ckernel_quant.h

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/**
 * @file ckernel_quant.h
 * @brief Quantization block structures for weight-only quantization
 *
 * Defines block structures for various quantization formats used in LLM inference.
 * Primary focus on Q4_K_M which is commonly used for LLM weight compression.
 *
 * Block structures are compatible with llama.cpp/GGML for model loading.
 */
 
#ifndef CKERNEL_QUANT_H
#define CKERNEL_QUANT_H
 
#include <stdint.h>
#include <stddef.h>
#include "ckernel_dtype.h"
 
#ifdef __cplusplus
extern "C" {
#endif
 
/* ============================================================================
 * Half-Precision Type (FP16 - IEEE 754)
 * ============================================================================ */
 
typedef uint16_t ck_half;
 
/* ============================================================================
 * Q4_0: Simple 4-bit Quantization
 * - 32 weights per block
 * - 1 FP16 scale per block
 * - 18 bytes per 32 weights = 4.5 bits/weight
 * ============================================================================ */
 
#define QK4_0 32
 
typedef struct {
    ck_half d;             /* 2 bytes: scale (delta) */
    uint8_t qs[QK4_0 / 2]; /* 16 bytes: 32 x 4-bit weights (2 per byte) */
} block_q4_0;
/* Total: 18 bytes per 32 weights */
 
/* ============================================================================
 * Q4_1: Simple 4-bit Quantization with Min
 * - 32 weights per block
 * - 2 FP16 values: scale (d) and min (m)
 * - 20 bytes per 32 weights = 5.0 bits/weight
 * ============================================================================ */
 
#define QK4_1 32
 
typedef struct {
    ck_half d;             /* 2 bytes: scale (delta) */
    ck_half m;             /* 2 bytes: minimum */
    uint8_t qs[QK4_1 / 2]; /* 16 bytes: 32 x 4-bit weights (2 per byte) */
} block_q4_1;
/* Total: 20 bytes per 32 weights */
 
/* ============================================================================
 * Q5_0: Simple 5-bit Quantization
 * - 32 weights per block
 * - 1 FP16 scale per block
 * - Low 4 bits stored like Q4_0, high 1 bit packed separately
 * - 22 bytes per 32 weights = 5.5 bits/weight
 * ============================================================================ */
 
#define QK5_0 32
 
typedef struct {
    ck_half d;             /* 2 bytes: scale (delta) */
    uint8_t qh[4];         /* 4 bytes: high 1-bit of each weight (32 bits total) */
    uint8_t qs[QK5_0 / 2]; /* 16 bytes: low 4-bits of 32 weights (2 per byte) */
} block_q5_0;
/* Total: 22 bytes per 32 weights */
 
/* ============================================================================
 * Q5_1: Simple 5-bit Quantization with Min
 * - 32 weights per block
 * - 2 FP16 values: scale (d) and min (m)
 * - Low 4 bits stored like Q4_1, high 1 bit packed separately
 * - 24 bytes per 32 weights = 6.0 bits/weight
 * ============================================================================ */
 
#define QK5_1 32
 
typedef struct {
    ck_half d;             /* 2 bytes: scale (delta) */
    ck_half m;             /* 2 bytes: minimum */
    uint8_t qh[4];         /* 4 bytes: high 1-bit of each weight (32 bits total) */
    uint8_t qs[QK5_1 / 2]; /* 16 bytes: low 4-bits of 32 weights (2 per byte) */
} block_q5_1;
/* Total: 24 bytes per 32 weights */
 
/* ============================================================================
 * Q8_0: Simple 8-bit Quantization
 * - 32 weights per block
 * - 1 FP16 scale per block
 * - 34 bytes per 32 weights = 8.5 bits/weight
 * ============================================================================ */
 
#define QK8_0 32
 
typedef struct {
    ck_half d;             /* 2 bytes: scale */
    int8_t qs[QK8_0];      /* 32 bytes: 32 x 8-bit signed weights */
} block_q8_0;
/* Total: 34 bytes per 32 weights */
 
/* ============================================================================
 * Q4_K: K-Quant 4-bit with Nested Scales (Primary Target)
 * - 256 weights per super-block
 * - 8 sub-blocks of 32 weights each
 * - Two-level scaling: super-block FP16 + sub-block 6-bit
 * - 144 bytes per 256 weights = 4.5 bits/weight
 *
 * This is the format used by Q4_K_M, Q4_K_S, Q4_K_L variants.
 * The M/S/L suffix indicates quantization aggressiveness, not structure.
 * ============================================================================ */
 
#define QK_K 256
#define K_SCALE_SIZE 12
 
typedef struct {
    ck_half d;                    /* 2 bytes: super-block scale */
    ck_half dmin;                 /* 2 bytes: super-block minimum */
    uint8_t scales[K_SCALE_SIZE]; /* 12 bytes: 8 sub-block scales + 8 sub-block mins (6-bit packed) */
    uint8_t qs[QK_K / 2];         /* 128 bytes: 256 x 4-bit weights */
} block_q4_K;
/* Total: 144 bytes per 256 weights */
 
/* ============================================================================
 * Q5_K: K-Quant 5-bit with Nested Scales
 * - 256 weights per super-block
 * - 8 sub-blocks of 32 weights each
 * - Two-level scaling: super-block FP16 + sub-block 6-bit
 * - High bit per weight stored separately (1 bit each)
 * - 176 bytes per 256 weights = 5.5 bits/weight
 * ============================================================================ */
 
typedef struct {
    ck_half d;                    /* 2 bytes: super-block scale */
    ck_half dmin;                 /* 2 bytes: super-block minimum */
    uint8_t scales[K_SCALE_SIZE]; /* 12 bytes: 8 sub-block scales + 8 sub-block mins (6-bit packed) */
    uint8_t qh[QK_K / 8];         /* 32 bytes: high 1-bit for 256 weights */
    uint8_t qs[QK_K / 2];         /* 128 bytes: 256 x 4-bit weights */
} block_q5_K;
/* Total: 176 bytes per 256 weights */
 
/* ============================================================================
 * Q6_K: K-Quant 6-bit (per-16 scales)
 * - 256 weights per block
 * - 16 sub-blocks of 16 weights each
 * - Stored as low 4 bits (ql) + high 2 bits (qh) + int8 scales
 * ============================================================================ */
 
typedef struct {
    uint8_t ql[QK_K / 2];      /* 128 bytes: low 4 bits */
    uint8_t qh[QK_K / 4];      /* 64 bytes: high 2 bits */
    int8_t scales[QK_K / 16];  /* 16 bytes: 16 sub-block scales */
    ck_half d;                 /* 2 bytes: super-block scale */
} block_q6_K;
/* Total: 210 bytes per 256 weights */
 
/* ============================================================================
 * Q8_K: K-Quant 8-bit (used for activations in some ops)
 * - 256 weights per super-block
 * - 1 FP32 scale per block (not FP16 like others!)
 * ============================================================================ */
 
typedef struct {
    float d;                  /* 4 bytes: scale */
    int8_t qs[QK_K];          /* 256 bytes: 256 x 8-bit signed weights */
    int16_t bsums[QK_K / 16]; /* 32 bytes: block sums for optimization */
} block_q8_K;
/* Total: 292 bytes per 256 weights */
 
/* ============================================================================
 * Size Calculation Utilities
 * ============================================================================ */
 
/**
 * @brief Get the block size (number of weights per block) for a quant type
 */
static inline size_t ck_quant_block_size(int type) {
    switch (type) {
        case 0: return QK4_0;    /* Q4_0 */
        case 1: return QK8_0;    /* Q8_0 */
        case 2: return QK_K;     /* Q4_K */
        case 3: return QK_K;     /* Q8_K */
        case CK_DT_Q4_1: return QK4_1;
        case CK_DT_Q5_0: return QK5_0;
        case CK_DT_Q5_1: return QK5_1;
        case CK_DT_Q5_K: return QK_K;
        case CK_DT_Q6_K: return QK_K;
        default: return 1;
    }
}
 
/**
 * @brief Get the byte size per block for a quant type
 */
static inline size_t ck_quant_type_size(int type) {
    switch (type) {
        case 0: return sizeof(block_q4_0);
        case 1: return sizeof(block_q8_0);
        case 2: return sizeof(block_q4_K);
        case 3: return sizeof(block_q8_K);
        case CK_DT_Q4_1: return sizeof(block_q4_1);
        case CK_DT_Q5_0: return sizeof(block_q5_0);
        case CK_DT_Q5_1: return sizeof(block_q5_1);
        case CK_DT_Q5_K: return sizeof(block_q5_K);
        case CK_DT_Q6_K: return sizeof(block_q6_K);
        default: return 4; /* FP32 */
    }
}
 
/**
 * @brief Calculate total bytes needed for n_elements with given quant type
 */
static inline size_t ck_quant_row_size(int type, int64_t n_elements) {
    size_t block_size = ck_quant_block_size(type);
    size_t type_size = ck_quant_type_size(type);
    return (n_elements / block_size) * type_size;
}
 
/* ============================================================================
 * Q4_K Scale Unpacking Utilities
 *
 * The scales[12] array packs 8 scales and 8 mins in 6-bit format.
 * Unpacking is non-trivial due to the bit packing.
 * ============================================================================ */
 
/**
 * @brief Unpack Q4_K sub-block scales and mins
 *
 * @param scales The packed scales[12] array from block_q4_K
 * @param sc Output: 8 unpacked scale values (multiply by super-block d)
 * @param m Output: 8 unpacked min values (multiply by super-block dmin)
 *
 * This matches llama.cpp's get_scale_min_k4() function exactly.
 * The 12-byte scales array layout:
 *   - bytes 0-3: 6-bit scales[0-3] (high 2 bits used for scales[4-7])
 *   - bytes 4-7: 6-bit mins[0-3] (high 2 bits used for mins[4-7])
 *   - bytes 8-11: low 4 bits for scales[4-7], high 4 bits for mins[4-7]
 */
static inline void unpack_q4_k_scales(const uint8_t *scales,
                                       uint8_t *sc, uint8_t *m) {
    /* Direct 6-bit values for indices 0-3 */
    sc[0] = scales[0] & 0x3F;
    sc[1] = scales[1] & 0x3F;
    sc[2] = scales[2] & 0x3F;
    sc[3] = scales[3] & 0x3F;
 
    m[0] = scales[4] & 0x3F;
    m[1] = scales[5] & 0x3F;
    m[2] = scales[6] & 0x3F;
    m[3] = scales[7] & 0x3F;
 
    /* 6-bit values for indices 4-7: low 4 bits from bytes 8-11,
     * high 2 bits from upper bits of bytes 0-3 (scales) and 4-7 (mins) */
    sc[4] = (scales[8]  & 0x0F) | ((scales[0] >> 6) << 4);
    sc[5] = (scales[9]  & 0x0F) | ((scales[1] >> 6) << 4);
    sc[6] = (scales[10] & 0x0F) | ((scales[2] >> 6) << 4);
    sc[7] = (scales[11] & 0x0F) | ((scales[3] >> 6) << 4);
 
    m[4] = (scales[8]  >> 4) | ((scales[4] >> 6) << 4);
    m[5] = (scales[9]  >> 4) | ((scales[5] >> 6) << 4);
    m[6] = (scales[10] >> 4) | ((scales[6] >> 6) << 4);
    m[7] = (scales[11] >> 4) | ((scales[7] >> 6) << 4);
}
 
/**
 * @brief Unpack Q5_K sub-block scales and mins
 *
 * @param scales The packed scales[12] array from block_q5_K
 * @param sc Output: 8 unpacked scale values (multiply by super-block d)
 * @param m Output: 8 unpacked min values (multiply by super-block dmin)
 *
 * Q5_K uses the same 6-bit packed format as Q4_K for scales/mins.
 * The 12-byte scales array layout is identical:
 *   - bytes 0-3: 6-bit scales[0-3] (high 2 bits used for scales[4-7])
 *   - bytes 4-7: 6-bit mins[0-3] (high 2 bits used for mins[4-7])
 *   - bytes 8-11: low 4 bits for scales[4-7], high 4 bits for mins[4-7]
 */
static inline void unpack_q5_k_scales(const uint8_t *scales,
                                     uint8_t *sc, uint8_t *m) {
    /* Q5_K uses identical packing as Q4_K for scales/mins */
    unpack_q4_k_scales(scales, sc, m);
}
 
/* ============================================================================
 * FP16 Conversion Utilities
 *
 * Three variants:
 *   _soft  - Pure C bit manipulation (always available, portable)
 *   _simd  - F16C hardware instruction (vcvtph2ps/vcvtps2ph, Ivy Bridge+)
 *   (default) - Auto-dispatches to best available at compile time
 * ============================================================================ */
 
/**
 * @brief Convert FP16 (ck_half) to FP32 — software implementation
 */
static inline float ck_fp16_to_fp32_soft(ck_half h) {
    uint32_t sign = (h & 0x8000) << 16;
    uint32_t exp = (h >> 10) & 0x1F;
    uint32_t mant = h & 0x3FF;
 
    uint32_t result;
 
    if (exp == 0) {
        if (mant == 0) {
            result = sign;
        } else {
            /* Denormalized - convert to normalized FP32 */
            exp = 1;
            while ((mant & 0x400) == 0) {
                mant <<= 1;
                exp--;
            }
            mant &= 0x3FF;
            result = sign | ((exp + 127 - 15) << 23) | (mant << 13);
        }
    } else if (exp == 31) {
        result = sign | 0x7F800000 | (mant << 13);
    } else {
        result = sign | ((exp + 127 - 15) << 23) | (mant << 13);
    }
 
    union { uint32_t u; float f; } u;
    u.u = result;
    return u.f;
}
 
/**
 * @brief Convert FP32 to FP16 (ck_half) — software implementation
 */
static inline ck_half ck_fp32_to_fp16_soft(float f) {
    union { uint32_t u; float f; } u;
    u.f = f;
 
    uint32_t sign = (u.u >> 16) & 0x8000;
    int32_t exp = ((u.u >> 23) & 0xFF) - 127 + 15;
    uint32_t mant = (u.u >> 13) & 0x3FF;
 
    if (exp <= 0) {
        if (exp < -10) {
            return sign;
        }
        mant = (mant | 0x400) >> (1 - exp);
        return sign | mant;
    } else if (exp >= 31) {
        return sign | 0x7C00;
    }
 
    return sign | (exp << 10) | mant;
}
 
/* --------------------------------------------------------------------------
 * F16C Hardware SIMD conversion (requires Intel Ivy Bridge+ or AMD Piledriver+)
 * Uses vcvtsh2ss / vcvtss2sh single-element hardware instructions.
 * -------------------------------------------------------------------------- */
#if defined(__F16C__)
#include <immintrin.h>
 
/**
 * @brief Convert FP16 to FP32 — F16C hardware (1 instruction: vcvtsh2ss)
 */
static inline float ck_fp16_to_fp32_simd(ck_half h) {
    return _cvtsh_ss(h);
}
 
/**
 * @brief Convert FP32 to FP16 — F16C hardware (1 instruction: vcvtss2sh)
 */
static inline ck_half ck_fp32_to_fp16_simd(float f) {
    return (ck_half)_cvtss_sh(f, _MM_FROUND_TO_NEAREST_INT);
}
#endif /* __F16C__ */
 
/* --------------------------------------------------------------------------
 * Default dispatch: selects hardware SIMD when available, else software
 * -------------------------------------------------------------------------- */
static inline float ck_fp16_to_fp32(ck_half h) {
#if defined(__F16C__)
    return ck_fp16_to_fp32_simd(h);
#else
    return ck_fp16_to_fp32_soft(h);
#endif
}
 
static inline ck_half ck_fp32_to_fp16(float f) {
#if defined(__F16C__)
    return ck_fp32_to_fp16_simd(f);
#else
    return ck_fp32_to_fp16_soft(f);
#endif
}
 
/* Convenience macros */
#define CK_FP16_TO_FP32(x) ck_fp16_to_fp32(x)
#define CK_FP32_TO_FP16(x) ck_fp32_to_fp16(x)
#define CK_FP16_TO_FP32_SIMD(x) ck_fp16_to_fp32_simd(x)
#define CK_FP32_TO_FP16_SIMD(x) ck_fp32_to_fp16_simd(x)
#define CK_FP16_TO_FP32_SOFT(x) ck_fp16_to_fp32_soft(x)
#define CK_FP32_TO_FP16_SOFT(x) ck_fp32_to_fp16_soft(x)
 
/* Legacy compatibility (for files that used the old names) */
typedef ck_half ggml_half;
#define ggml_fp16_to_fp32 ck_fp16_to_fp32
#define ggml_fp32_to_fp16 ck_fp32_to_fp16
#define GGML_FP16_TO_FP32 CK_FP16_TO_FP32
#define GGML_FP32_TO_FP16 CK_FP32_TO_FP16
 
/* ============================================================================
 * SSE Optimized Kernels
 * ============================================================================ */
 
void gemm_nt_q5_0_sse_v2(const float *A, const void *B, const float *bias, float *C, int M, int N, int K);
void gemm_nt_q6_k_sse(const float *A, const void *B, const float *bias, float *C, int M, int N, int K);
void gemm_nt_q6_k_ref(const float *A, const void *B, const float *bias, float *C, int M, int N, int K);
void gemv_q4_k_q8_k_sse(float *y, const void *W, const void *x_q8, int M, int K);
void quantize_row_q8_k_sse(const float *x, void *vy, int k);
void rmsnorm_q8_k_fused(const float *input, const float *gamma, void *vy, int tokens, int d_model, int aligned_embed_dim, float eps);
 
/* Q5_K kernels (reference implementation) */
void gemv_q5_k_ref(float *y, const void *W, const float *x, int M, int K);
void gemm_nt_q5_k_ref(const float *A, const void *B, const float *bias, float *C, int M, int N, int K);
void gemv_q5_k(float *y, const void *W, const float *x, int M, int K);
void gemm_nt_q5_k(const float *A, const void *B, const float *bias, float *C, int M, int N, int K);
 
/* INT8 activation batch GEMM kernels (Q5_0 weights x Q8_0 activations) */
void gemm_nt_q5_0_q8_0(const void *A_q8, const void *B_q5, const float *bias, float *C, int M, int N, int K);
void gemm_nt_q5_0_q8_0_unroll_avx(const void *A_q8, const void *B_q5, const float *bias, float *C, int M, int N, int K);
void vec_dot_q5_0_q8_0(int n, float *s, const void *vx, const void *vy);
void vec_dot_q8_0_q8_0(int n, float *s, const void *vx, const void *vy);
void quantize_row_q8_0(const float *x, void *vy, int k);
 
#ifdef __cplusplus
}
#endif
 
#endif /* CKERNEL_QUANT_H */