random_well512a_simd/RandomWELL512a_SSE2.h

// Copyright (c) 2013, Peter Pettersson
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// The views and conclusions contained in the software and documentation are those
// of the authors and should not be interpreted as representing official policies,
// either expressed or implied, of the FreeBSD Project.

#ifndef RANDOM_WELL512A_SSE2_H
#define RANDOM_WELL512A_SSE2_H

#include <emmintrin.h>	// SSE2 instrinsics.
#include <stdlib.h>		// Needed for rand().

class RandomWELL512a_SSE2
{
public:
    RandomWELL512a_SSE2(int seed);
    RandomWELL512a_SSE2(unsigned *seed);

    unsigned GetUnsigned();
    double GetDouble();

    void GetUnsigned4(unsigned *result4);
    void GetDouble4(double *result4);

private:
    __m128i     state[16];
    unsigned    result[4];
    unsigned    index;
    unsigned    result_index;
};


inline RandomWELL512a_SSE2::RandomWELL512a_SSE2(int seed)
    : index(0)
    , result_index(4)
{
    srand(seed);
    for (int i = 0; i < 16; ++i)
        state[i] = _mm_set_epi32(rand(), rand(), rand(), rand());
}

inline RandomWELL512a_SSE2::RandomWELL512a_SSE2(unsigned *seed)
    : index(0)
    , result_index(4)
{
    for (int i = 0; i < 16; ++i)
        state[i] = _mm_set_epi32(seed[i + 48], seed[i + 32], seed[i + 16], seed[i]);
}

inline unsigned RandomWELL512a_SSE2::GetUnsigned()
{
    if (result_index >= 4)
    {
        GetUnsigned4(result);
        result_index = 0;
    }
    return result[result_index++];
}

inline double RandomWELL512a_SSE2::GetDouble()
{
    const double kToFloat = 2.32830643653869628906e-10;
    return GetUnsigned() * kToFloat;
}

inline void RandomWELL512a_SSE2::GetUnsigned4(unsigned *result4)
{
    unsigned index_15		= (index + 15) & 15;
    __m128i state_index		= state[index];
    __m128i state_index_9	= state[(index +  9) & 15];
    __m128i state_index_13	= state[(index + 13) & 15];
    __m128i state_index_15	= state[index_15];
    const __m128i kMix		= _mm_set1_epi32(0xda442d24);

    __m128i left    = _mm_xor_si128(state_index, _mm_slli_epi32(state_index, 16));
    __m128i right   = _mm_xor_si128(state_index_13, _mm_slli_epi32(state_index_13, 15));
    __m128i z1      = _mm_xor_si128(left, right);
    __m128i z2      = _mm_xor_si128(state_index_9, _mm_srli_epi32(state_index_9, 11));
    __m128i result0 = _mm_xor_si128(z1, z2);
    state[index]    = result0;

    __m128i result1 = _mm_xor_si128(state_index_15, _mm_slli_epi32(state_index_15, 2));
    result1         = _mm_xor_si128(result1, _mm_xor_si128(z1, _mm_slli_epi32(z1, 18)));
    result1         = _mm_xor_si128(result1, _mm_slli_epi32(z2, 28));
    result1         = _mm_xor_si128(result1, _mm_xor_si128(result0, _mm_and_si128(_mm_slli_epi32(result0, 5), kMix)));
    index           = index_15;
    state[index]    = result1;

    _mm_storeu_si128((__m128i *)result4, result1);
}

inline void RandomWELL512a_SSE2::GetDouble4(double *result4)
{
    unsigned unsigned_result[4];
    GetUnsigned4(unsigned_result);

    const double kToFloat = 2.32830643653869628906e-10;
    for (unsigned loop = 0; loop < 4; ++loop)
        result4[loop] = unsigned_result[loop] * kToFloat;
}

#endif // RANDOM_WELL512A_SSE2_H