Is "else if" faster than "switch() case"? [duplicate]

Question

I'm an ex Pascal guy, currently learning C#. My question is the following:

Is the code below faster than making a switch?

int a = 5;  if (a == 1) {     .... } else if(a == 2) {     .... } else if(a == 3) {     .... } else if(a == 4) {     .... } else     .... 

And the switch:

int a = 5;  switch(a) {     case 1:         ...         break;      case 2:         ...         break;      case 3:         ...         break;      case 4:         ...         break;      default:         ...         break;   } 

Which one is faster?

I'm asking, because my program has a similar structure (many, many "else if" statements). Should I turn them into switches?

Answer 1

For just a few items, the difference is small. If you have many items you should definitely use a switch.

If a switch contains more than five items, it's implemented using a lookup table or a hash list. This means that all items get the same access time, compared to a list of if:s where the last item takes much more time to reach as it has to evaluate every previous condition first.

Answer 2

Why do you care?

99.99% of the time, you shouldn't care.

These sorts of micro-optimizations are unlikely to affect the performance of your code.

Also, if you NEEDED to care, then you should be doing performance profiling on your code. In which case finding out the performance difference between a switch case and an if-else block would be trivial.

Edit: For clarity's sake: implement whichever design is clearer and more maintainable. Generally when faced with a huge switch-case or if-else block the solution is to use polymorphism. Find the behavior that's changing and encapsulate it. I've had to deal with huge, ugly switch case code like this before and generally it's not that difficult to simplify. But oh so satisfying.