rocrand_threefry2x64_20.h

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/*
Copyright 2010-2011, D. E. Shaw Research.
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* Neither the name of D. E. Shaw Research nor the names of its
  contributors may be used to endorse or promote products derived from
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#ifndef ROCRAND_THREEFRY2X64_20_H_
#define ROCRAND_THREEFRY2X64_20_H_

#include "rocrand/rocrand_threefry2_impl.h"

namespace rocrand_device
{

class threefry2x64_20_engine : public threefry_engine2_base<ulonglong2, unsigned long long, 20>
{
public:
    ROCRAND_DEPRECATED("Alias \"threefry2x64_20_state\" is deprecated. Use \"state_type\" instead.")
    typedef threefry_engine2_base<ulonglong2, unsigned long long, 20>::threefry_state_2
        threefry2x64_20_state;

    /// Initializes the internal state of the PRNG using
    /// seed value \p seed, goes to \p subsequence -th subsequence,
    /// and skips \p offset random numbers.
    ///
    /// A subsequence consists of 2 ^ 65 random numbers.
    __forceinline__ __device__ __host__ threefry2x64_20_engine(const unsigned long long seed = 0,
                                                               const unsigned long long subsequence
                                                               = 0,
                                                               const unsigned long long offset = 0)
    {
        this->seed(seed, subsequence, offset);
    }

    /// Reinitializes the internal state of the PRNG using new
    /// seed value \p seed_value, skips \p subsequence subsequences
    /// and \p offset random numbers.
    ///
    /// A subsequence consists of 2 ^ 65 random numbers.
    __forceinline__ __device__ __host__ void seed(const unsigned long long seed        = 0,
                                                  const unsigned long long subsequence = 0,
                                                  const unsigned long long offset      = 0)
    {
        m_state.counter  = {0ULL, 0ULL};
        m_state.key      = {seed, seed >> 32};
        m_state.result   = {0ULL, 0ULL};
        m_state.substate = 0;

        this->discard_subsequence_impl(subsequence);
        this->discard(offset);
        m_state.result = this->threefry_rounds(m_state.counter, m_state.key);
    }

}; // threefry2x64_20_engine class

} // end namespace rocrand_device

typedef rocrand_device::threefry2x64_20_engine rocrand_state_threefry2x64_20;

/**
 * \brief Initializes Threefry state.
 *
 * Initializes the Threefry generator \p state with the given
 * \p seed, \p subsequence, and \p offset.
 *
 * \param seed Value to use as a seed
 * \param subsequence Subsequence to start at
 * \param offset Absolute offset into subsequence
 * \param state Pointer to state to initialize
 */
__forceinline__ __device__ __host__
void rocrand_init(const unsigned long long       seed,
                  const unsigned long long       subsequence,
                  const unsigned long long       offset,
                  rocrand_state_threefry2x64_20* state)
{
    *state = rocrand_state_threefry2x64_20(seed, subsequence, offset);
}

/**
 * \brief Returns uniformly distributed random <tt>unsigned long long</tt> value
 * from [0; 2^64 - 1] range.
 *
 * Generates and returns uniformly distributed random <tt>unsigned long long</tt>
 * value from [0; 2^64 - 1] range using Threefry generator in \p state.
 * State is incremented by one position.
 *
 * Threefry2x64 has a period of 2 ^ 128 numbers.
 *
 * \param state Pointer to a state to use
 *
 * \return Pseudorandom value (64-bit) as an <tt>unsigned long long</tt>
 */
__forceinline__ __device__ __host__
unsigned long long rocrand(rocrand_state_threefry2x64_20* state)
{
    return state->next();
}

/**
 * \brief Returns two uniformly distributed random <tt>unsigned long long</tt> values
 * from [0; 2^64 - 1] range.
 *
 * Generates and returns two uniformly distributed random <tt>unsigned long long</tt>
 * values from [0; 2^64 - 1] range using Threefry generator in \p state.
 * State is incremented by two positions.
 *
 * \param state Pointer to a state to use
 *
 * \return Two pseudorandom values (64-bit) as an <tt>ulonglong2</tt>
 */
__forceinline__ __device__ __host__
ulonglong2 rocrand2(rocrand_state_threefry2x64_20* state)
{
    return state->next2();
}

#endif // ROCRAND_THREEFRY2X64_20_H_