mersenne.h

// Copyright 2009-2020 NTESS. Under the terms
// of Contract DE-NA0003525 with NTESS, the U.S.
// Government retains certain rights in this software.
//
// Copyright (c) 2009-2020, NTESS
// All rights reserved.
//
// This file is part of the SST software package. For license
// information, see the LICENSE file in the top level directory of the
// distribution.

#ifndef SST_CORE_RNG_MERSENNE_H
#define SST_CORE_RNG_MERSENNE_H

#include <stdint.h>
#include <sys/time.h>

#include "sstrng.h"

#define MERSENNE_UINT32_MAX 4294967295U
#define MERSENNE_UINT64_MAX 18446744073709551615ULL
#define MERSENNE_INT32_MAX  2147483647L
#define MERSENNE_INT64_MAX  9223372036854775807LL

namespace SST {
namespace RNG {
/**
    \class MersenneRNG mersenne.h "sst/core/rng/mersenne.h"

    Implements a Mersenne-based RNG for use in the SST core or components. The Mersenne
    RNG provides a better "randomness" to the distribution of outputs but is computationally
    more expensive than the Marsaglia RNG.
*/
class MersenneRNG : public SSTRandom {

public:
    /**
       Create a new Mersenne RNG with a specified seed
       @param[in] seed The seed for this RNG
    */
    MersenneRNG(unsigned int seed);

    /**
       Creates a new Mersenne using a random seed which is obtained from the system
       clock. Note this will give different results on different platforms and between
       runs.
    */
    MersenneRNG();

    /**
       Generates the next random number as a double value between 0 and 1.
    */
    double   nextUniform() override;

    /**
       Generates the next random number as an unsigned 32-bit integer
    */
    uint32_t generateNextUInt32() override;

    /**
       Generates the next random number as an unsigned 64-bit integer
    */
    uint64_t generateNextUInt64() override;

    /**
       Generates the next random number as a signed 64-bit integer
    */
    int64_t  generateNextInt64() override;

    /**
       Generates the next random number as a signed 32-bit integer
    */
    int32_t  generateNextInt32() override;

    /**
       Seed the XOR RNG
    */
    void seed(uint64_t newSeed);

    /**
       Destructor for Mersenne
    */
    ~MersenneRNG();

    private:
    /**
       Generates the next batch of random numbers
    */
    void  generateNextBatch();

    /**
       Stores the next set of random numbers
    */
    uint32_t* numbers;

    /**
       Tells us what index of the random number list the next returnable number should come from
    */
    int index;

};

} //namespace RNG
} //namespace SST

#endif //SST_CORE_RNG_MERSENNE_H