NAG Library Function Document
nag_rand_logarithmic (g05tfc) generates a vector of pseudorandom integers from the discrete logarithmic distribution with parameter .
||nag_rand_logarithmic (Nag_ModeRNG mode,
nag_rand_logarithmic (g05tfc) generates
from a discrete logarithmic distribution, where the probability of
The variates can be generated with or without using a search table and index. If a search table is used then it is stored with the index in a reference vector and subsequent calls to
nag_rand_logarithmic (g05tfc) with the same parameter value can then use this reference vector to generate further variates.
One of the initialization functions nag_rand_init_repeatable (g05kfc)
(for a repeatable sequence if computed sequentially) or nag_rand_init_nonrepeatable (g05kgc)
(for a non-repeatable sequence) must be called prior to the first call to nag_rand_logarithmic (g05tfc).
Knuth D E (1981) The Art of Computer Programming (Volume 2) (2nd Edition) Addison–Wesley
mode – Nag_ModeRNGInput
: a code for selecting the operation to be performed by the function.
- Set up reference vector only.
- Generate variates using reference vector set up in a prior call to nag_rand_logarithmic (g05tfc).
- Set up reference vector and generate variates.
- Generate variates without using the reference vector.
, , or .
n – IntegerInput
On entry: , the number of pseudorandom numbers to be generated.
a – doubleInput
On entry: , the parameter of the logarithmic distribution.
r[lr] – doubleCommunication Array
, the reference vector from the previous call to nag_rand_logarithmic (g05tfc).
is not referenced and may be NULL
On exit: , the reference vector.
lr – IntegerInput
: the dimension of the array r
- if , ;
- otherwise .
- if or , lr must not be too small, but the lower limit is too complicated to specify;
- if , lr must remain unchanged from the previous call to nag_rand_logarithmic (g05tfc).
state – IntegerCommunication Array
, of this array is dictated by the requirements of associated functions that must have been previously called. This array MUST be the same array passed as argument state
in the previous call to nag_rand_init_repeatable (g05kfc)
or nag_rand_init_nonrepeatable (g05kgc)
On entry: contains information on the selected base generator and its current state.
On exit: contains updated information on the state of the generator.
x[n] – IntegerOutput
On exit: the pseudorandom numbers from the specified logarithmic distribution.
fail – NagError *Input/Output
The NAG error argument (see Section 3.6
in the Essential Introduction).
6 Error Indicators and Warnings
On entry, argument had an illegal value.
On entry, lr
is too small when
, minimum length required
On entry, .
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
On entry, state
vector has been corrupted or not initialized.
The value of a
is not the same as when r
was set up in a previous call.
Previous value of
On entry, .
On entry, some of the elements of the array r
have been corrupted or have not been initialized.
8 Parallelism and Performance
This example prints
pseudorandom integers from a logarithmic distribution with parameter
, generated by a single call to nag_rand_logarithmic (g05tfc), after initialization by nag_rand_init_repeatable (g05kfc)
10.1 Program Text
Program Text (g05tfce.c)
10.2 Program Data
10.3 Program Results
Program Results (g05tfce.r)