nag_rngs_discrete_uniform (g05mac) (PDF version)
g05 Chapter Contents
g05 Chapter Introduction
NAG C Library Manual

NAG Library Function Document

nag_rngs_discrete_uniform (g05mac)

+ Contents

    1  Purpose
    7  Accuracy

1  Purpose

nag_rngs_discrete_uniform (g05mac) generates a vector of pseudorandom integers uniformly distributed over the interval a,b.

2  Specification

#include <nag.h>
#include <nagg05.h>
void  nag_rngs_discrete_uniform (Integer a, Integer b, Integer n, Integer x[], Integer igen, Integer iseed[], NagError *fail)

3  Description

nag_rngs_discrete_uniform (g05mac) generates the next n values yi from a uniform 0,1 generator (see nag_rngs_basic (g05kac) for details) and applies the transformation
xi=a+b-a+1yi,
where z is the integer part of the real value z. The function ensures that the values xi lie in the closed interval a,b.
One of the initialization functions nag_rngs_init_repeatable (g05kbc) (for a repeatable sequence if computed sequentially) or nag_rngs_init_nonrepeatable (g05kcc) (for a non-repeatable sequence) must be called prior to the first call to nag_rngs_discrete_uniform (g05mac).

4  References

Knuth D E (1981) The Art of Computer Programming (Volume 2) (2nd Edition) Addison–Wesley

5  Arguments

1:     aIntegerInput
2:     bIntegerInput
On entry: the end points a and b of the uniform distribution.
Constraint: ab.
3:     nIntegerInput
On entry: n, the number of pseudorandom numbers to be generated.
Constraint: n0.
4:     x[n]IntegerOutput
On exit: the n pseudorandom numbers from the specified uniform distribution.
5:     igenIntegerInput
On entry: must contain the identification number for the generator to be used to return a pseudorandom number and should remain unchanged following initialization by a prior call to nag_rngs_init_repeatable (g05kbc) or nag_rngs_init_nonrepeatable (g05kcc).
6:     iseed[4]IntegerCommunication Array
On entry: contains values which define the current state of the selected generator.
On exit: contains updated values defining the new state of the selected generator.
7:     failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, n=value.
Constraint: n0.
NE_INT_2
On entry, a=value and b=value.
Constraint: ba.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

This example prints five pseudorandom integers from a discrete uniform distribution between -5 and 5, generated by a single call to nag_rngs_discrete_uniform (g05mac), after initialization by nag_rngs_init_repeatable (g05kbc).

9.1  Program Text

Program Text (g05mace.c)

9.2  Program Data

None.

9.3  Program Results

Program Results (g05mace.r)


nag_rngs_discrete_uniform (g05mac) (PDF version)
g05 Chapter Contents
g05 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012