int i4_normal ( float a, float b, int *seed )
/******************************************************************************/
/*
Purpose:
I4_NORMAL returns a scaled pseudonormal I4.
Discussion:
The normal probability distribution function (PDF) is sampled,
with mean A and standard deviation B.
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
02 July 2006
Author:
John Burkardt
Parameters:
Input, float A, the mean of the PDF.
Input, float B, the standard deviation of the PDF.
Input/output, int *SEED, a seed for the random number generator.
Output, int I4_NORMAL, a sample of the normal PDF.
*/
{
int value;
value = r4_nint ( a + b * r4_normal_01 ( seed ) );
return value;
}
int i4_uniform ( int a, int b, int *seed )
/******************************************************************************/
/*
Purpose:
I4_UNIFORM returns a scaled pseudorandom I4.
Discussion:
The pseudorandom number should be uniformly distributed
between A and B.
Licensing:
This code is distributed under the GNU LGPL license.
Modified:
12 November 2006
Author:
John Burkardt
Reference:
Paul Bratley, Bennett Fox, Linus Schrage,
A Guide to Simulation,
Springer Verlag, pages 201-202, 1983.
Pierre L'Ecuyer,
Random Number Generation,
in Handbook of Simulation,
edited by Jerry Banks,
Wiley Interscience, page 95, 1998.
Bennett Fox,
Algorithm 647:
Implementation and Relative Efficiency of Quasirandom
Sequence Generators,
ACM Transactions on Mathematical Software,
Volume 12, Number 4, pages 362-376, 1986.
Peter Lewis, Allen Goodman, James Miller
A Pseudo-Random Number Generator for the System/360,
IBM Systems Journal,
Volume 8, pages 136-143, 1969.
Parameters:
Input, int A, B, the limits of the interval.
Input/output, int *SEED, the "seed" value, which should NOT be 0.
On output, SEED has been updated.
Output, int I4_UNIFORM, a number between A and B.
*/
{
int k;
float r;
int value;
if ( *seed == 0 )
{
fprintf ( stderr, "\n" );
fprintf ( stderr, "I4_UNIFORM - Fatal error!\n" );
fprintf ( stderr, " Input value of SEED = 0.\n" );
exit ( 1 );
}
k = *seed / 127773;
*seed = 16807 * ( *seed - k * 127773 ) - k * 2836;
if ( *seed < 0 )
{
*seed = *seed + 2147483647;
}
r = ( float ) ( *seed ) * 4.656612875E-10;
/*
Scale R to lie between A-0.5 and B+0.5.
*/
r = ( 1.0 - r ) * ( ( float ) ( i4_min ( a, b ) ) - 0.5 )
+ r * ( ( float ) ( i4_max ( a, b ) ) + 0.5 );
/*
Use rounding to convert R to an integer between A and B.
*/
value = r4_nint ( r );
value = i4_max ( value, i4_min ( a, b ) );
value = i4_min ( value, i4_max ( a, b ) );
return value;
}
