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[黑Java系列]别告诉我Java比Python还慢

2015/10/23镜像同步14 回复

题目：两个agent：ping和pong，互相通信。ping先发送初始值0。之后，两者每次收到一个数字，就将它加1发给对方。当ping接收到的值超过某个限制时结束。 Java代码： package junk.pingpong; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class PingPongTestLockCond { static class Context { Lock lock = new ReentrantLock(); long msg; boolean pingSent; Condition pingSentCond = lock.newCondition(); boolean pongSent; Condition pongSentCond = lock.newCondition(); } static class Ping implements Runnable { public Context ctx; public long curVal = 1; public long limit; public Ping(Context ctx, long limit) { this.ctx = ctx; this.limit = limit; } @Override public void run() { try { ctx.lock.lock(); while (true) { // send ctx.msg = curVal; ctx.pingSent = true; ctx.pingSentCond.signalAll(); // receive while (!ctx.pongSent) { ctx.pongSentCond.await(); // implicit unlock } ctx.pongSent = false; long newVal = ctx.msg; // update curVal = newVal + 1; // exit if (newVal >= limit) { // last message and exit ctx.msg = -1L; ctx.pingSent = true; ctx.pingSentCond.signalAll(); break; // exit } } } catch (InterruptedException e) { System.out.println("[ping] Interrupted. This should not happen."); e.printStackTrace(System.out); } finally { ctx.lock.unlock(); } } } static class Pong implements Runnable { public Context ctx; public long curVal; public Pong(Context ctx) { this.ctx = ctx; } @Override public void run() { try { ctx.lock.lock(); while (true) { // receive while (!ctx.pingSent) { ctx.pingSentCond.await(); // implicit unlock } ctx.pingSent = false; long newVal = ctx.msg; // update curVal = newVal + 1; // exit if (newVal == -1) { // exit on demand break; // exit } // send ctx.msg = curVal; ctx.pongSent = true; ctx.pongSentCond.signalAll(); } } catch (InterruptedException e) { System.out.println("[pong] Interrupted. This should not happen."); e.printStackTrace(System.out); } finally { ctx.lock.unlock(); } } } public static void main(String[] args) throws Exception { Context ctx = new Context(); Ping ping = new Ping(ctx, 5000000L); Pong pong = new Pong(ctx); Thread pingThr = new Thread(ping); Thread pongThr = new Thread(pong); long t1 = System.currentTimeMillis(); pingThr.start(); pongThr.start(); pingThr.join(); pongThr.join(); long t2 = System.currentTimeMillis(); System.out.printf("time: %dms\n", t2-t1); System.out.printf("ping.curVal = %d\n", ping.curVal); } } 运行结果： time: 37344ms ping.curVal = 5000001 Python代码： import datetime sz = 5000000 def pong(): v = yield while v >= 0: v2 = v + 1 v = yield v2 return def ping(peer): cur_val = 0 while cur_val <= sz: new_val = peer.send(cur_val) cur_val = new_val + 1 print(cur_val) n2 = pong() n2.send(None) # start it so it pauses on the first yield t1 = datetime.datetime.now() ping(n2) t2 = datetime.datetime.now() d = t2-t1 print(d) 运行结果： 5000001 0:00:01.584955

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