AMDG On 1/24/2011 11:29 AM, Anton Skvorts wrote:
Testing boost::random with the following code
boost::mt19937 gener(1); boost::normal_distribution<> normal(0,1); boost::variate_generator<boost::mt19937&,boost::normal_distribution<> > rng(gener, normal); cout<< rng()<< endl; cout<< rng()<< endl; cout<< rng()<< endl; gener.seed(2); cout<< rng()<< endl; cout<< rng()<< endl; cout<< rng()<< endl;
I'm getting unexpected values after gener.seed(2) -2.971829031 1.706951063 -0.430498971
-2.282022417 x -0.5887503675 0.2504171986
The value -2.282022417 is the forth number in the sequence originated by gener(1) and not the first number in the sequence originated by gener.seed(2) as one would expect (this number is actually -0.5887503675). If I reseed next with gener.seed(3)it works fine, but if after that I reseed again with gener.seed(1) I'll get the same problem, and so on and off...
How can I reseed the random number generator to overcome this problem?
This is because normal_distribution uses Box-Muller, which generates pairs of normal variates. You need to call rng.distribution().reset() to clear the cached result. In Christ, Steven Watanabe