bevy/examples/app/thread_pool_resources.rs

use bevy::prelude::*;
use bevy_app::DefaultTaskPoolOptions;

/// This example illustrates how to customize the thread pool used internally (e.g. to only use a
/// certain number of threads).
fn main() {
    App::build()
        .add_resource(DefaultTaskPoolOptions::with_num_threads(4))
        .add_default_plugins()
        .run();
}