iOS multi-threading and web Development multi-threading Overview

Last Update:2015-07-10 Source: Internet

Author: User

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Shimen The main contribution, respect the work of the author, please do not reprint.If the article is helpful to you, you are welcome to donate to the author, support the Shimen, donate the amount at random, ^_^ I want to donate: click DonateCocos2d-x source Download: Dot I teleportGames official Download:HTTP://DWZ.CN/RWTJLGame Video Preview:http://dwz.cn/RzHHdgame development Blog:Http://dwz.cn/RzJzIGame Source Transfer : Http://dwz.cn/Nret1 A. Processwhat is a process A process is an application that is running in the systemeach process is independent, and each process runs within its dedicated and protected memory spacefor example, Open qq, Xcode, the system will start 2 processes respectivelyYou can view the processes that are open in your Mac system through Activity Monitor B. Threadsmain thread, sub-thread occupy memory is 1M and 512K respectively1. What is a thread 1 processes to perform a task, a thread must be wired (at least 1 threads per 1 processes)threads are the basic unit of execution of a process, and all tasks of a process (program) are executed in the threadfor example, using a cool dog to play music, using Thunder to download movies, all need to execute in the thread 2. Thread's serialThe execution of a task in 1 threads is serial If you want to perform multiple tasks in 1 threads, You can perform these tasks sequentially, one at a-That is , at the same time, 1 threads can only perform one taskfor example, download 3 files in 1 threads (file a, file b, file c, respectively) 3. MultithreadingWhat is multithreading Multiple threads can be opened in 1 processes, each thread can perform different tasks in parallel (at the same time) Process shop, Thread shop workermultithreading technology can improve the efficiency of program executionfor example, the simultaneous opening of 3 threads to download 3 files (file a, file b, file c, respectively) 4. Multithreading PrincipleThe principle of multithreading At the same time, the CPU can only handle 1 threads, and only 1 threads are working (executing) Multi-threaded concurrency (simultaneous) execution, in fact, the CPU is quickly dispatched between multiple threads (switching) If the CPU schedules threads Fast enough, It creates the illusion of multi-threaded concurrency execution Think: What happens if the threads are very, very much? CPU will be dispatched between N multithreading, the CPU will be exhausted, consumes a lot of CPU resources The frequency at which each thread is scheduled to execute is reduced (thread execution efficiency is reduced) 5. Advantages and disadvantages of multithreadingAdvantages of multithreading To improve the execution efficiency of the program appropriately Can appropriately improve resource utilization (CPU, memory Utilization) Disadvantages of multithreading Open threads need to occupy a certain amount of memory (by default, The main thread takes up 1M, the child threads occupy 512KB), If you open a large number of threads, will consume a lot of memory space, reduce the performance of the program The more threads, the greater the overhead of the CPU on the dispatch thread Programming is more complex: such as communication between threads, multi-threaded data sharing 6. Main threadWhat is the main thread After an iOS program runs, 1 threads are turned on by default, called the "main thread" or "ui thread" Main functions of the primary thread Display \ Refresh UI interface Handling UI Events (such as click events, Scrolling events, drag events, etc.) Note on the use of the main thread Do not put more time-consuming operations into the main threadtime-consuming operations can get stuck in the main thread, seriously affecting the smoothness of the ui, giving users a "card" bad experience 7.iOS Multithreading Implementation Technology <ul style="margin: 0px 0px 0px 45px; padding: 0px; word-break: break-all; line-height: 21px;"> <ul style="margin: 0px 0px 0px 45px; padding: 0px; word-break: break-all; line-height: 21px;"> <li style="margin: 0px 0px 1em; padding: 0px; list-style: inherit !important;">Pthread</li> <li style="margin: 0px 0px 1em; padding: 0px; list-style: inherit !important;">Nsthread</li> <li style="margin: 0px 0px 1em; padding: 0px; list-style: inherit !important;">GCD</li> <li style="margin: 0px 0px 1em; padding: 0px; list-style: inherit !important;">Nsoperation</li> </ul> </ul> C. What needs to be masteredMultithreading 1.NSThread Several ways to 1> the thread * First created, then started Nsthread *thread = [[nsthread alloc] initwithtarget:self selector: @selector (run) object:nil]; [thread start]; * Direct Start [nsthread detachnewthreadselector: @selector (run) totarget:self withobject:nil]; [self performselectorinbackground: @selector (run) withobject:nil]; 2> Other uses Nsthread *current = [nsthread currentthread]; + (nsthread *) mainthread; Get the main thread 3> Inter-thread Communication Performselectoronmainthread ..... 2.GCD (focus) 1> Types of queues * Concurrent Queue Get a global concurrent queue: Dispatch_get_global_queue * Serial Queue A. Create yourself Dispatch_queue_create B. Home row Dispatch_get_main_queue 2> method types for performing tasks * Synchronization (sync) execution * Asynchronous (async) execution 3> Understanding how queues and methods work together 4> Inter-thread Communication Dispatch_async ( Dispatch_get_global_queue (dispatch_queue_priority_default, 0), ^{ Perform time-consuming asynchronous operations ... Dispatch_async (dispatch_get_main_queue (), ^{ Go back to the main thread and perform a UI refresh operation }); }); 5> Other uses Dispatch_once Dispatch_after Dispatch_group_async\dispatch_group_notify 3.NSOperation 1> Basic Use Nsinvocationoperation Nsblockoperation 2> Nsoperationqueue (key) * Maximum number of concurrent settings-(void) setmaxconcurrentoperationcount: (nsinteger) cnt; Note: This method can only limit the number of simultaneous threads, and cannot limit a particular thread (that is, the thread group that might be executed each time is Different) * Set Dependencies [OPERATIONB adddependency:operationa]; Action B depends on action a 3> customizing Operation (understanding Basic Processes) 4> How to resolve a picture (a Url) to repeat the download problem Shimen The main contribution, respect the work of the author, please do not reprint.If the article is helpful to you, you are welcome to donate to the author, support the Shimen, donate the amount at random, ^_^ I want to donate: click DonateCocos2d-x source Download: Dot I teleportGames official Download:HTTP://DWZ.CN/RWTJLGame Video Preview:http://dwz.cn/RzHHdgame development Blog:Http://dwz.cn/RzJzIGame Source Transfer : Http://dwz.cn/Nret1 Copyright Notice: This article for Bo Master original article, without Bo Master permission not Reproduced. iOS multi-threading and web Development multi-threading Overview

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