#pragma once
#include <cstdint>
#include <cmath>
#include <cstring>
#include <vector>
#include <thread>
#include <algorithm>
#include <functional>
#include <cstdio>
#include <cstdlib>

namespace xt {

struct Rng {
    uint64_t s0, s1;
    explicit Rng(uint64_t seed = 0x853c49e6748fea9bULL) {
        s0 = seed ? seed : 0x9E3779B97F4A7C15ULL;
        s1 = seed * 6364136223846793005ULL + 1442695040888963407ULL;
        for (int i = 0; i < 16; ++i) next_u64();
    }
    uint64_t next_u64() {
        uint64_t x = s0, y = s1;
        s0 = y;
        x ^= x << 23;
        s1 = x ^ y ^ (x >> 17) ^ (y >> 26);
        return s1 + y;
    }
    uint32_t next_u32() { return (uint32_t)(next_u64() >> 32); }
    float uniform() { return (next_u32() >> 8) * (1.0f / 16777216.0f); }  // [0,1)
    float normal() {                       // Бокс–Мюллер
        float u1 = uniform();
        if (u1 < 1e-7f) u1 = 1e-7f;
        float u2 = uniform();
        return std::sqrt(-2.0f * std::logf(u1)) * std::cosf(6.28318530718f * u2);
    }
    size_t below(size_t n) { return n ? (size_t)(next_u64() % n) : 0; }
};

inline int& hw_threads() {
    static int t = [] {
        unsigned hc = std::thread::hardware_concurrency();
        if (hc == 0) hc = 1;
        if (hc > 16) hc = 16;
        return (int)hc;
    }();
    return t;
}
inline void set_threads(int n) { hw_threads() = n < 1 ? 1 : (n > 64 ? 64 : n); }

inline void parallel_for(int n, const std::function<void(int, int)>& fn) {
    if (n <= 0) return;
    int nt = hw_threads();
    if (n < nt * 8 || nt == 1) { fn(0, n); return; }
    std::vector<std::thread> th;
    th.reserve(nt);
    int chunk = (n + nt - 1) / nt;
    for (int t = 0; t < nt; ++t) {
        int b = t * chunk;
        int e = std::min(n, b + chunk);
        if (b >= e) break;
        th.emplace_back([=] { fn(b, e); });
    }
    for (auto& x : th) x.join();
}

struct Tensor {
    int rows = 0, cols = 0;
    std::vector<float> d;

    Tensor() {}
    Tensor(int r, int c) : rows(r), cols(c), d((size_t)r * c, 0.0f) {}

    void resize(int r, int c) { rows = r; cols = c; d.assign((size_t)r * c, 0.0f); }
    void resize3d(int h, int r, int c) { rows = r; cols = c; d.assign((size_t)h * r * c, 0.0f); }
    void zero() { std::fill(d.begin(), d.end(), 0.0f); }
    int  R() const { return rows; }
    int  C() const { return cols; }
    size_t n() const { return d.size(); }
    float*       ptr()       { return d.data(); }
    const float* ptr() const { return d.data(); }
    float&  at(int i)       { return d[(size_t)i]; }
    float   at(int i) const { return d[(size_t)i]; }
    float&  operator()(int r, int c)       { return d[(size_t)r * cols + c]; }
    float   operator()(int r, int c) const { return d[(size_t)r * cols + c]; }
    float*       row(int r)       { return d.data() + (size_t)r * cols; }
    const float* row(int r) const { return d.data() + (size_t)r * cols; }

    float L2() const {
        double s = 0;
        for (float x : d) s += (double)x * x;
        return (float)std::sqrt(s);
    }
    float maxAbs() const {
        float m = 0;
        for (float x : d) m = std::max(m, std::fabs(x));
        return m;
    }
};

inline void gemm_nn(const Tensor& A, const Tensor& B, Tensor& C) {
    const int N = A.R(), K = A.C(), M = B.C();
    C.resize(N, M);
    parallel_for(N, [&](int i0, int i1) {
        for (int i = i0; i < i1; ++i) {
            const float* ar = A.row(i);
            float* cr = C.row(i);
            for (int k = 0; k < K; ++k) {
                float a = ar[k];
                if (a == 0.0f) continue;
                const float* br = B.row(k);
                for (int j = 0; j < M; ++j) cr[j] += a * br[j];
            }
        }
    });
}

inline void gemm_nt(const Tensor& A, const Tensor& B, Tensor& C) {
    const int N = A.R(), K = A.C(), M = B.R();
    C.resize(N, M);
    parallel_for(N, [&](int i0, int i1) {
        for (int i = i0; i < i1; ++i) {
            const float* ar = A.row(i);
            float* cr = C.row(i);
            for (int j = 0; j < M; ++j) {
                const float* br = B.row(j);
                float s = 0.0f;
                for (int k = 0; k < K; ++k) s += ar[k] * br[k];
                cr[j] = s;
            }
        }
    });
}

inline void gemm_tn(const Tensor& A, const Tensor& B, Tensor& C, bool accumulate = false) {
    const int N = A.R(), K = A.C(), M = B.C();
    if (!accumulate) {
        C.resize(K, M);
    } else {
        if (C.R() != K || C.C() != M) {
            std::fprintf(stderr,
                         "gemm_tn: форма C %dx%d != ожидаемой %dx%d "
                         "(A %dx%d, B %dx%d)\n",
                         C.R(), C.C(), K, M, A.R(), A.C(), B.R(), B.C());
            std::abort();
        }
    }
    parallel_for(K, [&](int k0, int k1) {
        for (int k = k0; k < k1; ++k) {
            float* cr = C.row(k);
            for (int i = 0; i < N; ++i) {
                float a = A.at((size_t)i * K + k);
                if (a == 0.0f) continue;
                const float* br = B.row(i);
                for (int j = 0; j < M; ++j) cr[j] += a * br[j];
            }
        }
    });
}

inline float silu(float x) { return x / (1.0f + std::expf(-x)); }
inline float dsilu(float x) {
    float s = 1.0f / (1.0f + std::expf(-x));
    return s * (1.0f + x * (1.0f - s));
}

inline void rmsnorm_forward(const Tensor& x, const Tensor& w, float eps,
                            Tensor& y, Tensor& inv_rms) {
    const int N = x.R(), D = x.C();
    y.resize(N, D);
    inv_rms.resize(N, 1);
    for (int n = 0; n < N; ++n) {
        const float* xr = x.row(n);
        float ss = 0.0f;
        for (int j = 0; j < D; ++j) ss += xr[j] * xr[j];
        float r = 1.0f / std::sqrtf(ss / D + eps);
        inv_rms.at(n) = r;
        float* yr = y.row(n);
        for (int j = 0; j < D; ++j) yr[j] = xr[j] * r * w.at(j);
    }
}

inline void rmsnorm_backward(const Tensor& x, const Tensor& w, const Tensor& inv_rms,
                             const Tensor& dy, Tensor& dx, Tensor& dw) {
    const int N = x.R(), D = x.C();
    dx.resize(N, D);
    dw.resize(1, D);
    dw.zero();
    for (int n = 0; n < N; ++n) {
        const float* xr = x.row(n);
        const float* dr = dy.row(n);
        float* gx = dx.row(n);
        const float r = inv_rms.at(n);
        float s = 0.0f;
        for (int j = 0; j < D; ++j) s += dr[j] * w.at(j) * xr[j];
        for (int j = 0; j < D; ++j) {
            gx[j] = r * dr[j] * w.at(j) - r * r * r * s * xr[j] / (float)D;
            dw.at(j) += dr[j] * xr[j] * r;
        }
    }
}

}