程序在单独的线程上打印奇数和偶数 [英] program to print odd numbers and even numbers on seperate threads

问题描述

我正在学习使用pthreads进行编程. 我该如何编写一个程序来在单独的线程上打印奇数和偶数.

I am learning programming using pthreads. How can I write a program to print odd numbers and even numbers on separate threads.

推荐答案

您需要两个同步对象，例如信号量或条件变量.这个想法是线程A在打印之前请求信号A，而在线程B进行相反操作之后则释放信号B.

You need two synchronization objects such as a semaphore or a condition variable. The idea is that thread A requests semaphore A before it prints and releases semaphore B after while thread B does the opposite.

这个想法是，线程A请求信号量A之后，它将信号量降低为0.下次请求信号量A时，它将阻塞，直到线程B释放信号量为止.

The idea is that after thread A requests semaphore A, it will drop the semaphore to 0. The next time it requests semaphore A it will block until thread B releases the semaphore.

在伪代码中，这看起来像:

In pseudo code, this looks like:

initialization:
    // set semA to 1 so that the call to sem_wait in the
    // even thread will succeed right away
    sem_init(semA, 1)
    sem_init(semB, 0)

even_thread:
   to_print = 0;

   loop:
       sem_wait(semA);

       write(to_print);
       to_print += 2

       sem_post(semB)

odd_thread:
    to_print = 1

    loop:
        sem_wait(semB)

        write(to_print)
        to_print += 2

        sem_post(semA)

由于您想自学线程编程，因此我将把它转换为实际的pthreads代码.

Since you want to teach yourself threads programming, I'll leave it to you to convert this into actual pthreads code.

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