If vs Case statements

Question

Are there any performance differences between using if-else and case statements when handling multiple conditions?

Which is preferred?

Answer 1

Use the one that's most readable in the given context.

Answer 2

In some languages, like C, switch may possibly be faster because it's usually implemented with a jump table. Modern compilers sometimes are smart enough to use one for several ifs as well, though.

And anyway it probably won't matter, micro optimizations are (almost) never useful.

Answer 3

Some programming languages restrict when you can use switch/case statements. For example, in many C-like languages the case values must be constant integers known at compile time.

Performance characteristics may differ between the two techniques, but you're unlikely to be able to predict in advance what they are. If performance is really critical for this code in your application, make sure you profile both approaches before deciding, as the answers may surprise you.

Normally, performance differences will be negligible, and you should therefore choose the most readable, understandable and maintainable code, as you should in pretty much any other programming situation.

Answer 4

When you have more than one ifelse, I recommend switch/select. Then again, it doesn't always work.

Suppose you something like that (not recommended but for example only)

If a > 0 and b > 0 then

' blabla
ElseIf b = -5 then

' blabla2
ElseIf a = -3 and b = 6 then

End If

Using a switch/select is NOT the way to go. However, when querying for a specific value for a variable like this

select case a

        case 1:
           ' blabla
        case 2:
           ' blabla2
        case 3:
           ' blabla3
        case 4:
           ' blabla4
        case else:
end select

In those case, I highly recommend it because it is more readable for other people.

Answer 5

I will add to some of the answers here. This is not a performance question, and if you are really concerned about performance... write a test and see which is faster.

However, this should be a question about which is proper to use, not which is better. If you have multiple if/else statements then do yourself a favor and use a case statement. If it is a simple if/else then use an if/else. You'll thank yourself later.

Answer 6

case or switch statements are really just special cases of "if .. elseif..." structures that you can use when the same object is being compared to a different simple value in every branch, and that is all that is being done. The nice thing about using them is that most compilers can implement them as jump tables, so effectively the entire 200 (or however many) branch checks can be implemented as a single table indexing operation, and a jump.

For that reason, you'd want to use a case statement when you

1. can and
2. have a fairly large number of branches.

The larger the number of "elseif"s, the more attractive a case statement is.

Answer 7

Case statements are generally preferred for readability and are generally faster if there is any speed difference, but this does not apply to every possible environment.

You could probably write a test that shows which is faster for your environment, but be careful with caching and compiler optimizations.