiled on a 
system where RAND_MAX is different than MAX_INT, it will not wrap, or else it 
may wrap differently.

In short, the following line:

    input1 = rand() * 10 / (RAND_MAX + 1);

should become:

    input1 = rand() * (float)10 / (RAND_MAX);

or:

    input1 = rand() * (float)10 / (RAND_MAX * -1);

if the negation of RAND_MAX was deliberate.


Hope this helps.

Jon

> Hi!, I'm writing a program using the random number genrator rand() defined in <stdlib.h>.  I've written the following program to test it: 
> 
> 
> void main()
> {
>   int input1, i;

> 
>   srand(time(NULL));
>   
>   for (i=0; i<20 ; i++)
>     {
>       input1 = rand() * 10 / (RAND_MAX + 1);
>       printf("random numbers %i\n",input1);
> 
>     }
> } 
> 
> 
> BUT, the results I get are all zeros.  Is there something wrong with the gcc compiler provided by cygwin, because I've tested this program at university, and it outputs random numbers correctly.




-- 


-------------------------------------
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  could they write like a monkey?


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Random Number Generator

[HRahman10]

Hi!, I'm writing a program using the random number genrator rand() defined in <stdlib.h>.  I've written the following program to test it: 



void main()
{
  int input1, i;

  srand(time(NULL));
  
  for (i=0; i<20 ; i++)
    {
      input1 = rand() * 10 / (RAND_MAX + 1);
      printf("random numbers %i\n",input1);

    }
} 


BUT, the results I get are all zeros.  Is there something wrong with the gcc compiler provided by cygwin, because I've tested this program at university, and it outputs random numbers correctly.

Please Help!

Thank You!

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Re: Random number generator

[Andrew Lipnitsky]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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BMullenber wrote:
Anyone have the source code for a random number generator
that actually works?

I am using C++

I am attempting to get random numbers between 0-100 for a game I wish
to make
that requires some sort of randomness with values.

If anyone has 1 that can do this, please send it or contact me
 
http://www.taygeta.com/random.htmlš
Random Number Generationš

Random number generator

[Patrick J. Fay]

Try:
PREINSTALLED /pfay/memory 262 > cat tst.c
#include <stdlib.h>
#include <math.h>
int rand100()
{
   double rmax=100.0/RAND_MAX;
   return((int)(rmax*(rand())));
}
int main()
{
   int i;

   for(i=0;i<10;i++)
   {
           printf("rand100=%d\n",rand100());
   }
   return 0;
}
PREINSTALLED /pfay/memory 263 > !gc
gcc tst.c -o tstc
PREINSTALLED /pfay/memory 264 > !./t
./tstc
rand100=51
rand100=17
rand100=30
rand100=53
rand100=94
rand100=17
rand100=70
rand100=22
rand100=49
rand100=12 

Patrick Fay, Ph.D., Intel Corp.            email:   pfay@co.intel.com
Los Alamos National Lab                    wk:         (505) 665-9141
CTI M.S. B296                              fax:        (505) 667-5921
Los Alamos NM 87545    ASCI-RED http://www.acl.lanl.gov/~pfay/teraflop

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Random number generator

[BMullenber]

Anyone have the source code for a random number generator that actually works?

I am using C++

I am attempting to get random numbers between 0-100 for a game I wish to make
that requires some sort of randomness with values.

If anyone has 1 that can do this, please send it or contact me

Thanks

Brandon
BMullenber@aol.com
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