극초음속 비행체 선두부 전자기유체역학(MHD) 열유속 능동 완화 및 플라즈마 홀 효과 서보 아키텍처 (.NET 9 C# SIMD)

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace ZeliDesk.Defense.Hypersonic
{
    /// <summary>
    /// 극초음속 비행체 선두부 MHD 열유속 능동 완화 및 홀 효과 제어 서보
    /// GC 제로 할당 ref struct 및 AVX-256 SIMD 가속화
    /// </summary>
    public ref struct HypersonicMhdHeatFluxServo
    {
        private readonly ReadOnlySpan<float> _plasmaConductivity; // 플라즈마 전기전도도 sigma (S/m)
        private readonly ReadOnlySpan<float> _flowVelocities;     // 국소 플라즈마 유속 u (m/s)
        private readonly ReadOnlySpan<float> _baselineHeatFlux;    // 미보정 기준 열유속 q0 (MW/m^2)
        private readonly Span<float> _attenuatedHeatFlux;         // MHD 완화 열유속 qw (MW/m^2)
        private readonly Span<float> _coilCurrentCommands;        // 전자석 여자 전류 지령값 (A)

        private readonly float _magneticFluxDensity;  // 유효 자속밀도 B (Tesla)
        private readonly float _gasDensity;           // 충격층 기체 밀도 rho (kg/m^3)
        private readonly float _charLength;           // 특성 노즈콘 반경 L (m)
        private readonly float _alphaMhd;             // MHD 감쇠 계수

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public HypersonicMhdHeatFluxServo(
            ReadOnlySpan<float> plasmaConductivity,
            ReadOnlySpan<float> flowVelocities,
            ReadOnlySpan<float> baselineHeatFlux,
            Span<float> attenuatedHeatFlux,
            Span<float> coilCurrentCommands,
            float magneticFluxDensity = 1.4f,
            float gasDensity = 0.085f,
            float charLength = 0.05f,
            float alphaMhd = 0.85f)
        {
            _plasmaConductivity = plasmaConductivity;
            _flowVelocities = flowVelocities;
            _baselineHeatFlux = baselineHeatFlux;
            _attenuatedHeatFlux = attenuatedHeatFlux;
            _coilCurrentCommands = coilCurrentCommands;
            _magneticFluxDensity = magneticFluxDensity;
            _gasDensity = gasDensity;
            _charLength = charLength;
            _alphaMhd = alphaMhd;
        }

        /// <summary>
        /// 노즈콘 표면 격자별 MHD 감쇠율 및 전자석 코일 지령을 SIMD 8개 병렬 연산
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveOptimization)]
        public void ProcessMhdCoolingLoop()
        {
            int length = _plasmaConductivity.Length;
            int simdLength = length - (length % 8);

            float bSquared = _magneticFluxDensity * _magneticFluxDensity;
            Vector256<float> vBSq = Vector256.Create(bSquared);
            Vector256<float> vL = Vector256.Create(_charLength);
            Vector256<float> vRho = Vector256.Create(_gasDensity);
            Vector256<float> vAlpha = Vector256.Create(_alphaMhd);
            Vector256<float> vOne = Vector256.Create(1.0f);
            Vector256<float> vCurrentBase = Vector256.Create(250.0f);

            int i = 0;
            if (Avx2.IsSupported)
            {
                for (; i < simdLength; i += 8)
                {
                    Vector256<float> vSigma = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_plasmaConductivity.Slice(i, 8))[0]);
                    Vector256<float> vU = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_flowVelocities.Slice(i, 8))[0]);
                    Vector256<float> vQ0 = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_baselineHeatFlux.Slice(i, 8))[0]);

                    // 분모: rho * u
                    Vector256<float> vDenom = Avx.Multiply(vRho, vU);

                    // 스튜어트 수 N = (sigma * B^2 * L) / (rho * u)
                    Vector256<float> vNum = Avx.Multiply(Avx.Multiply(vSigma, vBSq), vL);
                    Vector256<float> vN = Avx.Divide(vNum, vDenom);

                    // 완화 계수: Phi = 1 / sqrt(1 + alpha * N)
                    Vector256<float> vTerm = Avx.Add(vOne, Avx.Multiply(vAlpha, vN));
                    Vector256<float> vSqrt = Avx.Sqrt(vTerm);
                    Vector256<float> vPhi = Avx.Divide(vOne, vSqrt);

                    // 완화된 열유속 qw = q0 * Phi
                    Vector256<float> vQw = Avx.Multiply(vQ0, vPhi);

                    // 전자석 여자 전류 지령 = CurrentBase * (1.0 + 0.5 * N)
                    Vector256<float> vIcoil = Avx.Multiply(vCurrentBase, Avx.Add(vOne, Avx.Multiply(vN, Vector256.Create(0.5f))));

                    vQw.CopyTo(_attenuatedHeatFlux.Slice(i, 8));
                    vIcoil.CopyTo(_coilCurrentCommands.Slice(i, 8));
                }
            }

            for (; i < length; i++)
            {
                float num = _plasmaConductivity[i] * bSquared * _charLength;
                float denom = _gasDensity * _flowVelocities[i];
                float n = num / MathF.Max(1e-3f, denom);
                float phi = 1.0f / MathF.Sqrt(1.0f + (_alphaMhd * n));
                _attenuatedHeatFlux[i] = _baselineHeatFlux[i] * phi;
                _coilCurrentCommands[i] = 250.0f * (1.0f + (0.5f * n));
            }
        }
    }
}