AVX version for the q8-0 multiplications. (#598)

candle-core/src/quantized/avx.rs

@@ -56,7 +56,6 @@ pub(crate) fn vec_dot_q4_0_q8_0(n: usize, xs: &[BlockQ4_0], ys: &[BlockQ8_0]) ->
     }
 
     unsafe {
-        // Generic implementation.
         let mut acc = _mm256_setzero_ps();
         for (x, y) in xs.iter().zip(ys.iter()) {
             let d = _mm256_set1_ps(f16::to_f32(x.d) * f16::to_f32(y.d));
@@ -71,6 +70,25 @@ pub(crate) fn vec_dot_q4_0_q8_0(n: usize, xs: &[BlockQ4_0], ys: &[BlockQ8_0]) ->
     }
 }
 
+#[inline(always)]
+pub(crate) fn vec_dot_q8_0_q8_0(n: usize, xs: &[BlockQ8_0], ys: &[BlockQ8_0]) -> Result<f32> {
+    let qk = QK8_0;
+    if n % QK8_0 != 0 {
+        crate::bail!("vec_dot_q8_0_q8_0: {n} is not divisible by {qk}")
+    }
+    unsafe {
+        let mut acc = _mm256_setzero_ps();
+        for (x, y) in xs.iter().zip(ys.iter()) {
+            let d = _mm256_set1_ps(f16::to_f32(x.d) * f16::to_f32(y.d));
+            let bx = _mm256_loadu_si256(x.qs.as_ptr() as *const __m256i);
+            let by = _mm256_loadu_si256(y.qs.as_ptr() as *const __m256i);
+            let q = mul_sum_i8_pairs_float(bx, by);
+            acc = _mm256_fmadd_ps(d, q, acc);
+        }
+        Ok(hsum_float_8(acc))
+    }
+}
+
 const K_SHUFFLE: [u8; 128] = [
     0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
     4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7,

candle-core/src/quantized/k_quants.rs

@@ -421,7 +421,11 @@ impl GgmlType for BlockQ8_0 {
         Ok(())
     }
 
+    #[allow(unreachable_code)]
     fn vec_dot(n: usize, xs: &[Self], ys: &[Self::VecDotType]) -> Result<f32> {
+        #[cfg(target_feature = "avx")]
+        return super::avx::vec_dot_q8_0_q8_0(n, xs, ys);
+
         let qk = QK8_0;
         if n % QK8_0 != 0 {
             crate::bail!("vec_dot_q8_0_q8_0: {n} is not divisible by {qk}")