Get the number of logical / physical cores in Rust

sample_num_cpus.rs

// ref: https://docs.rs/num_cpus/latest/num_cpus/fn.get.html
fn main() {
    let logical_cpus = num_cpus::get();
    let physical_cpus = num_cpus::get_physical();

    println!("Logical CPUs: {}", logical_cpus);
    println!("Physical CPUs: {}", physical_cpus);

    /*
    if logical_cpus > physical_cpus {
        println!(
            "We have simultaneous multithreading with about {:.2} \
              logical cores to 1 physical core.",
            (logical_cpus as f64) / (physical_cpus as f64)
        );
    } else if logical_cpus == physical_cpus {
        println!(
            "Either we don't have simultaneous multithreading, or our \
              system doesn't support getting the number of physical CPUs."
        );
    } else {
        println!(
            "We have less logical CPUs than physical CPUs, maybe we only have access to \
              some of the CPUs on our system."
        );
    }
    */

    match logical_cpus.cmp(&physical_cpus) {
        std::cmp::Ordering::Greater => {
            println!(
                "We have simultaneous multithreading with about {:.2} \
                  logical cores to 1 physical core.",
                (logical_cpus as f64) / (physical_cpus as f64)
            );
        }
        std::cmp::Ordering::Equal => {
            println!(
                "Either we don't have simultaneous multithreading, or our \
                  system doesn't support getting the number of physical CPUs."
            );
        }
        std::cmp::Ordering::Less => {
            println!(
                "We have less logical CPUs than physical CPUs, maybe we only have access to \
                  some of the CPUs on our system."
            );
        }
    }
}