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Re: [Help-gsl] Uniform random number generation

From: ozgur
Subject: Re: [Help-gsl] Uniform random number generation
Date: Thu, 27 Nov 2008 18:15:50 +0200

On Thu, Nov 27, 2008 at 3:41 PM, Maxime Boissonneault <
address@hidden> wrote:

> I would say to initialize the seed only once when the program starts (ie
> keep the random generator in a static variable). Also, you could use a more
> precise time function which returns the number of ticks (CPU cycles) and not
> the number of seconds or milliseconds.
> Maxime Boissonneault

I did something like this ( copying from the previous posts  to the list;
sorry for duplication, i had not done an elaborate search that time)  using
/dev/random . It works fine for now. But i did not understand a thing in
your reply Maxime . If i keep random generator in a static variable, how can
it return different serie each time when i call it? BTW thanks for the quick

vector<double> rn_uniform(int n)
    vector<double> rn_array;
    // Define GSL RNG parameters.
    const gsl_rng_type * T;
    gsl_rng *r;

    T = gsl_rng_taus2; // RNG type
    r = gsl_rng_alloc(T);// Allocate memory

    unsigned int stb_seed = rand(); // System time based random seed
    unsigned int seed;

    FILE *dev_random;
    dev_random = fopen("/dev/random","r");
    if (dev_random == NULL)
        fprintf(stderr,"Can not open /dev/random - seeding failed\n");
        seed = stb_seed;
        fread(&seed , sizeof(seed), 1, dev_random);

    gsl_rng_set(r, seed); // Set the seed for GSL RNG

    int i;
    for(i=0; i< n; i++)
            double u = gsl_rng_uniform(r);

    gsl_rng_free(r); // Free memory

    return rn_array;


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