//
// V5 mining kernel โ€” sequential multi-nonce per thread.
//
// Each thread processes K nonces SEQUENTIALLY (one after another), not
// interleaved. At any moment only one nonce's state is live, so per-thread
// register pressure is identical to V1. Benefits:
//   - Amortizes per-dispatch overhead (smaller grids)
//   - Reduces SIMD divergence at the tail
//   - Better instruction cache reuse across iterations
//
// K is a compile-time constant. K=4 is conservative; bigger K trades
// per-thread idle time at the count boundary for less dispatch overhead.
//

#include <metal_stdlib>
using namespace metal;

constant ulong IV0 = 0x6a09e667f3bcc908UL;
constant ulong IV1 = 0xbb67ae8584caa73bUL;
constant ulong IV2 = 0x3c6ef372fe94f82bUL;
constant ulong IV3 = 0xa54ff53a5f1d36f1UL;
constant ulong IV4 = 0x510e527fade682d1UL;
constant ulong IV5 = 0x9b05688c2b3e6c1fUL;
constant ulong IV6 = 0x1f83d9abfb41bd6bUL;
constant ulong IV7 = 0x5be0cd19137e2179UL;

constant uint NONCES_PER_THREAD = 4;

struct Params {
    uchar  m[32];
    ulong  n;
    ulong  nonce_base;
    uint   count;
    uint   _pad;
};

static inline ulong rotr64(ulong x, uint n) {
    return (x >> n) | (x << (64 - n));
}

#define G(va, vb, vc, vd, x, y) do {                              \
    va = va + vb + (x);                                           \
    vd = rotr64(vd ^ va, 32);                                     \
    vc = vc + vd;                                                 \
    vb = rotr64(vb ^ vc, 24);                                     \
    va = va + vb + (y);                                           \
    vd = rotr64(vd ^ va, 16);                                     \
    vc = vc + vd;                                                 \
    vb = rotr64(vb ^ vc, 63);                                     \
} while (0)

#define R12(m,                                                    \
            s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,sa,sb,sc,sd,se,sf,      \
            v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF) do { \
    G(v0, v4, v8,  vC, m[s0], m[s1]);                             \
    G(v1, v5, v9,  vD, m[s2], m[s3]);                             \
    G(v2, v6, vA,  vE, m[s4], m[s5]);                             \
    G(v3, v7, vB,  vF, m[s6], m[s7]);                             \
    G(v0, v5, vA,  vF, m[s8], m[s9]);                             \
    G(v1, v6, vB,  vC, m[sa], m[sb]);                             \
    G(v2, v7, v8,  vD, m[sc], m[sd]);                             \
    G(v3, v4, v9,  vE, m[se], m[sf]);                             \
} while (0)

static inline void blake2b256_block(thread ulong* m, uint t_bytes, thread ulong* h_out) {
    ulong v0 = IV0 ^ 0x01010020UL;
    ulong v1 = IV1, v2 = IV2, v3 = IV3, v4 = IV4, v5 = IV5, v6 = IV6, v7 = IV7;
    ulong v8 = IV0, v9 = IV1, vA = IV2, vB = IV3;
    ulong vC = IV4 ^ (ulong)t_bytes, vD = IV5;
    ulong vE = IV6 ^ 0xFFFFFFFFFFFFFFFFUL, vF = IV7;

    R12(m,  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 14,10, 4, 8, 9,15,13, 6, 1,12, 0, 2,11, 7, 5, 3, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 11, 8,12, 0, 5, 2,15,13,10,14, 3, 6, 7, 1, 9, 4, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m,  7, 9, 3, 1,13,12,11,14, 2, 6, 5,10, 4, 0,15, 8, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m,  9, 0, 5, 7, 2, 4,10,15,14, 1,11,12, 6, 8, 3,13, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m,  2,12, 6,10, 0,11, 8, 3, 4,13, 7, 5,15,14, 1, 9, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 12, 5, 1,15,14,13, 4,10, 0, 7, 6, 3, 9, 2, 8,11, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 13,11, 7,14,12, 1, 3, 9, 5, 0,15, 4, 8, 6, 2,10, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m,  6,15,14, 9,11, 3, 0, 8,12, 2,13, 7, 1, 4,10, 5, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 10, 2, 8, 4, 7, 6, 1, 5,15,11, 9,14, 3,12,13, 0, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m,  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);
    R12(m, 14,10, 4, 8, 9,15,13, 6, 1,12, 0, 2,11, 7, 5, 3, v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,vA,vB,vC,vD,vE,vF);

    h_out[0] = (IV0 ^ 0x01010020UL) ^ v0 ^ v8;
    h_out[1] =  IV1                  ^ v1 ^ v9;
    h_out[2] =  IV2                  ^ v2 ^ vA;
    h_out[3] =  IV3                  ^ v3 ^ vB;
}

static inline void add256_v4(thread ulong* sum, ulong4 r) {
    ulong t = sum[0] + r.x;
    ulong c = (t < sum[0]) ? 1UL : 0UL;
    sum[0] = t;
    t = sum[1] + r.y;
    ulong c1 = (t < sum[1]) ? 1UL : 0UL;
    ulong t2 = t + c;
    ulong c2 = (t2 < t) ? 1UL : 0UL;
    sum[1] = t2;
    c = c1 + c2;
    t = sum[2] + r.z;
    c1 = (t < sum[2]) ? 1UL : 0UL;
    t2 = t + c;
    c2 = (t2 < t) ? 1UL : 0UL;
    sum[2] = t2;
    c = c1 + c2;
    t = sum[3] + r.w;
    t2 = t + c;
    sum[3] = t2;
}

// Process a single nonce. Caller passes shared per-thread m_blk template
// (with the 32-byte header pre-packed); this function writes nonce into
// slot 4 and runs the full mining work.
static inline void mine_one_nonce(
    thread ulong* m_blk_template,    // m[0..4] = header, m[4..16] = zero
    ulong nonce,
    device const ulong4* R,
    ulong N,
    thread ulong* d_out               // 4 ulongs of d hash
) {
    ulong m_blk[16];
    m_blk[0] = m_blk_template[0];
    m_blk[1] = m_blk_template[1];
    m_blk[2] = m_blk_template[2];
    m_blk[3] = m_blk_template[3];
    m_blk[4] = nonce;
    m_blk[5]=0; m_blk[6]=0; m_blk[7]=0; m_blk[8]=0; m_blk[9]=0;
    m_blk[10]=0; m_blk[11]=0; m_blk[12]=0; m_blk[13]=0; m_blk[14]=0; m_blk[15]=0;

    ulong seed_h[4];
    blake2b256_block(m_blk, 40u, seed_h);

    ulong eb0 = seed_h[0], eb1 = seed_h[1], eb2 = seed_h[2], eb3 = seed_h[3];
    ulong eb4 = seed_h[0] & 0xFFFFFFUL;

    #define SBYTE5(k) (\
        ((k) <  8) ? ((eb0 >> ((k)      * 8)) & 0xFFUL) :  \
        ((k) < 16) ? ((eb1 >> (((k)-8)  * 8)) & 0xFFUL) :  \
        ((k) < 24) ? ((eb2 >> (((k)-16) * 8)) & 0xFFUL) :  \
        ((k) < 32) ? ((eb3 >> (((k)-24) * 8)) & 0xFFUL) :  \
                     ((eb4 >> (((k)-32) * 8)) & 0xFFUL) )

    #define IDX5(i) ((ulong)((uint)((SBYTE5(i  ) << 24) |  \
                                   (SBYTE5(i+1) << 16) |  \
                                   (SBYTE5(i+2) <<  8) |  \
                                    SBYTE5(i+3))) % N)

    ulong sum[4] = {0,0,0,0};
    #define LOAD5(i) add256_v4(sum, R[IDX5(i)])
    LOAD5( 0); LOAD5( 1); LOAD5( 2); LOAD5( 3);
    LOAD5( 4); LOAD5( 5); LOAD5( 6); LOAD5( 7);
    LOAD5( 8); LOAD5( 9); LOAD5(10); LOAD5(11);
    LOAD5(12); LOAD5(13); LOAD5(14); LOAD5(15);
    LOAD5(16); LOAD5(17); LOAD5(18); LOAD5(19);
    LOAD5(20); LOAD5(21); LOAD5(22); LOAD5(23);
    LOAD5(24); LOAD5(25); LOAD5(26); LOAD5(27);
    LOAD5(28); LOAD5(29); LOAD5(30); LOAD5(31);

    ulong sum_blk[16] = {sum[0],sum[1],sum[2],sum[3], 0,0,0,0, 0,0,0,0, 0,0,0,0};
    blake2b256_block(sum_blk, 32u, d_out);

    #undef SBYTE5
    #undef IDX5
    #undef LOAD5
}

kernel void mine_kernel_v5(
    device   const ulong4*     R          buffer(0),
    device   atomic_uint*      acc        buffer(1),
    constant Params&           p          buffer(2),
    uint                       gid        thread_position_in_grid
) {
    uint base_nonce_idx = gid * NONCES_PER_THREAD;
    if (base_nonce_idx >= p.count) return;

    // Pack m once per thread, reuse across the K nonces.
    ulong m_template[5];
    m_template[0] = ((ulong)p.m[ 0]) | ((ulong)p.m[ 1] <<  8) | ((ulong)p.m[ 2] << 16) | ((ulong)p.m[ 3] << 24)
                  | ((ulong)p.m[ 4] << 32) | ((ulong)p.m[ 5] << 40) | ((ulong)p.m[ 6] << 48) | ((ulong)p.m[ 7] << 56);
    m_template[1] = ((ulong)p.m[ 8]) | ((ulong)p.m[ 9] <<  8) | ((ulong)p.m[10] << 16) | ((ulong)p.m[11] << 24)
                  | ((ulong)p.m[12] << 32) | ((ulong)p.m[13] << 40) | ((ulong)p.m[14] << 48) | ((ulong)p.m[15] << 56);
    m_template[2] = ((ulong)p.m[16]) | ((ulong)p.m[17] <<  8) | ((ulong)p.m[18] << 16) | ((ulong)p.m[19] << 24)
                  | ((ulong)p.m[20] << 32) | ((ulong)p.m[21] << 40) | ((ulong)p.m[22] << 48) | ((ulong)p.m[23] << 56);
    m_template[3] = ((ulong)p.m[24]) | ((ulong)p.m[25] <<  8) | ((ulong)p.m[26] << 16) | ((ulong)p.m[27] << 24)
                  | ((ulong)p.m[28] << 32) | ((ulong)p.m[29] << 40) | ((ulong)p.m[30] << 48) | ((ulong)p.m[31] << 56);
    m_template[4] = 0UL;

    for (uint k = 0; k < NONCES_PER_THREAD; k++) {
        uint nonce_idx = base_nonce_idx + k;
        if (nonce_idx >= p.count) return;
        ulong nonce = p.nonce_base + (ulong)nonce_idx;

        ulong d[4];
        mine_one_nonce(m_template, nonce, R, p.n, d);

        atomic_fetch_xor_explicit(&acc[0], (uint)(d[0] & 0xFFFFFFFFUL), memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[1], (uint)(d[0] >> 32),          memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[2], (uint)(d[1] & 0xFFFFFFFFUL), memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[3], (uint)(d[1] >> 32),          memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[4], (uint)(d[2] & 0xFFFFFFFFUL), memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[5], (uint)(d[2] >> 32),          memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[6], (uint)(d[3] & 0xFFFFFFFFUL), memory_order_relaxed);
        atomic_fetch_xor_explicit(&acc[7], (uint)(d[3] >> 32),          memory_order_relaxed);
    }
}

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