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C++ Multithreading - Basic thread creation

C++11 standard introduces integrated sublibrary for multithreading. It has been moved from Boost library. However because multithreading is very important topic in software development I decided to make multithreading tutorial as separate section of this blog.

I will not explain here theory about multithreading, but I will try to explain usage of multithreading based on thread library from C++11 standard. If theory explanation will be required for some aspects I will try to put links to separate articles explaining them.

Introduction theory about multithreading you can find on Wikipedia article here

This article will present basic threads creation and usage in C++. Code of example you can find here:
Output of the example is (it can be little other - depends how thread will be invoked by OS):
In point I we are creating new thread where print() function will be invoked. This thread will work in parallel to the main function (main application is second thread called main thread)

Point II shows printing values using for loop invoked from main thread.

Point III is invoking function join() which will wait until thread1 will finish. This is basic synchronization. Without that function there is possible that we will receive termination error if main thread finished and thread1 did not finished its job.

If we do not want to wait until thread1 will finish and do not want to receive termination error we could use detach() function (look point IV). Thanks to that function thread1 will be detached from our main application and will work in the background as deamon thread. We will be able to operate our next function without waiting for its finish if we do not need it.

Of course output of this example can be different on your machine. It depends how your OS schedule threads invoking. Threads are managed by OS so you can see different results if your threads are not synchronized properly. This is basic application so it does not contain sophisticated thread synchronization. I will explain how to synchronize threads in next articles.

This is first basic tutorial which presents how to create basic thread to run two separate function in parallel. In next multithreading articles I will show how to pass parameters for multithreading functions, return values, synchronize variables between threads and other thread-related topics.

Code of this example you can find on our GitHub account here: https://github.com/xmementoit/CppAdventureExamples/tree/master/multithreading/basicThreads

Source: http://www.javastudychannel.com/attachments/Resources/5002-23399-Multi-threaded-program.jpg

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