Function run 

pub fn run(
    b: &Bringup,
    checkpoint: &Path,
    ctx: usize,
    out: &Path,
    prompt: &[u32],
    reference: Reference,
) -> Runs

Run the model b brought up on every backend that brought it up, prompt first, for as many tokens as reference holds, in the order the backends were asked for: run_sequences of the one sequence.