Generates a pseudorandom permutation.

Synopsis

#include <imsls.h>

int *imsls_random_permutation (int k, ..., 0)

Required Arguments

int k   (Input)
Number of integers to be permuted.

Return Value

An array of length k containing the random permutation of the integers from
1 to k. To release this space, use free.

Synopsis with Optional Arguments

#include <imsls.h>

int *imsls_random_permutation (int k,
 IMSLS_RETURN_USER, int ir[],
 0)

Optional Arguments

IMSLS_RETURN_USER, int ir[]  (Output)
User-supplied array of length k containing the random permutation of the integers from 1 to k.

Description

Routine imsls_random_permutation generates a pseudorandom permutation of the integers from 1 to k. It begins by filling a vector of length k with the consecutive integers 1 to k. Then, with M initially equal to k, a random index J between 1 and M (inclusive) is generated. The element of the vector with the index M and the element with index J swap places in the vector. M is then decremented by 1 and the process repeated until M = 1.

Example

In this example, imsls_random_permutation is called to produce a pseudorandom permutation of the integers from 1 to 10.

#include <stdio.h>

#include <imsls.h>

 

int main()

{

  int *ir, k = 10;

 

  imsls_random_seed_set(123457);

 

  ir = imsls_random_permutation(k, 0);

  printf("Random permutation of the integers from 1 to 10\n");      

  imsls_i_write_matrix("", 1, k, ir,

                     IMSLS_NO_COL_LABELS, 0);

 }

 

 

 

Output

Random permutation of the integers from 1 to 10

 

  5    9    2    8    1    6    4    7    3   10

 

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