fn main() -> std::io::Result<()> {
    use perf_event::{Builder, Group};
    use perf_event::events::Hardware;

    let mut group = Group::new()?;
    let cycles = Builder::new().group(&mut group).kind(Hardware::CPU_CYCLES).build()?;
    let insns = Builder::new().group(&mut group).kind(Hardware::INSTRUCTIONS).build()?;

    let vec = (0..=51).collect::<Vec<_>>();

    group.enable()?;
    println!("{:?}", vec);
    group.disable()?;

    let counts = group.read()?;
    println!("cycles / instructions: {} / {} ({:.2} cpi)",
             counts[&cycles],
             counts[&insns],
             (counts[&cycles] as f64 / counts[&insns] as f64));

    Ok(())
}