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

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

Shouldn't be hard to test, create a function that switches or ifelse's between 5 numbers, throw a rand(1,5) into that function and loop that a few times while timing it.

Answer 3

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.

Answer 4

Far more important than the performance benefits of switch (which are relatively slight, but worth noting) are the readability issues.

I for one find a switch statement extremely clear in intent and pure whitespace, compared to chains of ifs.

Answer 5

I'd say the switch is the way to go, it is both faster and better practise.

There are various links such as (http://www.blackwasp.co.uk/SpeedTestIfElseSwitch.aspx) that show benchmark tests comparing the two.

Answer 6

Since the switch statement expresses the same intent as your if / else chain but in a more restricted, formal manner, your first guess should be that the compiler will be able to optimize it better, since it can draw more conclusions about the conditions placed on your code (i.e. only one state can possibly be true, the value being compared is a primitive type, etc.) This is a pretty safe general truth when you are comparing two similar language structures for runtime performance.