Function qsa_score_rows_tc 

pub fn qsa_score_rows_tc(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    q: DevicePtr,
    block_keys: DevicePtr,
    scores: DevicePtr,
    rows: u32,
    n_blocks_max: u32,
    first_pos: u32,
    score_stride: u32,
    ratio: u32,
    stream: u64,
) -> Result<()>

Tensor-core qsa_score_rows (split-q). Geometry differs from the per-(row,block) kernel: one CTA covers 16 rows x 64 blocks with 8 warps, so the launch count drops from rows*blocks to ~1/1000th of that.

Measured 39.010 → 1.831 ms average per call under nsys on a 28K prefill (qwen4_exp, GB10): ~21x. Selection-equivalent, not bit-exact — split-q carries ~17 mantissa bits, and the consumer is a top-k.