Q4_1 quantization (#193)

* Add AVX2 version of ggml_vec_dot_q4_1

* Small optimisations to q4_1 dot product (@Const-me)

* Rearrange Q4_1 quantization to work for multipart models. (Fix #152)

* Fix ggml_vec_mad_q4_1 too

* Fix non-vectorised q4_1 vec mul

ggml.c

@@ -607,10 +607,11 @@ void quantize_row_q4_1(const float * restrict x, void * restrict y, int k) {
     assert(k % QK == 0);
 
     const int nb = k / QK;
+    const size_t bs = 2*sizeof(float) + QK/2;
 
-    float   * restrict pm = (float *)   (y);
-    float   * restrict pd = (float *)   (pm + nb);
-    uint8_t * restrict pb = (uint8_t *) (pd + nb);
+    uint8_t * restrict pd = ((uint8_t *)y + 0*bs);
+    uint8_t * restrict pm = ((uint8_t *)y + 0*bs +   sizeof(float));
+    uint8_t * restrict pb = ((uint8_t *)y + 0*bs + 2*sizeof(float));
 
     uint8_t pp[QK/2];
 
@@ -627,8 +628,10 @@ void quantize_row_q4_1(const float * restrict x, void * restrict y, int k) {
         const float d = (max - min) / ((1 << 4) - 1);
         const float id = d ? 1.0f/d : 0.0f;
 
-        pm[i] = min;
-        pd[i] = d;
+        *(float *)pm = min;
+        *(float *)pd = d;
+        pm += bs;
+        pd += bs;
 
         for (int l = 0; l < QK; l += 2) {
             const float v0 = (x[i*QK + l + 0] - min)*id;
@@ -643,7 +646,8 @@ void quantize_row_q4_1(const float * restrict x, void * restrict y, int k) {
             pp[l/2] = vi0 | (vi1 << 4);
         }
 
-        memcpy(pb + i*QK/2, pp, sizeof(pp));
+        memcpy(pb, pp, sizeof(pp));
+        pb += bs;
     }
 }
 
@@ -687,16 +691,17 @@ void dequantize_row_q4_1(const void * restrict x, float * restrict y, int k) {
     assert(k % QK == 0);
 
     const int nb = k / QK;
+    const size_t bs = 2*sizeof(float) + QK/2;
 
-    const float   * restrict pm = (const float *)   (x);
-    const float   * restrict pd = (const float *)   (pm + nb);
-    const uint8_t * restrict pb = (const uint8_t *) (pd + nb);
+    const uint8_t * restrict pd = ((const uint8_t *)x + 0*bs);
+    const uint8_t * restrict pm = ((const uint8_t *)x + 0*bs + sizeof(float));
+    const uint8_t * restrict pb = ((const uint8_t *)x + 0*bs + 2*sizeof(float));
 
     for (int i = 0; i < nb; i++) {
-        const float m = pm[i];
-        const float d = pd[i];
+        const float d = *(const float *) (pd + i*bs);
+        const float m = *(const float *) (pm + i*bs);
 
-        const uint8_t * restrict pp = pb + i*QK/2;
+        const uint8_t * restrict pp = pb + i*bs;
 
         for (int l = 0; l < QK; l += 2) {
             const uint8_t vi = pp[l/2];
@@ -1584,28 +1589,109 @@ inline static void ggml_vec_dot_q4_0(const int n, float * restrict s, const void
 inline static void ggml_vec_dot_q4_1(const int n, float * restrict s, const void * restrict x, const void * restrict y) {
     const int nb = n / QK;
 
-    const float * restrict pm0 = (const float *) x;
-    const float * restrict pm1 = (const float *) y;
+    const size_t bs = 2*sizeof(float) + QK/2;
 
-    const float * restrict pd0 = (const float *) (pm0 + nb);
-    const float * restrict pd1 = (const float *) (pm1 + nb);
+    const uint8_t * restrict pd0 = ((const uint8_t *)x + 0*bs);
+    const uint8_t * restrict pd1 = ((const uint8_t *)y + 0*bs);
+
+    const uint8_t * restrict pm0 = ((const uint8_t *)x + 0*bs + sizeof(float));
+    const uint8_t * restrict pm1 = ((const uint8_t *)y + 0*bs + sizeof(float));
 
-    const uint8_t * restrict pb0 = (const uint8_t *) (pd0 + nb);
-    const uint8_t * restrict pb1 = (const uint8_t *) (pd1 + nb);
+    const uint8_t * restrict pb0 = ((const uint8_t *)x + 0*bs + 2*sizeof(float));
+    const uint8_t * restrict pb1 = ((const uint8_t *)y + 0*bs + 2*sizeof(float));
 
     float sumf = 0.0;
 
-#if 1
+#if defined(__AVX2__)
+#if QK == 32
+    // Initialize accumulator with zeros
+    __m256 acc = _mm256_setzero_ps();
+    // Accumulator for constant offsets
+    float acc_offset = 0.0f;
+
+    // Main loop
+    for (int i = 0; i < nb; ++i) {
+        const float * m0 = (const float *) (pm0 + i*bs);
+        const float * m1 = (const float *) (pm1 + i*bs);
+
+        const float * d0 = (const float *) (pd0 + i*bs);
+        const float * d1 = (const float *) (pd1 + i*bs);
+
+        const uint8_t * restrict p0 = pb0 + i*bs;
+        const uint8_t * restrict p1 = pb1 + i*bs;
+
+        const __m256 d0v = _mm256_broadcast_ss( d0 );
+        const __m256 d1v = _mm256_broadcast_ss( d1 );
+        const __m256 m0v = _mm256_broadcast_ss( m0 );
+        const __m256 m1v = _mm256_broadcast_ss( m1 );
+
+
+        // Compute combined scale for the block
+        const __m256 scale_01 = _mm256_mul_ps( d0v, d1v );
+
+        // Compute cross scales for the block
+        const __m256 scale_0 = _mm256_mul_ps( d0v, m1v );
+        const __m256 scale_1 = _mm256_mul_ps( m0v, d1v );
+        const __m256 cross_scales = _mm256_blend_ps( scale_0, scale_1, 0b10101010 );
+
+        // Load 16 bytes, and unpack 4 bit fields into bytes, making 32 bytes
+        __m256i bx = bytesFromNibbles( p0 );
+        __m256i by = bytesFromNibbles( p1 );
+
+        // Now we have a vector with bytes in [ 0 .. 15 ] interval.
+
+        // Sign-extend first 16 signed bytes into int16_t
+        __m256i x16 = _mm256_cvtepi8_epi16( _mm256_castsi256_si128( bx ) );
+        __m256i y16 = _mm256_cvtepi8_epi16( _mm256_castsi256_si128( by ) );
+        // Compute products of int16_t integers, add pairwise
+        __m256i i32 = _mm256_madd_epi16( x16, y16 );
+
+        // Sign-extend last 16 signed bytes into int16_t vectors
+        __m256i x16_h = _mm256_cvtepi8_epi16( _mm256_extracti128_si256( bx, 1 ) );
+        __m256i y16_h = _mm256_cvtepi8_epi16( _mm256_extracti128_si256( by, 1 ) );
+        // Accumulate products of int16_t integers
+        i32 = _mm256_add_epi32( i32, _mm256_madd_epi16( x16_h, y16_h ) );
+
+        // compute sums of unsigned bytes in bx, by in blocks of 8.
+        // This results in a layout like X100 0000 X200 0000 X300 0000 X400 0000,
+        // which we then interleave as X100 Y100 X200 Y200 X300 Y300 X400 Y400.
+        // so if we then cast to 8 singles, we get 8 floats like [ x0_7, y0_7, x8_15, y8_15, x16_23, y16_23, x24_31, y24_31 ]
+        __m256i xsumi = _mm256_sad_epu8( bx, _mm256_setzero_si256() );
+        __m256i ysumi = _mm256_sad_epu8( by, _mm256_setzero_si256() );
+        __m256i sumsi = _mm256_or_si256( xsumi, _mm256_slli_si256( ysumi, 4 ) );
+        __m256  sums  = _mm256_cvtepi32_ps( sumsi );
+
+        // Convert int32_t to float
+        __m256 p = _mm256_cvtepi32_ps( i32 );
+        // Apply the scale, and accumulate
+        // acc += d0*d1*x*y + d0*m1*x + d1*m0*y
+        acc = _mm256_fmadd_ps( scale_01, p, acc );
+        acc = _mm256_fmadd_ps( cross_scales, sums, acc );
+        // acc_offset += m0*m1 (for each entry in the block)
+        acc_offset += (*m0)*(*m1);
+    }
+
+    // Return horizontal sum of the acc vector
+    __m128 res = _mm256_extractf128_ps( acc, 1 );
+    res = _mm_add_ps( res, _mm256_castps256_ps128( acc ) );
+    res = _mm_add_ps( res, _mm_movehl_ps( res, res ) );
+    res = _mm_add_ss( res, _mm_movehdup_ps( res ) );
+
+    sumf = _mm_cvtss_f32( res ) + acc_offset * QK;
+#else
+#error "not implemented for QK"
+#endif
+#else
     // scalar
     for (int i = 0; i < nb; i++) {
-        const float m0 = pm0[i];
-        const float m1 = pm1[i];
+        const float m0 = *(const float *) (pm0 + i*bs);
+        const float m1 = *(const float *) (pm1 + i*bs);
 
-        const float d0 = pd0[i];
-        const float d1 = pd1[i];
+        const float d0 = *(const float *) (pd0 + i*bs);
+        const float d1 = *(const float *) (pd1 + i*bs);
 
-        const uint8_t * restrict p0 = pb0 + i*QK/2;
-        const uint8_t * restrict p1 = pb1 + i*QK/2;
+        const uint8_t * restrict p0 = pb0 + i*bs;
+        const uint8_t * restrict p1 = pb1 + i*bs;
 
         for (int j = 0; j < QK/2; j++) {
             const uint8_t v0 = p0[j];
@@ -1839,16 +1925,17 @@ inline static void ggml_vec_mad_q4_1(const int n, float * restrict y, void * res
     assert(n % QK == 0);
 
     const int nb = n / QK;
+    const size_t bs = 2*sizeof(float) + QK/2;
 
-    const float   * restrict pm = (const float *)   (x);
-    const float   * restrict pd = (const float *)   (pm + nb);
-    const uint8_t * restrict pb = (const uint8_t *) (pd + nb);
+    const uint8_t * restrict pd = ((const uint8_t *)x + 0*bs);
+    const uint8_t * restrict pm = ((const uint8_t *)x + 0*bs +   sizeof(float)); 
+    const uint8_t * restrict pb = ((const uint8_t *)x + 0*bs + 2*sizeof(float));
 
     for (int i = 0; i < nb; i++) {
-        const float m = pm[i];
-        const float d = pd[i];
+        const float d = *(const float *) (pd + i*bs);
+        const float m = *(const float *) (pm + i*bs);
 
-        const uint8_t * restrict pp = pb + i*QK/2;
+        const uint8_t * restrict pp = pb + i*bs;
 
         for (int l = 0; l < QK; l += 2) {
             const uint8_t vi = pp[l/2];

utils.cpp

@@ -489,7 +489,8 @@ size_t ggml_quantize_q4_0(float * src, void * dst, int n, int k, int qk, int64_t
 
 size_t ggml_quantize_q4_1(float * src, void * dst, int n, int k, int qk, int64_t * hist) {
     const int nb = k / qk;
-    const size_t row_size = nb*(2*sizeof(float) + sizeof(uint8_t)*qk/2);
+    const size_t bs = (2*sizeof(float) + sizeof(uint8_t)*qk/2);
+    const size_t row_size = nb*bs;
 
     assert(k % qk == 0);
 
@@ -498,10 +499,10 @@ size_t ggml_quantize_q4_1(float * src, void * dst, int n, int k, int qk, int64_t
 
     char * pdst = (char *) dst;
 
-    for (int j = 0; j < n; j += k) {
-        float   * pm = (float *)   (pdst + (j/k)*row_size);
-        float   * pd = (float *)   (pm + nb);
-        uint8_t * pb = (uint8_t *) (pd + nb);
+    for (int j = 0; j < n; j += k) { 
+        uint8_t * pd = (uint8_t *) (pdst + (j/k)*row_size + 0*bs);
+        uint8_t * pm = (uint8_t *) (pdst + (j/k)*row_size + 0*bs +   sizeof(float));
+        uint8_t * pb = (uint8_t *) (pdst + (j/k)*row_size + 0*bs + 2*sizeof(float));
 
         //printf("n = %d, k = %d, nb = %d, row_size = %d, j = %d, pm = %p, pd = %p, pb = %p\n", n, k, nb, row_size, j, pm, pd, pb);
 
@@ -519,8 +520,10 @@ size_t ggml_quantize_q4_1(float * src, void * dst, int n, int k, int qk, int64_t
                 const float d = (max - min) / ((1 << 4) - 1);
                 const float id = d ? 1.0f/d : 0.0f;
 
-                pm[i] = min;
-                pd[i] = d;
+                *(float *) pd = d;
+                *(float *) pm = min;
+                pd += bs; 
+                pm += bs;
 
                 for (int l = 0; l < qk; l += 2) {
                     const float v0 = (src[j + i*qk + l + 0] - min)*id;
@@ -538,7 +541,8 @@ size_t ggml_quantize_q4_1(float * src, void * dst, int n, int k, int qk, int64_t
                     pp[l/2] = vi0 | (vi1 << 4);
                 }
 
-                memcpy(pb + i*qk/2, pp, pp_size);
+                memcpy(pb, pp, pp_size);
+                pb += bs;
             }
         }
     }