Re: Using a different rng with std::random_shuffle

From:

Thomas <user@nl.invalid>

Newsgroups:

comp.lang.c++

Date:

Fri, 24 Dec 2010 14:03:45 +0100

Message-ID:

<if25nf$7s8$1@speranza.aioe.org>

On 24-12-2010 5:04, ?? Tiib wrote:

I believe that you need there a function accepting int parameter and
returning random int in range [0,parameter). It may be trivial like:

  int funcar( int x )
  {
      return rg.IRandom( 0, x );
  }

Just an example, i don't really know your TRandomMersenne's interface.

Thank you, ?? Tiib.

I got things working after studying the random_shuffle example at
http://www.cplusplus.com/reference/algorithm/random_shuffle/

I used Rick Wagner's Mersenne software:
http://www-personal.umich.edu/~wagnerr/MersenneTwister.html

Here is the essential code:

#include <iostream>
#include "MersenneTwister.h"
#include <vector>
#include <algorithm>

using namespace std;

MTRand mtrand1;

// random generator function:
ptrdiff_t myrandom (ptrdiff_t i)
{
     return mtrand1.randInt(i);
}

// pointer object to it:
ptrdiff_t (*p_myrandom)(ptrdiff_t) = myrandom;

int main()
{
     // A Mersenne Twister random number generator
     // can be declared with a simple

     //MTRand mtrand1;

     const int n = 10;
     vector<int> vint(n);
     for (int i = 0; i != n; ++i)
         vint[i] = i+1;
     random_shuffle (vint.begin(), vint.end(), p_myrandom);
     for (int i = 0; i != n; ++i)
         cout << vint[i] << ' ';

     return 0;
}

T.