arch/AVX/RandUtils.h

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#ifndef EIGENRAND_RAND_UTILS_AVX_H
#define EIGENRAND_RAND_UTILS_AVX_H
 
#include <immintrin.h>
 
namespace Eigen
{
    namespace internal
    {
        template<typename Rng>
        struct RawbitsMaker<Packet4i, Rng, Packet8i, Rand::RandomEngineType::packet>
        {
            EIGEN_STRONG_INLINE Packet4i rawbits(Rng& rng)
            {
                return rng.half();
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_34(Rng& rng)
            {
                return rng.half();
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                return rng.half();
            }
        };
 
        template<typename Rng>
        struct RawbitsMaker<Packet8i, Rng, Packet4i, Rand::RandomEngineType::packet>
        {
            EIGEN_STRONG_INLINE Packet8i rawbits(Rng& rng)
            {
                return _mm256_insertf128_si256(_mm256_castsi128_si256(rng()), rng(), 1);
            }
 
            EIGEN_STRONG_INLINE Packet8i rawbits_34(Rng& rng)
            {
                return _mm256_insertf128_si256(_mm256_castsi128_si256(rng()), rng(), 1);
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                return rng();
            }
        };
 
        template<typename Rng, typename RngResult>
        struct RawbitsMaker<Packet8i, Rng, RngResult, Rand::RandomEngineType::scalar>
        {
            EIGEN_STRONG_INLINE Packet8i rawbits(Rng& rng)
            {
                if (sizeof(decltype(rng())) == 8)
                {
                    return _mm256_set_epi64x(rng(), rng(), rng(), rng());
                }
                else
                {
                    return _mm256_set_epi32(rng(), rng(), rng(), rng(),
                        rng(), rng(), rng(), rng());
                }
            }
 
            EIGEN_STRONG_INLINE Packet8i rawbits_34(Rng& rng)
            {
                Packet8i p;
                if (sizeof(decltype(rng())) == 8)
                {
#ifdef EIGEN_VECTORIZE_AVX2
                    p = _mm256_setr_epi64x(rng(), rng(), rng(), 0);
                    p = _mm256_permutevar8x32_epi32(p, _mm256_setr_epi32(0, 1, 2, 7, 3, 4, 5, 7));
                    p = _mm256_shuffle_epi8(p, _mm256_setr_epi8(
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11,
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11
                    ));
 
#else
                    auto v = rng();
                    p = _mm256_setr_epi64x(rng(), v, rng(), v >> 32);
                    Packet4i p1, p2, o = _mm_setr_epi8(
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11);
                    split_two(p, p1, p2);
                    p = combine_two(_mm_shuffle_epi8(p1, o), _mm_shuffle_epi8(p2, o));
#endif
                }
                else
                {
                    p = _mm256_setr_epi32(rng(), rng(), rng(), 0, rng(), rng(), rng(), 0);
#ifdef EIGEN_VECTORIZE_AVX2
                    p = _mm256_shuffle_epi8(p, _mm256_setr_epi8(
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11,
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11
                    ));
#else
                    Packet4i p1, p2, o = _mm_setr_epi8(
                        0, 1, 2, 3,
                        4, 5, 6, 7,
                        8, 9, 10, 11,
                        3, 7, 11, 11);
                    split_two(p, p1, p2);
                    p = combine_two(_mm_shuffle_epi8(p1, o), _mm_shuffle_epi8(p2, o));
#endif
                }
                return p;
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                if (sizeof(decltype(rng())) == 8)
                {
                    return _mm_set_epi64x(rng(), rng());
                }
                else
                {
                    return _mm_set_epi32(rng(), rng(), rng(), rng());
                }
            }
        };
 
        template<typename Rng>
        struct RawbitsMaker<Packet8i, Rng, Packet8i, Rand::RandomEngineType::packet>
        {
            EIGEN_STRONG_INLINE Packet8i rawbits(Rng& rng)
            {
                return rng();
            }
 
            EIGEN_STRONG_INLINE Packet8i rawbits_34(Rng& rng)
            {
                return rng();
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                return rng.half();
            }
        };
 
#ifndef EIGEN_VECTORIZE_AVX2
        template<>
        EIGEN_STRONG_INLINE Packet8f bit_to_ur_float<Packet8i>(const Packet8i& x)
        {
            const Packet4i lower = pset1<Packet4i>(0x7FFFFF),
                upper = pset1<Packet4i>(127 << 23);
            const Packet8f one = pset1<Packet8f>(1);
 
            Packet4i x1, x2;
            split_two(x, x1, x2);
 
            return psub(reinterpret_to_float(
                combine_two(por(pand(x1, lower), upper), por(pand(x2, lower), upper)
                )), one);
        }
 
        template<>
        EIGEN_STRONG_INLINE Packet4d bit_to_ur_double<Packet8i>(const Packet8i& x)
        {
            const Packet4i lower = pseti64<Packet4i>(0xFFFFFFFFFFFFFull),
                upper = pseti64<Packet4i>(1023ull << 52);
            const Packet4d one = pset1<Packet4d>(1);
 
            Packet4i x1, x2;
            split_two(x, x1, x2);
 
            return psub(reinterpret_to_double(
                combine_two(por(pand(x1, lower), upper), por(pand(x2, lower), upper)
                )), one);
        }
#endif
 
        template<typename Rng>
        struct UniformRealUtils<Packet8f, Rng> : public RawbitsMaker<Packet8i, Rng>
        {
            EIGEN_STRONG_INLINE Packet8f zero_to_one(Rng& rng)
            {
                return pdiv(_mm256_cvtepi32_ps(pand(this->rawbits(rng), pset1<Packet8i>(0x7FFFFFFF))),
                    pset1<Packet8f>(0x7FFFFFFF));
            }
 
            EIGEN_STRONG_INLINE Packet8f uniform_real(Rng& rng)
            {
                return bit_to_ur_float(this->rawbits_34(rng));
            }
        };
 
        template<typename Rng>
        struct UniformRealUtils<Packet4d, Rng> : public RawbitsMaker<Packet8i, Rng>
        {
            EIGEN_STRONG_INLINE Packet4d zero_to_one(Rng& rng)
            {
                return pdiv(_mm256_cvtepi32_pd(pand(this->rawbits_half(rng), pset1<Packet4i>(0x7FFFFFFF))),
                    pset1<Packet4d>(0x7FFFFFFF));
            }
 
            EIGEN_STRONG_INLINE Packet4d uniform_real(Rng& rng)
            {
                return bit_to_ur_double(this->rawbits(rng));
            }
        };
    }
}
#endif