Brian Yennie wrote:
>
> I think what you are discovering is that "it depends". I noticed a
> couple of things with your example:
>
> 1) Your switch conditions are all expressions that need to be
> reevaluated in every iteration (as opposed to constant value). This
> effectively kills the switch statement's ability to "jump" to the
> correct result - since it has to reevaluate the "jumps" every time
> through. Try throwing in string constants and switch should start
gaining.
>
> 2) 3-4 possible results is probably around the break-even point (in
> general). But every extra condition will typically cause a gain on the
> switch side.
Brian, you are absolutely right. I changed the test to string constants
with four conditions and it was break-even. I knew there had to be
something wrong with my test the results were too different.
on mouseUp
put 100000 into tRepeats
put the milliseconds into tstart
switchTest tRepeats
put the milliseconds - tstart into item 1 of tTimes
put the milliseconds into tstart
ifTest tRepeats
put the milliseconds - tstart into item 2 of tTimes
put tTimes
end mouseUp
on switchTest pRepeats
put "a" into tRep
repeat pRepeats
switch tRep
case tRep = "aaaaa"
put tRep into x
break
case tRep = "aaaaaaaaaaa"
put tRep into x
break
case tRep = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
put tRep into x
break
default
put tRep into x
end switch
put "a" after tRep
end repeat
end switchTest
on ifTest pRepeats
put "a" into tRep
repeat pRepeats
if tRep = "aaaaa" then
put tRep into x
else if tRep ="aaaaaaaaaaa" then
put tRep into x
else if tRep = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaa" then
put tRep into x
else
put tRep into x
end if
put "a" after tRep
end repeat
end ifTest
I think the basic lesson though is that there is no general answer. It
depends a lot on your data. For example, even the same if statement can
be written to be 10 times faster or slower depending on the data.
Suppose your first if statement passes 99% of the time, as opposed to
failing all tests 99% of the time.
My general thoughts:
* Use switch statements when you have 3 or more constant expressions (or
may need to add more in the future)
* Use switch statements if you need the "fall through" logic (by
omitting break statements). Sometimes this leads to more elegant looking
code.
* Use if statements when you have complex expressions and can predict to
some degree which conditions will pass/fail most of the time
* If speed is not an issue, use whichever one makes the most sense to you
Scott Kane wrote:
----- Original Message ----- From: "J. Landman Gay"
<[EMAIL PROTECTED]>
I read somewhere a long time ago that switch statements run faster
than if/else. I think it was a general comment rather than
specifically related to Revolution programming but it was so long
ago I can't recall. Does anyone know if it is true for Rev scripts?
I haven't timed it - but if it's read by the engine in the same
manner other programming languages handle it then it would be faster
as any subsequent conditions are skipped because once the case
statement (switch statement) is met the compiler knows not to proceed
- as opposed to if/then/else etc where the entire handler is
evaluated in full.
I remember reading that Rev doesn't evaluate the entire if/else, so
I'd think it would be about the same as switch. But lookee here, I did
a test, with surprising results:
on mouseUp
put 100000 into tRepeats
put the milliseconds into tstart
switchTest tRepeats
put the milliseconds - tstart into item 1 of tTimes
put the milliseconds into tstart
ifTest tRepeats
put the milliseconds - tstart into item 2 of tTimes
put tTimes
end mouseUp
on switchTest pRepeats
put 1 into tRep
repeat pRepeats
switch tRep
case tRep > 10000
put tRep into x
break
case tRep > 5000
put tRep into x
break
case tRep > 2000
put tRep into x
break
default
put tRep into x
end switch
add 1 to tRep
end repeat
end switchTest
on ifTest pRepeats
put 1 into tRep
repeat pRepeats
if tRep > 10000 then
put tRep into x
else if tRep > 5000 then
put tRep into x
else if tRep > 2000 then
put tRep into x
else
put tRep into x
end if
add 1 to tRep
end repeat
end ifTest
The "if/else" is 4 to 5 times faster. <blink> Is my test accurate?
--
Jacqueline Landman Gay | [EMAIL PROTECTED]
HyperActive Software | http://www.hyperactivesw.com
_______________________________________________
use-revolution mailing list
[email protected]
Please visit this url to subscribe, unsubscribe and manage your
subscription preferences:
http://lists.runrev.com/mailman/listinfo/use-revolution
_______________________________________________
use-revolution mailing list
[email protected]
Please visit this url to subscribe, unsubscribe and manage your
subscription preferences:
http://lists.runrev.com/mailman/listinfo/use-revolution
--
Jacqueline Landman Gay | [EMAIL PROTECTED]
HyperActive Software | http://www.hyperactivesw.com
_______________________________________________
use-revolution mailing list
[email protected]
Please visit this url to subscribe, unsubscribe and manage your subscription
preferences:
http://lists.runrev.com/mailman/listinfo/use-revolution
