ggml : fix quantize_row_q4_1() ARM_NEON (close #876)

ggml.c

@@ -599,10 +599,7 @@ static void quantize_row_q4_0(const float * restrict x, void * restrict vy, int
         for (int l = 0; l < 2; l++) amaxv[4*l] = vmaxq_f32(amaxv[4*l], amaxv[4*l+2]);
         for (int l = 0; l < 1; l++) amaxv[8*l] = vmaxq_f32(amaxv[8*l], amaxv[8*l+4]);
 
-        // absolute max
-        const float amax = MAX(
-                MAX(vgetq_lane_f32(amaxv[0], 0), vgetq_lane_f32(amaxv[0], 1)),
-                MAX(vgetq_lane_f32(amaxv[0], 2), vgetq_lane_f32(amaxv[0], 3)));
+        const float amax = vmaxvq_f32(amaxv[0]);
 
         const float d = amax / ((1 << 3) - 1);
         const float id = d ? 1.0f/d : 0.0f;
@@ -924,7 +921,7 @@ static void quantize_row_q4_1(const float * restrict x, void * restrict vy, int
         float32x4_t minv[8];
         float32x4_t maxv[8];
 
-        for (int l = 0; l < 8; l++) srcv[l] = vld1q_f32(x + i*32 + 4*l);
+        for (int l = 0; l < 8; l++) srcv[l] = vld1q_f32(x + i*QK + 4*l);
 
         for (int l = 0; l < 4; l++) minv[2*l] = vminq_f32(srcv[2*l], srcv[2*l + 1]);
         for (int l = 0; l < 2; l++) minv[4*l] = vminq_f32(minv[4*l], minv[4*l + 2]);
@@ -947,7 +944,8 @@ static void quantize_row_q4_1(const float * restrict x, void * restrict vy, int
 
         for (int l = 0; l < 8; l++) {
             const float32x4_t v  = vmulq_n_f32(vsubq_f32(srcv[l], minv0), id);
-            const int32x4_t   vi = vcvtq_s32_f32(v);
+            const float32x4_t vf = vaddq_f32(v, vdupq_n_f32(0.5f)); // needed to round to nearest
+            const int32x4_t   vi = vcvtq_s32_f32(vf);
 
             y[i].qs[2*l + 0] = vgetq_lane_s32(vi, 0) | (vgetq_lane_s32(vi, 1) << 4);
             y[i].qs[2*l + 1] = vgetq_lane_s32(vi, 2) | (vgetq_lane_s32(vi, 3) << 4);