If statements vs case

[Jim Ault]

So the bottom line is that if you are executing this IF or SWITCH you can
expect to waste....

Per trip cost is

89-74/10,000  
= 15/10,000 milliseconds
= 0.0015 milliseconds
which is 1.5 millionths of a second longer per loop to use IF

A million here, a million there, and pretty soon your talking real seconds
:-)

Thanks for the testing work.

Jim Ault
Las Vegas


On 2/26/07 9:35 AM, "Richard Gaskin" <ambassador at fourthworld.com> wrote:

> Mark Smith wrote:
>> I just ran a very simple benchmark test, which suggests that if/then
>> goes about 20% faster than switch/case.
> 
> I get different results here, but I had to rewrite the if-then test as
> the example posted as it wasn't executing the same logic as the switch
> block.  In the "if" example the "c" case didn't fall through to also
> execute the "d" case as it did in the "switch" example, and the "e" case
> wasn't handled at all.
> 
> So I wrote a fresh pair of examples that test all possible cases,
> running each full set 10000 iterations. They each produce the same
> logical result at this point, with these times on my MacBook Pro:
> 
> if:89ms switch:74ms
> if result:140000 switch result:140000
> 
> The timings aren't surprising given the extra evaluations needed to get
> the same effect using "if" as with the "switch" fall-through behavior.
> 
> Please double-check the benchmark handler below to make sure that both
> tests are using equivalent logic, and look for ways the "if-then" might
> be better optimized:
> 
> 
> 
> local sResult
> 
> on mouseUp
>    -- number of test iterations:
>    put 10000 into n
>    -- load var with all possible values:
>    put "abcde" into s
>    --
>    --
>    -- TEST 1: if-then
>    put 0 into sResult
>    put the millisecs into t
>    repeat n
>      --
>      repeat for each char tVar in s
>      If tVar ="a" or tVar ="b" then
>          DoThing1
>        else if tVar = "c" or tVar = "d" then
>          if tVar = "c" then
>            DoThing2
>          end if
>          DoThing3
>        Else If tVar ="e" then
>          DoThing4
>        End if
>      end repeat
>      --
>    end repeat
>    put the millisecs - t into t1
>    put sResult into tResult1
>    --
>    -- TEST 2: switch
>    put 0 into sResult
>    put the millisecs into t
>    repeat n
>      --
>      repeat for each char tVar in s
>        switch tVar
>        case "a"
>        case "b"
>          DoThing1
>          break
>        case "c"
>          DoThing2
>        case "d"
>          DoThing3
>          break
>        case "e"
>          DoThing4
>        end switch
>      end repeat
>      --
>    end repeat
>    put the millisecs - t into t2
>    put sResult into tResult2
>    --
>    -- show results:
>    put "if:"&t1 &"ms"&&"switch:"& t2&"ms"&cr&\
>   "if result:"& tResult1 &&"switch result:"&tResult2
> end mouseUp
> 
> 
> 
> on DoThing1
>    add 1 to sResult
> end DoThing1
> 
> on DoThing2
>    add 2 to sResult
> end DoThing2
> 
> on Dothing3
>    add 3 to sResult
> end Dothing3
> 
> on DoThing4
>    add 4 to sResult
> end DoThing4
> 
> 
>