Performance of If-else if tree vs. Switch (multiple variables) in C#

Jure

The text of this article is not in this database — only its details are. The old site it was published on is gone, but the Internet Archive kept a copy: Performance of If-else if tree vs. Switch (multiple variables) in C#

C#If-else if treeIf-else if tree vs. Switch (multiple variables) in C#Switch (multiple variables) in C#

5 Comments

Join the conversation! Your thoughts help the community grow.

FireMyst12y ago
This is a good article. I like how you laid out the code, It would be better too if you did benchmark tests against all three constructs like this blog: http://cc.davelozinski.com/c-sharp/what-is-the-fastest-conditional-statement I've personally found the nested switch/case statements slower than their if/else equivalents.
lgsalamon16y ago
try this : static void newswitchtest() { Stopwatch timer; timer = Stopwatch.StartNew(); timer.Stop(); int bin; timer.Start(); for (int i = 0; i < 100000000; ++i) { for (int a = 0; a < 2; ++a) { for (int b = 0; b < 2; ++b) { for (int c = 0; c < 2; ++c) { bin = a + (b << 1) + (c << 2); switch (bin) { case 0: break; case 1: break; case 2: break; case 3: break; case 4: break; case 5: break; case 6: break; case 7: break; } } } } } timer.Stop(); Console.WriteLine(timer.ElapsedMilliseconds.ToString()); } My tests : 9704 ms if/else 8251 ms switch 5817 ms the code above Good article.
- Jure16y agoedited
  Thanks for the reply! The only problem with that is that first you have convert n-choice variable to [0, n-1] interval, then shift the value - which is what conditional operator (?) does in one step without performing any arithmetic or bitwise operations with values, but simply by checking the values against certain criteria. For example, two variables below can't use shift operators: int apples = 12 // number of apples - ternary (few, moderate, a lot) bool mature = false // is eatable? - binary (true, false) int situation = (apples < 5 ? 0 : (apples <= 10 ? 1 : 2)) + (mature ? 3 : 0); switch(situation) { case 0: // few uneatable apples case 1: // moderate number of uneatable apples case 2: // a lot of uneatable apples ---> this get's executed case 3: // few tasty apples case 4: // moderate number of tasty apples case 5: // a lot of tasty apples }
Sam Hobbs16y ago
Another possibility would be to create an array of methods using a delegate type and then instead of using a switch, just index into the array. That could be quite efficient if there are more than 3 conditions, right?
- Jure16y ago
  Good thinking. The performance isn't that good, though, if-tree was quite faster when I tested it. Of course I called the delegate methods in the if-tree too. The reason must be in addition. If-tree checks 3 values, then calls appropriate method, while the array of delegate-methods has to check values and calculate the index too. BIG advantage is far less code, and clarity, also easy to maintain. I will definitely use array of delegates from now on, unless I have to make the program repeat the checking a whole bunch of times, like I did when testing. Thanks for the comment!