Re: [Boost-users] Random: How to get a different seed?

Subject: Re: [Boost-users] Random: How to get a different seed?
From: Cedric Laczny (cedric.laczny_at_[hidden])
Date: 2011-01-24 16:27:17

On Monday, 24. January 2011 21:57:59 Lasse Kliemann wrote:
> * Message by -Cedric Laczny- from Mon 2011-01-24:
> > I use this approach:
> > 
> > #include <ctime>
> > #include <time.h>
> > #include <sys/time.h>
> > 
> >     struct timeval tv;
> >     gettimeofday(&tv, 0);
> >     long int seed;
> >     seed = (tv.tv_sec * 1000000) + tv.tv_usec;
> >     
> >     // Set the seed
> >    
> >    gen.seed( seed );
> > 
> > I am however not sure how exact it is (high precision timer?!) and if
> > there isn't probably a better way to get a fresh seed at every
> > execution. It might be that rapid subsequent executions will get the
> > same seed and thus will produce the same results.
> 
> I use /dev/urandom for this, like so (code fragments):
> 
>   FILE *dev_urandom;
>   uint32_t seed;
>   if((dev_urandom = fopen("/dev/urandom", "r")) == NULL) throw /* error */
>   if(fread(&seed, sizeof(seed), 1, dev_urandom) == 0) throw /* error */
>   if(fclose(dev_urandom) != 0) throw /* error */
>   boost::mt19937 gen(seed);
> 
> But maybe there are even better ways.

Interesting suggestion.

Thank you.

Best,

Cedric