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GCD线程方面的总结

GCD线程方面的总结

作者: LoveToday2020 | 来源:发表于2019-12-15 23:28 被阅读0次

/// 串行队列+异步 == 只会开启一个线程，且队列中所有的任务都是在这个线程中执行

    NSLog(@"start");

    dispatch_queue_t queue = dispatch_queue_create("tandem queue", DISPATCH_QUEUE_SERIAL);

    dispatch_async(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=1 %@", [NSThread currentThread]);

        }

    });

    dispatch_async(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=2 %@", [NSThread currentThread]);

        }

    });

    dispatch_async(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=3 %@", [NSThread currentThread]);

        }

    });

    dispatch_async(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=4 %@", [NSThread currentThread]);

        }

    });

    NSLog(@"over");

打印结果

2019-12-15 22:45:27.729800+0800 OpenGL-OC[10476:494038] start

2019-12-15 22:45:27.729935+0800 OpenGL-OC[10476:494038] over

2019-12-15 22:45:27.730002+0800 OpenGL-OC[10476:494074] result=1 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.730125+0800 OpenGL-OC[10476:494074] result=1 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.730207+0800 OpenGL-OC[10476:494074] result=2 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.730308+0800 OpenGL-OC[10476:494074] result=2 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.731054+0800 OpenGL-OC[10476:494074] result=3 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.731173+0800 OpenGL-OC[10476:494074] result=3 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.731277+0800 OpenGL-OC[10476:494074] result=4 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

2019-12-15 22:45:27.731355+0800 OpenGL-OC[10476:494074] result=4 <NSThread: 0x6000031ac140>{number = 3, name = (null)}

结果可以看出来串行队列的异步执行操作是在一个线程中执行的，而且是start->over

才到中间的任务的执行

同步+串行

// 同步+串行队列

- (IBAction)synAndConCurrentAction:(id)sender {

    NSLog(@"start");

    dispatch_queue_t queue = dispatch_queue_create("tandem queue", DISPATCH_QUEUE_SERIAL);

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=1 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=2 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=3 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=4 %@", [NSThread currentThread]);

        }

    });

    NSLog(@"over");

}

执行的结果

2019-12-15 23:05:39.175488+0800 OpenGL-OC[10688:509594] start

2019-12-15 23:05:39.175677+0800 OpenGL-OC[10688:509594] result=1 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.175767+0800 OpenGL-OC[10688:509594] result=1 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.175854+0800 OpenGL-OC[10688:509594] result=2 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.175945+0800 OpenGL-OC[10688:509594] result=2 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.176039+0800 OpenGL-OC[10688:509594] result=3 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.176139+0800 OpenGL-OC[10688:509594] result=3 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.176452+0800 OpenGL-OC[10688:509594] result=4 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.176673+0800 OpenGL-OC[10688:509594] result=4 <NSThread: 0x600002914c00>{number = 1, name = main}

2019-12-15 23:05:39.176888+0800 OpenGL-OC[10688:509594] over

同一个线程，顺序执行与异步加串行不同的是start ->任务->over

同步+并行

/// 同步+并发

- (IBAction)syncAndConcurrentAction:(id)sender {

    NSLog(@"start");

    dispatch_queue_t queue = dispatch_queue_create("concurrent queue", DISPATCH_QUEUE_CONCURRENT);

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=1 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=2 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=3 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=4 %@", [NSThread currentThread]);

        }

    });

    NSLog(@"over");

}

执行的结果

2019-12-15 23:22:02.916509+0800 OpenGL-OC[10963:525984] start

2019-12-15 23:22:02.916689+0800 OpenGL-OC[10963:525984] result=1 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.916781+0800 OpenGL-OC[10963:525984] result=1 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.916858+0800 OpenGL-OC[10963:525984] result=2 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.916941+0800 OpenGL-OC[10963:525984] result=2 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.917017+0800 OpenGL-OC[10963:525984] result=3 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.917110+0800 OpenGL-OC[10963:525984] result=3 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.917307+0800 OpenGL-OC[10963:525984] result=4 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.918385+0800 OpenGL-OC[10963:525984] result=4 <NSThread: 0x600000365400>{number = 1, name = main}

2019-12-15 23:22:02.918647+0800 OpenGL-OC[10963:525984] over

异步+并发

NSLog(@"start");

    dispatch_queue_t queue = dispatch_queue_create("concurrent queue", DISPATCH_QUEUE_CONCURRENT);

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=1 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=2 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=3 %@", [NSThread currentThread]);

        }

    });

    dispatch_sync(queue, ^{

        for(inti =0; i <2; i++) {

            NSLog(@"result=4 %@", [NSThread currentThread]);

        }

    });

    NSLog(@"over");

执行结果

2019-12-15 23:26:43.871373+0800 OpenGL-OC[11049:531697] start

2019-12-15 23:26:43.871500+0800 OpenGL-OC[11049:531697] over

2019-12-15 23:26:43.871673+0800 OpenGL-OC[11049:531797] result=1 <NSThread: 0x6000015119c0>{number = 3, name = (null)}

2019-12-15 23:26:43.871675+0800 OpenGL-OC[11049:531798] result=2 <NSThread: 0x600001511800>{number = 4, name = (null)}

2019-12-15 23:26:43.871695+0800 OpenGL-OC[11049:531799] result=4 <NSThread: 0x600001513c80>{number = 6, name = (null)}

2019-12-15 23:26:43.871706+0800 OpenGL-OC[11049:531800] result=3 <NSThread: 0x600001513cc0>{number = 5, name = (null)}

2019-12-15 23:26:43.871800+0800 OpenGL-OC[11049:531798] result=2 <NSThread: 0x600001511800>{number = 4, name = (null)}

2019-12-15 23:26:43.871840+0800 OpenGL-OC[11049:531797] result=1 <NSThread: 0x6000015119c0>{number = 3, name = (null)}

2019-12-15 23:26:43.872026+0800 OpenGL-OC[11049:531799] result=4 <NSThread: 0x600001513c80>{number = 6, name = (null)}

2019-12-15 23:26:43.872176+0800 OpenGL-OC[11049:531800] result=3 <NSThread: 0x600001513cc0>{number = 5, name = (null)}

从执行的结果来看，执行的顺序是不确定的，并且开辟了新的线程

信号量+异步

异步执行完任务之后再回到主线程

在不引入信号量的时候

 - (IBAction)signalAndAsyn:(id)sender {

    dispatch_group_t group = dispatch_group_create();

    dispatch_queue_t queue = dispatch_queue_create("concurrent.queue", DISPATCH_QUEUE_CONCURRENT);

dispatch_group_async(group, queue, ^{

        NSLog(@"task1 start %@", [NSThread currentThread]);

        dispatch_async(queue, ^{

            NSLog(@"task1 end %@", [NSThread currentThread]);

        });

    });

    dispatch_group_async(group, queue, ^{

        NSLog(@"task2 start %@", [NSThread currentThread]);

        dispatch_async(queue, ^{

            NSLog(@"task2 end %@", [NSThread currentThread]);

        });

    });

    dispatch_group_notify(group, queue, ^{

        NSLog(@"通知");

    });

}

得到打印的结果

2019-12-16 23:14:03.728052+0800 OpenGL-OC[12427:126854] task2 start <NSThread: 0x600003dddbc0>{number = 4, name = (null)}

2019-12-16 23:14:03.728058+0800 OpenGL-OC[12427:126852] task1 start <NSThread: 0x600003ddc680>{number = 3, name = (null)}

2019-12-16 23:14:03.728215+0800 OpenGL-OC[12427:126852] task1 end <NSThread: 0x600003ddc680>{number = 3, name = (null)}

2019-12-16 23:14:03.728282+0800 OpenGL-OC[12427:126854] 通知

2019-12-16 23:14:03.728258+0800 OpenGL-OC[12427:126855] task2 end <NSThread: 0x600003ddb700>{number = 5, name = (null)}

如果我们加入信号量

dispatch_group_t group = dispatch_group_create();

    dispatch_queue_t queue = dispatch_queue_create("concurrent.queue", DISPATCH_QUEUE_CONCURRENT);

    dispatch_group_async(group, queue, ^{

        dispatch_semaphore_t sema = dispatch_semaphore_create(0);

        NSLog(@"task1 start %@", [NSThread currentThread]);

        dispatch_async(queue, ^{

            NSLog(@"task1 end %@", [NSThread currentThread]);

            dispatch_semaphore_signal(sema);

        });

        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);

    });

    dispatch_group_async(group, queue, ^{

        dispatch_semaphore_t sema = dispatch_semaphore_create(0);

        NSLog(@"task2 start %@", [NSThread currentThread]);

        dispatch_async(queue, ^{

            NSLog(@"task2 end %@", [NSThread currentThread]);

            dispatch_semaphore_signal(sema);

        });

        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);

    });

    dispatch_group_notify(group, queue, ^{

        NSLog(@"通知");

    });

打印结果

2019-12-16 23:20:29.963738+0800 OpenGL-OC[12663:134686] task2 start <NSThread: 0x600003002ec0>{number = 4, name = (null)}

2019-12-16 23:20:29.963731+0800 OpenGL-OC[12663:134685] task1 start <NSThread: 0x600003000180>{number = 3, name = (null)}

2019-12-16 23:20:29.963946+0800 OpenGL-OC[12663:134684] task2 end <NSThread: 0x600003003280>{number = 5, name = (null)}

2019-12-16 23:20:29.963947+0800 OpenGL-OC[12663:134683] task1 end <NSThread: 0x600003002dc0>{number = 6, name = (null)}

2019-12-16 23:20:29.964057+0800 OpenGL-OC[12663:134686] 通知

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