1 use std::mem::size_of; 2 3 use once_cell::sync::OnceCell; 4 5 const N_THREADS: usize = 32; 6 const N_ROUNDS: usize = 100_000_000; 7 8 static CELL: OnceCell<usize> = OnceCell::new(); 9 main()10fn main() { 11 let start = std::time::Instant::now(); 12 let threads = 13 (0..N_THREADS).map(|i| std::thread::spawn(move || thread_main(i))).collect::<Vec<_>>(); 14 for thread in threads { 15 thread.join().unwrap(); 16 } 17 println!("{:?}", start.elapsed()); 18 println!("size_of::<OnceCell<()>>() = {:?}", size_of::<OnceCell<()>>()); 19 println!("size_of::<OnceCell<bool>>() = {:?}", size_of::<OnceCell<bool>>()); 20 println!("size_of::<OnceCell<u32>>() = {:?}", size_of::<OnceCell<u32>>()); 21 } 22 thread_main(i: usize)23fn thread_main(i: usize) { 24 for _ in 0..N_ROUNDS { 25 let &value = CELL.get_or_init(|| i); 26 assert!(value < N_THREADS) 27 } 28 } 29