fn vec_dot_unopt()

in candle-core/src/quantized/k_quants.rs [1585:1641]
52 lines of code
11 McCabe index (conditional complexity)

    fn vec_dot_unopt(n: usize, xs: &[Self], ys: &[Self::VecDotType]) -> Result<f32> {
        if n % QK_K != 0 {
            crate::bail!("vec_dot_q6k_q8k: {n} is not divisible by {QK_K}")
        }

        let mut aux8 = [0i8; QK_K];
        let mut aux16 = [0i16; 8];
        let mut sums = [0f32; 8];
        let mut aux32 = [0f32; 8];

        for (x, y) in xs.iter().zip(ys.iter()) {
            let q4 = &x.ql;
            let qh = &x.qh;
            let q8 = &y.qs;
            aux32.fill(0f32);

            for j in (0..QK_K).step_by(128) {
                let aux8 = &mut aux8[j..];
                let q4 = &q4[j / 2..];
                let qh = &qh[j / 4..];
                for l in 0..32 {
                    aux8[l] = (((q4[l] & 0xF) | ((qh[l] & 3) << 4)) as i32 - 32) as i8;
                    aux8[l + 32] =
                        (((q4[l + 32] & 0xF) | (((qh[l] >> 2) & 3) << 4)) as i32 - 32) as i8;
                    aux8[l + 64] = (((q4[l] >> 4) | (((qh[l] >> 4) & 3) << 4)) as i32 - 32) as i8;
                    aux8[l + 96] =
                        (((q4[l + 32] >> 4) | (((qh[l] >> 6) & 3) << 4)) as i32 - 32) as i8;
                }
            }

            for (j, &scale) in x.scales.iter().enumerate() {
                let scale = scale as f32;
                let q8 = &q8[16 * j..];
                let aux8 = &aux8[16 * j..];
                for l in 0..8 {
                    aux16[l] = q8[l] as i16 * aux8[l] as i16;
                }
                for l in 0..8 {
                    aux32[l] += scale * aux16[l] as f32
                }
                let q8 = &q8[8..];
                let aux8 = &aux8[8..];
                for l in 0..8 {
                    aux16[l] = q8[l] as i16 * aux8[l] as i16;
                }
                for l in 0..8 {
                    aux32[l] += scale * aux16[l] as f32
                }
            }

            let d = x.d.to_f32() * y.d;
            for (sum, &a) in sums.iter_mut().zip(aux32.iter()) {
                *sum += a * d;
            }
        }
        Ok(sums.iter().sum())
    }