arch/NEON/RandUtils.h

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#ifndef EIGENRAND_RAND_UTILS_NEON_H
#define EIGENRAND_RAND_UTILS_NEON_H
 
#include <arm_neon.h>
 
namespace Eigen
{
    namespace internal
    {
        template<typename Rng, typename RngResult>
        struct RawbitsMaker<Packet4i, Rng, RngResult, Rand::RandomEngineType::scalar_fullbit>
        {
            EIGEN_STRONG_INLINE Packet4i rawbits(Rng& rng)
            {
                if (sizeof(RngResult) == 8)
                {
                    uint64_t v[2];
                    v[0] = rng();
                    v[1] = rng();
                    return vld1q_s32((int32_t*)v);
                }
                else
                {
                    uint32_t v[4];
                    v[0] = rng();
                    v[1] = rng();
                    v[2] = rng();
                    v[3] = rng();
                    return vld1q_s32((int32_t*)v);
                }
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_34(Rng& rng)
            {
                if (sizeof(RngResult) == 8)
                {
                    uint64_t v[2];
                    v[0] = rng();
                    v[1] = rng();
                    return vld1q_s32((int32_t*)v);
                }
                else
                {
                    uint32_t v[4];
                    v[0] = rng();
                    v[1] = rng();
                    v[2] = rng();
                    v[3] = rng();
                    return vld1q_s32((int32_t*)v);
                }
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                if (sizeof(decltype(rng())) == 8)
                {
                    uint64_t v[2];
                    v[0] = rng();
                    v[1] = 0;
                    return vld1q_s32((int32_t*)v);
                }
                else
                {
                    uint32_t v[4];
                    v[0] = rng();
                    v[1] = rng();
                    v[2] = 0;
                    v[3] = 0;
                    return vld1q_s32((int32_t*)v);
                }
            }
        };
 
        template<typename Rng>
        struct RawbitsMaker<Packet4i, Rng, Packet4i, Rand::RandomEngineType::packet>
        {
            EIGEN_STRONG_INLINE Packet4i rawbits(Rng& rng)
            {
                return rng();
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_34(Rng& rng)
            {
                return rng();
            }
 
            EIGEN_STRONG_INLINE Packet4i rawbits_half(Rng& rng)
            {
                return rng();
            }
        };
 
        template<typename Rng>
        struct UniformRealUtils<Packet4f, Rng> : public RawbitsMaker<Packet4i, Rng>
        {
            EIGEN_STRONG_INLINE Packet4f zero_to_one(Rng& rng)
            {
                return pdiv((Packet4f)vcvtq_f32_s32(pand(this->rawbits(rng), pset1<Packet4i>(0x7FFFFFFF))),
                    pset1<Packet4f>(0x7FFFFFFF));
            }
 
            EIGEN_STRONG_INLINE Packet4f uniform_real(Rng& rng)
            {
                return bit_to_ur_float(this->rawbits_34(rng));
            }
        };
 
#if EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
        template<typename Rng>
        struct UniformRealUtils<Packet2d, Rng> : public RawbitsMaker<Packet4i, Rng>
        {
            EIGEN_STRONG_INLINE Packet2d zero_to_one(Rng& rng)
            {
                return pdiv((Packet2d)vcvtq_f64_s64(vreinterpretq_s64_s32(pand(this->rawbits(rng), vreinterpretq_s32_s64(vdupq_n_s64(0x7FFFFFFF))))),
                    pset1<Packet2d>(0x7FFFFFFF));
            }
 
            EIGEN_STRONG_INLINE Packet2d uniform_real(Rng& rng)
            {
                return bit_to_ur_double(this->rawbits(rng));
            }
        };
 
#else
        template<typename Gen, typename Urng, bool _mutable>
        struct functor_traits<scalar_rng_adaptor<Gen, double, Urng, _mutable> >
        {
            enum { Cost = HugeCost, PacketAccess = 0, IsRepeatable = false };
        };
#endif
    }
}
#endif