semaphores

简明释义

英[ˈsɛm.ə.fɔːrz]美[ˈsɛməfɔrz]

n. 信号；[计]信号量；旗语；信号灯（semaphore 的复数）

v. 用信号向……发出；打旗语（semaphore 的三单形式）

英英释义

单词用法

同义词

反义词

例句

1.Specifically, semaphores ensure that a server completes certain tasks before it begins other tasks.

具体地说，信号量确保服务器完成某些任务，然后再开始其他任务。

2.Named semaphores extend the synchronization between processes.

有名信号量可以在进程之间进行同步。

3.Other systems: the gestures that mimes use, semaphores, are all semiotic systems.

其他的系统，比如手势，模仿，信号，他们都是符号系统。

4.Linux POSIX semaphores use sem_wait to suspend the calling thread until the semaphore has a non-zero count.

LinuxPOSIX信号使用sem_wait来挂起发出调用的线程，直到信号拥有了非零的计数值。

5.Timeout: Win32 event semaphores support timed wait.

超时：Win32事件信号支持定时等待。

6.It should be noted that the maximum semaphores systemwide (semmns) is equal to.

注意，系统范围内最多信号量个数(semmns)等于。

7.Refer to the section on semaphores in this article for the prototype for each of these System V semaphores.

关于每个SystemV信号量的原型，请参阅本文中有关信号量一节的内容。

8.The system uses semaphores to control access to shared resources.

该系统使用信号量来控制对共享资源的访问。

9.The traffic lights are controlled by semaphores to manage vehicle flow.

交通信号灯由信号量控制，以管理车辆流量。

10.A binary semaphore can be used as a simple lock.

二进制信号量可以用作简单的锁。

11.When a thread waits on a semaphore, it is temporarily blocked.

当一个线程在信号量上等待时，它会被暂时阻塞。

12.In multithreading, semaphores help prevent race conditions.

在多线程中，信号量有助于防止竞争条件。

作文

In the world of computer science and programming, synchronization is a crucial aspect that ensures multiple processes or threads can operate without interfering with each other. One of the key tools used for this purpose is known as semaphores, which play a significant role in managing access to shared resources. To understand how semaphores work, it is essential to delve into their definition and practical applications. Semaphores are essentially signaling mechanisms that help control access to a common resource in a concurrent system. They were first introduced by Edsger Dijkstra in the 1960s and have since become a fundamental concept in operating systems and concurrent programming. A semaphore maintains a count that represents the number of available resources. When a process wants to access a resource, it must first check the value of the semaphore. If the value is greater than zero, the process can proceed, and the semaphore is decremented. Conversely, if the value is zero, the process must wait until a resource becomes available, at which point the semaphore is incremented, allowing the waiting process to continue. There are two main types of semaphores: binary and counting. A binary semaphore can only take the values of 0 and 1, making it similar to a mutex (mutual exclusion). It is commonly used to ensure that only one process can access a critical section of code at any given time. On the other hand, a counting semaphore can take on a range of values, allowing multiple processes to access a limited number of instances of a resource simultaneously. This flexibility makes counting semaphores particularly useful for managing pools of resources, such as database connections or thread pools. The importance of semaphores cannot be overstated, especially in multi-threaded environments where resource contention can lead to deadlocks and race conditions. By using semaphores, developers can implement more robust and efficient programs that are less prone to such issues. For instance, in a web server handling multiple requests simultaneously, semaphores can be employed to limit the number of concurrent database connections, ensuring that the server does not become overwhelmed and can serve users effectively. Despite their benefits, semaphores also come with challenges. Improper use can lead to problems like deadlocks, where two or more processes are waiting indefinitely for resources held by each other. Therefore, it is vital for programmers to design their systems carefully, implementing semaphores with a clear understanding of their behavior and potential pitfalls. Additionally, debugging issues related to semaphores can be complex due to the non-deterministic nature of concurrent execution. In conclusion, semaphores are a powerful tool in the realm of concurrent programming, providing a means to manage access to shared resources effectively. Their ability to prevent conflicts and ensure smooth operation in multi-threaded environments makes them indispensable for modern software development. However, with great power comes great responsibility; developers must use semaphores judiciously to avoid complications like deadlocks and race conditions. As technology continues to evolve, the understanding and application of semaphores will remain a critical skill for programmers aiming to build efficient and reliable systems.

在计算机科学和编程的世界中，同步是确保多个进程或线程可以不互相干扰地运行的关键方面。为此，使用的一个重要工具被称为信号量，它在管理对共享资源的访问方面发挥着重要作用。要理解信号量的工作原理，有必要深入探讨其定义和实际应用。信号量本质上是一种信号机制，用于控制并发系统中对公共资源的访问。它们首次由Edsger Dijkstra在20世纪60年代引入，此后成为操作系统和并发编程中的基本概念。信号量维护一个计数值，表示可用资源的数量。当进程想要访问资源时，必须先检查信号量的值。如果值大于零，则进程可以继续，并且信号量会递减。相反，如果值为零，则进程必须等待，直到资源变得可用，此时信号量会递增，允许等待的进程继续。信号量主要有两种类型：二进制信号量和计数信号量。二进制信号量只能取0和1的值，使其类似于互斥锁（互斥）。它通常用于确保在任何给定时间只有一个进程可以访问临界代码区。另一方面，计数信号量可以取一系列值，允许多个进程同时访问有限数量的资源实例。这种灵活性使得计数信号量特别适用于管理资源池，例如数据库连接或线程池。信号量的重要性不容小觑，尤其是在多线程环境中，资源争用可能导致死锁和竞态条件。通过使用信号量，开发人员可以实现更健壮和高效的程序，从而减少这些问题的发生。例如，在处理多个请求的网络服务器中，可以使用信号量限制并发数据库连接的数量，以确保服务器不会过载，并能够有效地为用户服务。尽管有其好处，信号量也带来了挑战。不当使用可能导致死锁等问题，其中两个或多个进程无限期等待彼此持有的资源。因此，对于程序员来说，仔细设计系统至关重要，实施信号量时必须清楚了解其行为和潜在陷阱。此外，由于并发执行的非确定性特征，调试与信号量相关的问题可能非常复杂。总之，信号量是并发编程领域中的一种强大工具，有效管理对共享资源的访问。它们防止冲突并确保多线程环境中平稳运行的能力使其在现代软件开发中不可或缺。然而，强大的工具伴随着巨大的责任；开发人员必须谨慎使用信号量以避免死锁和竞态条件等复杂问题。随着技术的不断发展，对信号量的理解和应用将始终是程序员构建高效和可靠系统的关键技能。