rng_seed.hpp

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#ifndef RNG_SEED_HPP
#define RNG_SEED_HPP
 
#include "globals.hpp"
 
// RNG seed must be different for every MPI rank, and to be safe should be different for every call. The seeds should also be deterministic. So each call gets a different seed, by setting the seed equal to MPI rank and the stride equal to total number of ranks.
class RNGSeed{
    int seed;
    int stride;
 
    public:
 
    RNGSeed()
     : seed(0),
       stride(1){}
 
    void init(int new_seed, int new_stride){
        seed = new_seed;
        stride = new_stride;
    }
 
    int get_and_increment(){
        int out = seed;
 
        // Overflow might happen if there are many ranks and many time steps
        if(causes_addition_overflow(seed, stride)) exit_XGC("\nError: RNG Seed causes int overflow. Implement a reset.\n");
 
        seed += stride;
 
        return out;
    }
};
 
extern RNGSeed XGC_RNG_SEED;
 
#endif