Know, I know this is mainly a calculator forum and most if not all calculators do not use threads, so I'm kind of talking to you computer programmers out there.

Let me first explain to you what multi-threading is. Multi-threading is when you create multiple threads and do various tasks in each thread simultaneously. A thread is basically an instance of code that can be called again and again as well as at the exact same time as another. Yes that means the computer doesn't wait for your update section of code to run when it needs to render.

The purpose for multi-threading is to make your games/apps/programs run more efficiently. Here is an example of a non-threaded piece of code (something you would find on a calc).




(Non-Threaded)

Game Loop
{

A bunch of calculations

Clear the screen

Render your items

Swap buffers

}



Notice that every time your loops runs, you have to wait for the game to rendering the last scene to begin the next calculation phase. Multi-threading this makes it so that you can do both at the same time (almost). One way to put this -> All of your render code works with the GPU on a computer, while the calculation code works with the CPU. If you leave them in order (one, then the other, than the other, etc) Your GPU has to wait for your CPU to finish before it can be used and visa versa. So the entire time you are rendering your CPU is literally sitting there doing absolutely nothing. If we multi-thread this, we can eliminate that inefficiency.

(Multi-Threaded)

Thread 1
{


Calculate a bunch of stuffs


}


Thread 2
{


Clear the screenRender your itemsSwap buffers

}

Thread 1 and Thread 2 run at the same time.

Now that you have separated them you will have some problems. Both threads read and/or write to example sprite SHIP. What happens if thread 2 reads the X position of SHIP while thread 1 is writing to the X position of SHIP. This is what is dangerous, and can cause glitches, crashes, and unforeseen bugs. There are several ways to present this, one of which can be explained here: http://blog.slapware.eu/game-engine/programming/multithreaded-renderloop-part1/

Another bonus to splitting the calculations from the renders is that you can put the calculation on a timer so that it runs at the same speed on all devices while not affecting the rendering in the process. (no need to calculate for CPU speed variations).