Chapter 4: Generating Random Numbers

4.1: Random

Objects of the class Random generate random numbers. The generator itself is the mercenne twister defined in C++'s STL (as the std::mt19937 type). Its public members are

        void reset(size_t seed);

        double uniform();
        double normal();
        double logNormal(double mean, double stdDev);
        double exponential(double mean);

The members uniform, normal, logNormal and exponential generate random numbers conforming their distribution type.

To reset the mt19937 mercenne twister the member reset is called,, providing it with a seed.

There are three ways of resetting the random number generator:

by default the computer's time in seconds since the epoch is used as seed value, corresponding to the generator: random configuration file specification (corresponding to the program's enumeration value SeedType::RANDOM_SEED);
it may be reset using a fixed value (specified as generator: fixed), using the value specified at seed: in the configuration file (corresponding to the program's enumeration value SeedType::FIXED_SEED);
the initial seed value may be incremented at the Loop's next iteration (specified as generator: increasing)

The random number generator is reset in Loop::initialize (or by Loop::checkSeed called from Loop::initialize) (cf. section 2.5).