metal : small improvement for Q4_K

Author: Kawrakow

ggml-metal.metal

@@ -971,7 +971,7 @@ kernel void kernel_mul_mat_q4_k_f32(
 
     const uint16_t kmask1 = 0x3f3f;
     const uint16_t kmask2 = 0x0f0f;
-    const uint16_t kmask3 = 0x0303;
+    const uint16_t kmask3 = 0xc0c0;
 
     const int nb = ne00/QK_K;
 
@@ -991,16 +991,15 @@ kernel void kernel_mul_mat_q4_k_f32(
 
     const int im = il/2;  // 0 or 1. 0 computes 0,32 + 128,160, 1 computes 64,96 + 192,224
     const int in = il%2;
+    const int l0 = n*(2*ir + in);
 
     sum[ith] = 0.0f;
 
-    //uchar2 sc1, sc2;
-
     float sumf = 0;
     for (int i = tpitg.x; i < nb; i += tptg.x) {
 
-        device const uint8_t * q1 = (x + i)->qs + 32*im + n*(2*ir + in);
-        device const float   * y1 = yy + i*QK_K + 64*im + n*(2*ir + in);
+        device const uint8_t * q1 = (x + i)->qs + 32*im + l0;
+        device const float   * y1 = yy + i*QK_K + 64*im + l0;
         device const uint8_t * q2 = q1 + 64;
         device const float   * y2 = y1 + 128;
 
@@ -1011,21 +1010,16 @@ kernel void kernel_mul_mat_q4_k_f32(
 
         const uchar2 sc1 = as_type<uchar2>((uint16_t)(a[im+0] & kmask1));
         const uchar2 sc2 = as_type<uchar2>((uint16_t)(a[im+2] & kmask1));
-        const uchar2 sc3 = as_type<uchar2>((uint16_t)(((a[im+4] >> 0) & kmask2) | (((a[im+0] >> 6) & kmask3) << 4)));
-        const uchar2 sc4 = as_type<uchar2>((uint16_t)(((a[im+4] >> 4) & kmask2) | (((a[im+2] >> 6) & kmask3) << 4)));
+        const uchar2 sc3 = as_type<uchar2>((uint16_t)(((a[im+4] >> 0) & kmask2) | ((a[im+0] & kmask3) >> 2)));
+        const uchar2 sc4 = as_type<uchar2>((uint16_t)(((a[im+4] >> 4) & kmask2) | ((a[im+2] & kmask3) >> 2)));
 
-        float4 s1 = {0.f, 0.f, 0.f, 0.f};
-        float4 s2 = {0.f, 0.f, 0.f, 0.f};
+        float2 s = {0.f, 0.f};
         for (int l = 0; l < n; ++l) {
-            s1[0] += y1[l+ 0] * (q1[l] & 0xF); s1[1] += y1[l+ 0];
-            s1[2] += y1[l+32] * (q1[l] >>  4); s1[3] += y1[l+32];
-            s2[0] += y2[l+ 0] * (q2[l] & 0xF); s2[1] += y2[l+ 0];
-            s2[2] += y2[l+32] * (q2[l] >>  4); s2[3] += y2[l+32];
+            s[0] += y1[l] * sc1[0] * (q1[l] & 0xF) + y1[l+32] * sc1[1] * (q1[l] >> 4)
+                  + y2[l] * sc3[0] * (q2[l] & 0xF) + y2[l+32] * sc3[1] * (q2[l] >> 4);
+            s[1] += y1[l] * sc2[0] + y1[l+32] * sc2[1] + y2[l] * sc4[0] + y2[l+32] * sc4[1];
         }
-        sumf += dall * (s1[0] * sc1[0] + s1[2] * sc1[1]
-                     +  s2[0] * sc3[0] + s2[2] * sc3[1])
-              - dmin * (s1[1] * sc2[0] + s1[3] * sc2[1]
-                     +  s2[1] * sc4[0] + s2[3] * sc4[1]);
+        sumf += dall * s[0] - dmin * s[1];
 
     }
     sum[ith] = sumf;