If statements vs case

Hershel Fisch hershf at rgllc.us
Mon Feb 26 15:11:51 EST 2007


On 2/26/07 1:50 PM, "Jim Ault" <JimAultWins at yahoo.com> wrote:

> 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
I thought you are talking about accumulating real "dollars" LOL
> :-)
> 
> 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
>> 
>> 
>> 
> 
> 
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