Is Threading Necessary/Useful?

Basically, I'm wondering if threading is useful or necessary, or possibly more specifically the uses and situations in which you开发者_如何学运维 would use it. I don't know much about threading, and have never used it (I primarily use C#) and have wondered if there are any gains to performance or stability if you use them. If anyone would be so kind to explain, I would be grateful.

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In the world of desktop applications (my domain), threading is a vital construct in creating responsive user interfaces. Whenever a time-or-computationally-intensive operation needs to run, it's almost essential to run that operation in a separate thread. Otherwise, the user interface locks up and, in some cases, Windows will decide that the whole application has become unresponsive.

Threading is also a vital tool in animation, audio and communications. Basically, any situation in which you find yourself needing to do several things at once lends itself to the use of threads.

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there is definitely no gains to stability :). I would suggest you get a basic understanding of threading but don't jump to use it in any real production application until you have a real need. you have C# so not sure if you are building websites or winforms.

Usually the firsty threading use case for winforms is when a user click a button and you want to run some expensive operation (database or webservice call) but you dont want the screen to freeze up . .

a good tutorial to deal with that situation is to look at the backgroundworker class in c# as this will give you a first flavor into this space and then you can go from there

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There was a time when our applications would speed up when we deploy them on new CPU. And that speed up was by large extent because CPU speed (clock) was incremented by large factors.

But several years ago, CPU manufacturers stopped increasing CPU clocks because of physical limits (e.g. heat dissipation). And instead they started adding additional cores to CPUs.

Now, if your application runs only on one thread it cannot take advantage of complete CPU (e.g. of 4 cores it uses only 1).

So today to fully utilize CPU we must take effort and divide task on multiple treads. For ASP.NET this is already done for us by ASP.NET architecture and IIS.

Look here The Free Lunch Is Over: A Fundamental Turn Toward Concurrency in Software

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Here is a simple example of how threading can improve performance. You have a n numbers that all needed to be added together. In a single threaded application, it will take a n time units to add all of the numbers together for the final sum. However, if you broke your numbers into 2 groups, you could have the same operation running side by side with, each with a group of n/2 numbers. Each would take n/2 time units to find their respective sums, and then an additional unit to find the full sum. By creating two threads, you have effectively cut the compute time in half.

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Technically on a single core processor, there is no such thing as multi-threading, just the illusion that multiple tasks are happening in parallel since each task gets a small amount of time.

However, that being said, threading is very useful if you have to do some work that takes a long time but you want your application to be responsive (i.e. be able to do other things) while you wait for that task to finish. A good example is GUI applications.

On multi-core / multi-processor systems, you can have one process doing many things at once so the performance gain there is obvious :)