一、问题：mpsc如何发送各类不同的函数？
3个关键词：闭包、Box与FnOnce；请细品。
use std::sync::{mpsc,Arc,Mutex};
use std::thread;
fn process<F>(old:f32,name:String,f:F) where F: FnOnce(f32,String) {f(old,name);
}
fn add_f32(a:f32,b:f32) ->f32{a+b
}
fn doit(amount: f32,code:String){println!("amount:{:?} code:{:?}",amount,code);
}
fn workit(amount:f32){println!("amount:{:?}",amount);
}
fn test(){process(2.0, "b".into(), doit);let fn1: Box<dyn FnOnce()> = Box::new(move || doit(2.0,"hello cat!".into()));fn1();let fn2: Box<dyn FnOnce(f32,String)> = Box::new(move |amount:f32,code:String| doit(amount,code));fn2(2.0,"hello john!".into());let fn3:Box<dyn FnOnce(f32,String)> = Box::new(move |amount:f32,code:String| process(amount,code,doit));fn3(2.0,"hello rose!".into());let fn4: Box<dyn FnOnce()> = Box::new(move ||workit(3.0));fn4();let fn5: Box<dyn FnOnce()> = Box::new(move ||println!("hello world!"));fn5();// 带类型返还的结构let fn6:Box<dyn FnOnce()->f32> = Box::new(move ||add_f32(1.0,2.0));fn6();
}
// 定义闭包中没有参数输入的函数类型，做为发送对象
type box_fn = Box<dyn FnOnce() + Send>;
fn main(){//test();let (sender, receiver) = mpsc::channel::<box_fn>();let receiver = Arc::new(Mutex::new(receiver));// 注意：||中均没有参数，故是FnOnce(); 具体参考test()let vec_fn:Vec<Box<dyn FnOnce()+Send>> = vec![Box::new(move ||println!("hello world!")),Box::new(move ||workit(3.0)),Box::new(move || doit(2.0,"hello cat!".into()))];for f in vec_fn {sender.send(f).unwrap();}let rx = receiver.clone();let handle = thread::spawn(move ||{loop{let box_fn = rx.lock().unwrap().recv().unwrap() ;println!("from son thread!");box_fn();}});println!("main thread sended all box_fn!");handle.join().unwrap();}
二、线程池的应用：发送函数有什么用处？
如果需要让每一个函数都分配一个线程来执行这些函数（任务），或者用一个线程池来执行函数，这个时侯就可以用上场了。
在线程池中，FnOnce是一个其中的灵魂。他可以把所有的函数进行抽象统一，便一管理和执行。
说明：如果你想写一个更专业的，可以参考 github rust-threadpool库：
https://github.com/rust-threadpool/rust-threadpool/blob/master/src/lib.rs
// 这个线程池是一个比较粗的框架；可以执行不同策略类型：多周期、趋势、套利、市场中性等各类策略组的运行。
use std::sync::atomic::AtomicU32;
use std::sync::{mpsc, Arc, Mutex};
use std::thread;
use std::time::Duration;
// 存在不均衡的情况 => steal work todo!
// 简易的threadpool，没有用condvar.
// send_num可以不要，这里只是记录一下发送的情况
pub struct ThreadPool {threads_num: usize,workers: Vec<Worker>,sender: mpsc::Sender<Message>,send_num: Arc<Mutex<usize>>,
}
// 定义执行各类函数的参数结构类型，带不带参数，带参数的类型，多少
// 其中参数只是举例。比如某类策略只需要输入vec<bar>或vec<tick>; 某类策略需要输入hashmap<string,vec<bar>>;
// 或者套利策略中：两组或多组pair: (vec<bar>,vec<bar>)......
// 一组1min vec<bar>,3min vec<bar>,5min vec<bar>等......
// 不同的策略类型，都可以在这里进行抽象；
// 最后线程池可以执行各类不同的策略；
enum StrategyFn
{T(Box<dyn FnOnce() + Send +'static>),U(Box<dyn FnOnce(f32, f32) + Send +'static>,Arc<f32>,Arc<f32>),W(Box<dyn FnOnce(Vec<f32>, f32) + Send +'static>,Arc<Vec<f32>>,Arc<f32>),
}// 定义发送内容
enum Message{Task(Task),Shutdown,
}
struct Task{job :Job,task_id :usize,
}type Job = Box<dyn FnOnce() + Send +'static>;impl ThreadPool {pub fn new(threads_num: usize) -> ThreadPool {assert!(threads_num > 0);let (sender, receiver) = mpsc::channel::<Message>();let receiver = Arc::new(Mutex::new(receiver));let mut workers = Vec::with_capacity(threads_num);let send_num = Arc::new(Mutex::new(0_usize));let execute_num = Arc::new(Mutex::new(0_usize));for id in 0..threads_num {let mut worker = Worker::new(id);worker.run(&receiver, &execute_num);workers.push(worker);}ThreadPool { threads_num,workers, sender,send_num}}pub fn execute(&mut self, task_id:usize,strategy_fn: StrategyFn){let mut job:Box<dyn FnOnce()+Send +'static> = Box::new(move||{});match strategy_fn{StrategyFn::U(f, input1, input2) => {job = Box::new(move || f(input1.as_ref().clone(),input2.as_ref().clone()));},StrategyFn::T(f) =>{job = Box::new(move || f());}StrategyFn::W(f,input1,input2)=> {job = Box::new(move || f(input1.as_ref().clone(),input2.as_ref().clone()));},}let task = Task{job:job,task_id:task_id};let mut send_num = self.send_num.lock().unwrap();*send_num = *send_num +1;self.sender.send(Message::Task(task)).unwrap();}}pub struct Worker {id: usize,thread: Option<thread::JoinHandle<()>>,}impl Worker {pub fn new(id: usize)-> Self{Worker {id:id,thread: None,}}pub fn run(&mut self, receiver: &Arc<Mutex<mpsc::Receiver<Message>>>,execute_num: &Arc<Mutex<usize>>){let id = self.id;let receiver = receiver.clone();let execute_num = execute_num.clone();let thread = thread::spawn(move || loop {let msg = receiver.lock().unwrap().recv().unwrap();match msg{Message::Task(task) => {println!("Worker {} got a task; executing task {}.", id,task.task_id);let mut execute_num = execute_num.lock().unwrap();*execute_num = *execute_num + 1;println!("work {} = >execute_num: {}", id,*execute_num);(task.job)();},Message::Shutdown => {println!("Worker {} received shutdown message.", id);break;//很关键}}});self.thread = Some(thread);}
}impl Drop for ThreadPool {fn drop(&mut self) {for _ in 0..self.threads_num{self.sender.send(Message::Shutdown).unwrap();}println!("drop worker :{:?}",self.workers.len());for (i,worker) in (&mut self.workers).into_iter().enumerate() {println!("------Shutting down worker {} i:{} -----------", worker.id,i);if let Some(thread) = worker.thread.take() {thread.join().unwrap();}}}
}
// 这里只是通过宏生成一类：U(Box<dyn FnOnce(f32, f32) + Send +'static>,Arc<f32>,Arc<f32>)策略数据类型；
//
macro_rules! create_strategy_U{($($s:ident),*) => ($(pub fn $s(_a:f32,_b:f32){println!("run 【U】 strategy {:?}",stringify!($s));//thread::sleep(Duration::from_millis(1));})* );
}
//这里只是通过宏生成一类：T(Box<dyn FnOnce() + Send +'static>)策略数据类型；
macro_rules! create_strategy_T{($($s:ident),*) => ($(pub fn $s(){println!("run 【T】 strategy {:?}",stringify!($s));//thread::sleep(Duration::from_millis(1));})* );
}
// 生成U策略组若干
create_strategy_U!(A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q);
// 生成T策略组若干
create_strategy_T!(AA,BB,CC,DD,EE,FF,GG);
pub fn main() {let mut pool = ThreadPool::new(2);let input1 = Arc::new(1.0);let input2 = Arc::new(2.0);let u_strategies = vec![A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q];let t_strategies = vec![AA,BB,CC,DD,EE,FF,GG];println!("u_strategies num : {:?}",u_strategies.len());for (task_id,u_strategy) in u_strategies.into_iter().enumerate(){let strategy_fn = StrategyFn::U(Box::new(u_strategy),input1.clone(), input2.clone());pool.execute(task_id as usize,strategy_fn);}println!("t_strategies num : {:?}",t_strategies.len());for (task_id,t_strategy) in t_strategies.into_iter().enumerate(){let strategy_fn = StrategyFn::T(Box::new(t_strategy));pool.execute(task_id as usize,strategy_fn);}println!("toal send_num : {:?}",*pool.send_num.lock().unwrap());
}输出：
能过U和T类型策略运行实例，说明只要事先进行枚举定义，可以看出，这个线程池可以执行不同类型的策略。
这里有一个问题：这些线程池中线程中如何抢到这个任务，并完整执行完这些任务？这里依靠的是Arc<Mutex<mpsc::Receiver>>结构来保证。
具体如下：
u_strategies num : 17
t_strategies num : 7
toal send_num : 24
drop worker :4
------Shutting down worker 0 i:0 -----------
Worker 2 got a task; executing task 3.
work 2 = >execute_num: 1
run 【U】 strategy "D"
Worker 2 got a task; executing task 4.
work 2 = >execute_num: 2
run 【U】 strategy "E"
Worker 2 got a task; executing task 5.
work 2 = >execute_num: 3
Worker 1 got a task; executing task 1.
Worker 3 got a task; executing task 2.
Worker 0 got a task; executing task 0.
run 【U】 strategy "F"
Worker 2 got a task; executing task 6.
work 1 = >execute_num: 4
run 【U】 strategy "B"
Worker 1 got a task; executing task 7.
work 3 = >execute_num: 5
run 【U】 strategy "C"
work 0 = >execute_num: 6
run 【U】 strategy "A"
Worker 0 got a task; executing task 9.
Worker 3 got a task; executing task 8.
work 2 = >execute_num: 7
run 【U】 strategy "G"
Worker 2 got a task; executing task 10.
work 1 = >execute_num: 8
run 【U】 strategy "H"
Worker 1 got a task; executing task 11.
work 0 = >execute_num: 9
run 【U】 strategy "J"
Worker 0 got a task; executing task 12.
work 3 = >execute_num: 10
run 【U】 strategy "I"
Worker 3 got a task; executing task 13.
work 2 = >execute_num: 11
run 【U】 strategy "K"
Worker 2 got a task; executing task 14.
work 1 = >execute_num: 12
run 【U】 strategy "L"
Worker 1 got a task; executing task 15.
work 0 = >execute_num: 13
run 【U】 strategy "M"
Worker 0 got a task; executing task 16.
work 3 = >execute_num: 14
run 【U】 strategy "N"
Worker 3 got a task; executing task 0.
work 2 = >execute_num: 15
run 【U】 strategy "O"
Worker 2 got a task; executing task 1.
work 1 = >execute_num: 16
run 【U】 strategy "P"
Worker 1 got a task; executing task 2.
work 0 = >execute_num: 17
run 【U】 strategy "Q"
Worker 0 got a task; executing task 3.
work 3 = >execute_num: 18
run 【T】 strategy "AA"
Worker 3 got a task; executing task 4.
work 2 = >execute_num: 19
run 【T】 strategy "BB"
Worker 2 got a task; executing task 5.
work 1 = >execute_num: 20
run 【T】 strategy "CC"
Worker 1 got a task; executing task 6.
work 0 = >execute_num: 21
run 【T】 strategy "DD"
Worker 0 received shutdown message.
work 3 = >execute_num: 22
run 【T】 strategy "EE"
Worker 3 received shutdown message.
work 2 = >execute_num: 23
run 【T】 strategy "FF"
------Shutting down worker 1 i:1 -----------
Worker 2 received shutdown message.
work 1 = >execute_num: 24
run 【T】 strategy "GG"
Worker 1 received shutdown message.
------Shutting down worker 2 i:2 -----------
------Shutting down worker 3 i:3 -----------