Function qwen4_exp_check_rows 

pub(super) fn qwen4_exp_check_rows(
    m: &CpuModel<'_>,
    st: &mut State,
    gpu: &Gpu<'_>,
    rows: &[u32],
    next: Option<&[u32]>,
    pos0: usize,
    label: &str,
    prefill: bool,
) -> Result<()>

Compare the GPU’s rows against the CPU reference, which forwards the same tokens one at a time. With next (the token after each row), the CPU also runs the MTP head per row and the last row’s draft logits are compared with the GPU’s.