switch case question

André.Bisseret Andre.Bisseret at inria.fr
Fri Nov 3 14:46:31 EST 2006


Hi Mark,

On Mac pro  OS X  10.4.8 (2.16 GHz Intel Core Duo)
I get :
for "if then else" : 95-96 milliseconds
for "switch" : 12-13 milliseconds

Best regards from Grenoble
André

Le 3 nov. 06 à 20:14, Mark Smith a écrit :

> Kay, I meant to check this out when I saw your post, but it's taken  
> me a little time to get to it. I'm pretty sure that for multiple  
> choice situations, a switch structure seems more efficient (ie.  
> faster) than an equivalent multi-way if-then-else structure.
>
> I'd be interested to see if you get similar results to mine if you  
> paste the following into a button:
>
> on mouseUp
>   repeat 100000
>     put random(6) & cr after rList
>   end repeat
>
>   put the millisecs into st
>
>   repeat for each line L in rList
>     if L = 1 then
>       get 1
>     else if L = 2 then
>       get 2
>     else if L = 3 then
>       get 3
>     else if L = 4 then
>       get 4
>     else if L = 5 then
>       get 5
>     else if L = 6 then
>       get 6
>     end if
>
>     --    switch L
>     --    case 1
>     --      get 1
>     --      break
>     --    case 2
>     --      get 2
>     --      break
>     --    case 3
>     --      get 3
>     --      break
>     --    case 4
>     --      get 4
>     --      break
>     --    case 5
>     --      get 5
>     --      break
>     --    case 6
>     --      get 6
>     --      break
>     --    end switch
>   end repeat
>
>   put the millisecs - st
> end mouseUp
>
> When I do this, (Mac 1.5Mhz G4 laptop), the if-then-else version  
> takes 180-ish milliseconds, whereas the switch-case version takes  
> 70-ish ms.
> Admittedly, this isn't the difference between unusably slow and  
> blisteringly fast, but it's always worth knowing your options....
>
> Best,
>
> Mark
>
> On 31 Oct 2006, at 11:22, Kay C Lan wrote:
>
>> I've come into this a little late, no internet for a week or so, but
>> be aware that switch is slower than if-then-else-end if, no matter  
>> who
>> many nested ifs are required to do 'the same' as a mult-case switch
>> statement. It's only a couple of milliseconds over 1000 executions,
>> but it is slower.
>
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