NAG CL Interface
g05kfc (init_​repeat)

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1 Purpose

g05kfc initializes the selected base generator, as used by the group of pseudorandom number functions (see g05khcg05kjc, g05ncc, g05ndc, g05pdcg05pjc, g05pxcg05pzc, g05rcc, g05rdc, g05ryc, g05rzc and g05sacg05tlc), so as to generate a repeatable sequence of variates and the quasi-random scrambled sequence initialization function, g05ync.

2 Specification

#include <nag.h>
void  g05kfc (Nag_BaseRNG genid, Integer subid, const Integer seed[], Integer lseed, Integer state[], Integer *lstate, NagError *fail)
The function may be called by the names: g05kfc, nag_rand_init_repeat or nag_rand_init_repeatable.

3 Description

g05kfc selects a base generator through the input value of the arguments genid and subid, and then initializes it based on the values given in the array seed.
A given base generator will yield different sequences of random numbers if initialized with different values of seed. Alternatively, the same sequence of random numbers will be generated if the same value of seed is used. It should be noted that there is no guarantee of statistical properties between sequences, only within sequences.
A definition of some of the terms used in this description, along with details of the various base generators can be found in the G05 Chapter Introduction.

4 References

L'Ecuyer P and Simard R (2002) TestU01: a software library in ANSI C for empirical testing of random number generators Departement d'Informatique et de Recherche Operationnelle, Universite de Montreal
Maclaren N M (1989) The generation of multiple independent sequences of pseudorandom numbers Appl. Statist. 38 351–359
Matsumoto M and Nishimura T (1998) Mersenne twister: a 623-dimensionally equidistributed uniform pseudorandom number generator ACM Transactions on Modelling and Computer Simulations
Wichmann B A and Hill I D (2006) Generating good pseudo-random numbers Computational Statistics and Data Analysis 51 1614–1622
Wikramaratna R S (1989) ACORN - a new method for generating sequences of uniformly distributed pseudo-random numbers Journal of Computational Physics 83 16–31

5 Arguments

1: genid Nag_BaseRNG Input
On entry: must contain the type of base generator to use.
NAG basic generator.
Wichmann Hill I generator.
Mersenne Twister.
Wichmann Hill II generator.
ACORN generator.
L'Ecuyer MRG32k3a generator.
See the G05 Chapter Introduction for details of each of the base generators.
Constraint: genid=Nag_Basic, Nag_WichmannHill_I, Nag_MersenneTwister, Nag_WichmannHill_II, Nag_ACORN or Nag_MRG32k3a.
2: subid Integer Input
On entry: if genid=Nag_WichmannHill_I, subid indicates which of the 273 sub-generators to use. In this case, the ((|subid|+272) mod 273) + 1 sub-generator is used.
If genid=Nag_ACORN, subid indicates the values of k and p to use, where k is the order of the generator, and p controls the size of the modulus, M, with M = 2 (p×30) . If subid<1, the default values of k=10 and p=2 are used, otherwise values for k and p are calculated from the formula, subid=k+1000(p-1).
If genid=Nag_MRG32k3a and subid mod 2=0 the range of the generator is set to (0,1], otherwise the range is set to (0,1); in this case the sequence is identical to the implementation of MRG32k3a in TestU01 (see L'Ecuyer and Simard (2002)) for identical seeds.
For all other values of genid, subid is not referenced.
3: seed[lseed] const Integer Input
On entry: the initial (seed) values for the selected base generator. The number of initial values required varies with each of the base generators.
If genid=Nag_Basic, one seed is required.
If genid=Nag_WichmannHill_I, four seeds are required.
If genid=Nag_MersenneTwister, 624 seeds are required.
If genid=Nag_WichmannHill_II, four seeds are required.
If genid=Nag_ACORN, (k+1)p seeds are required, where k and p are defined by subid. For the ACORN generator it is recommended that an odd value is used for seed[0].
If genid=Nag_MRG32k3a, six seeds are required.
If insufficient seeds are provided then the first lseed-1 values supplied in seed are used and the remaining values are randomly generated using the NAG basic generator. In such cases the NAG basic generator is initialized using the value supplied in seed[lseed-1].
Constraint: seed[i-1]1, for i=1,2,,lseed.
4: lseed Integer Input
On entry: the size of the seed array.
Constraint: lseed1.
5: state[lstate] Integer Communication Array
On exit: contains information on the selected base generator and its current state. If lstate<1 then state may be NULL.
6: lstate Integer * Input/Output
On entry: the dimension of the state array, or a value <1. If the Mersenne Twister (genid=Nag_MersenneTwister) is being used and the skip ahead function g05kjc or g05kkc will be called subsequently, then you must ensure that lstate1260.
On exit: if lstate<1 on entry, then the required length of the state array for the chosen base generator, otherwise lstate is unchanged. When genid=Nag_MersenneTwister (Mersenne Twister) a value of 1260 is returned, allowing for the skip ahead function to be subsequently called. In all other cases the minimum length, as documented in the constraints below, is returned.
  • if genid=Nag_Basic, lstate17;
  • if genid=Nag_WichmannHill_I, lstate21;
  • if genid=Nag_MersenneTwister, lstate633;
  • if genid=Nag_WichmannHill_II, lstate29;
  • if genid=Nag_ACORN, lstatemax((k+1)×p+9,14)+3, where k and p are defined by subid;
  • if genid=Nag_MRG32k3a, lstate61;
  • otherwise lstate<1.
7: fail NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
On entry, argument value had an illegal value.
On entry, lseed=value.
Constraint: lseed1.
On entry, lstate=value.
Constraint: lstate0 or lstatevalue.
On entry, invalid seed.
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.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
g05kfc is not threaded in any implementation.

9 Further Comments


10 Example

This example prints the first five pseudorandom real numbers from a uniform distribution between 0 and 1, generated by g05sac after initialization by g05kfc.

10.1 Program Text

Program Text (g05kfce.c)

10.2 Program Data


10.3 Program Results

Program Results (g05kfce.r)