k_quants: WIP super-blocks with 64 weights

Q2_K works on Metal and is very slightly faster
than QK_K = 256 (23.8 ms vs 24.2 ms).

ggml-metal.metal

@@ -863,6 +863,7 @@ static void dequantize_row_q2_k(device const block_q2_k * x, device float * y, i
 
         device const uint8_t * q = x[i].qs;
 
+#if QK_K == 256
         int is = 0;
         float dl, ml;
         for (int n = 0; n < QK_K; n += 128) {
@@ -881,6 +882,19 @@ static void dequantize_row_q2_k(device const block_q2_k * x, device float * y, i
             }
             q += 32;
         }
+#else
+        float dl1 = d * (x[i].scales[0] & 0xF), ml1 = min * (x[i].scales[0] >> 4);
+        float dl2 = d * (x[i].scales[1] & 0xF), ml2 = min * (x[i].scales[1] >> 4);
+        float dl3 = d * (x[i].scales[2] & 0xF), ml3 = min * (x[i].scales[2] >> 4);
+        float dl4 = d * (x[i].scales[3] & 0xF), ml4 = min * (x[i].scales[3] >> 4);
+        for (int l = 0; l < 16; ++l) {
+            y[l+ 0] = dl1 * ((q[l] >> 0) & 3) - ml1;
+            y[l+16] = dl2 * ((q[l] >> 2) & 3) - ml2;
+            y[l+32] = dl3 * ((q[l] >> 4) & 3) - ml3;
+            y[l+48] = dl4 * ((q[l] >> 6) & 3) - ml4;
+        }
+        y += QK_K;
+#endif
 
     }
 }
@@ -1153,6 +1167,9 @@ kernel void kernel_mul_mat_q2_k_f32(
     const int nth = tptg.x*tptg.y;
     const int ith = tptg.y*tpitg.x + tpitg.y;
 
+    float sumf = 0;
+
+#if QK_K == 256
     const int tid = tpitg.y;    // 0...16
     const int il  = tid/4;      // 0...3
     const int ir  = tid%4;      // 0...3
@@ -1165,9 +1182,6 @@ kernel void kernel_mul_mat_q2_k_f32(
     const int y_offset = 64*il + n*ir;
     const int q_offset = 32*ip + n*ir;
 
-    sum[ith] = 0.0f;
-
-    float sumf = 0;
     for (int i = tpitg.x; i < nb; i += tptg.x) {
 
         device const uint8_t * q = x[i].qs + q_offset;
@@ -1180,7 +1194,6 @@ kernel void kernel_mul_mat_q2_k_f32(
 
         device const float   * y = yy + i*QK_K + y_offset;
 
-        //float4 s = {0.f, 0.f, 0.f, 0.f};
         float2 s = {0.f, 0.f};
         float smin = 0;
         for (int l = 0; l < n; ++l) {
@@ -1195,25 +1208,38 @@ kernel void kernel_mul_mat_q2_k_f32(
         sumf += dall * (s[0] * d1 + s[1] * d2) - dmin * smin;
 
     }
+#else
+    const int il = 4 * tpitg.x;
+
+    uint32_t aux[2];
+    thread const uint8_t * d = (thread const uint8_t *)aux;
+    thread const uint8_t * m = (thread const uint8_t *)aux + 4;
+
+    for (int i = tpitg.y; i < nb; i += tptg.y) {
+
+        device const uint8_t * q = x[i].qs + il;
+        device const float   * y = yy + i*QK_K + il;
+
+        const float dall = (float)x[i].d;
+        const float dmin = (float)x[i].dmin;
+
+        device const uint32_t * a = (device const uint32_t *)x[i].scales;
+        aux[0] = a[0] & 0x0f0f0f0f;
+        aux[1] = (a[0] >> 4) & 0x0f0f0f0f;
+
+        for (int l = 0; l < 4; ++l) {
+            sumf += y[l+ 0] * (dall * d[0] * ((q[l] >> 0) & 3) - dmin * m[0])
+                  + y[l+16] * (dall * d[1] * ((q[l] >> 2) & 3) - dmin * m[1])
+                  + y[l+32] * (dall * d[2] * ((q[l] >> 4) & 3) - dmin * m[2])
+                  + y[l+48] * (dall * d[3] * ((q[l] >> 6) & 3) - dmin * m[3]);
+        }
+    }
+#endif
+
     sum[ith] = sumf;
 
-    //int mask1 = (ith%4 == 0);
-    //int mask2 = (ith%16 == 0);
-
-    //threadgroup_barrier(mem_flags::mem_threadgroup);
-    //for (int i = 1; i < 4; ++i) sum[ith] += mask1 * sum[ith + i];
-    //threadgroup_barrier(mem_flags::mem_threadgroup);
-    //for (int i = 4; i < 16; i += 4) sum[ith] += mask2 * sum[ith + i];
-    //threadgroup_barrier(mem_flags::mem_threadgroup);
-    //if (ith == 0) {
-    //    for (int i = 16; i < nth; i += 16) sum[0] += sum[i];
-    //    dst[r1*ne0 + r0] = sum[0];
-    //}
-
     //
     // Accumulate the sum from all threads in the threadgroup
-    // This version is slightly faster than the commented out one below,
-    // which I copy-pasted from ggerganov's q4_0 dot product for metal.
     //
     threadgroup_barrier(mem_flags::mem_threadgroup);
     if (ith%4 == 0) {