When is multi-threading not a good idea? [closed]

Answer 1

1. On a single processor machine and a desktop application, you use multi threads so you don't freeze the app but for nothing else really.
2. On a single processor server and a web based app, no need for multi threading because the web server handles most of it.
3. On a multi-processor machine and desktop app, you are suggested to use multi threads and parallel programming. Make as many threads as there are processors.
4. On a multi-processor server and a web based app, no need again for multi threads because the web server handles it.

In total, if you use multiple threads for other than un-freezing desktop apps and any other generic answer, you will make the app slower if you have a single core machine due to the threads interrupting each other.

Why? Because of the hardware switches. It takes time for the hardware to switch between threads in total. On a multi-core box, go ahead and use 1 thread for each core and you will greatly see a ramp up.