Published: Aug 26, 2011 by Midwire
In this edition of Ruby Performance I take a look at case vs. if-elsif.
In my testing, links below, it is clear that case statements are consistently more expensive than if-elsif. The difference in a single call is insignificant, but that difference adds up over time to possibly matter.
I am certainly not recommending that you use if-elsif in every instance. There are times when the trade-off may be worth the difference in performance.
Case
Case offers less typing, but implicitly compares using the more expensive === operator. Case may also offer more concise code when determining if a value falls within a range of values or a non-contiguous set of multiple values. Case code also looks prettier in most instances.
If - Elsif - Else
If-elsif-else offers speed of execution and more conspicuous code in some instances. But the fact remains that it is always faster than case.
Here are the timing summaries for strings:
Timings for [case when using strings]
Total: 3.587024
Timings for [if elsif else using strings]
Total: 2.380505
Here are the summaries for integers
Timings for [case when using integers]
Total: 3.495027
Timings for [if elsif else using integers]
Total: 2.570731
I also wanted to see the difference between the === operator with if-elsif and case which implicitly uses ===
Timings for [case when using integers]
Total: 3.495027
Timings for [if elsif else using integers with ===]
Total: 3.561783
So in this case, no pun intended, the case statement is faster slower.
Find the tests here: https://github.com/midwire/ruby-profiles/raw/master/case_vs_if.rb
Regards,
– Midwire