|
|
Posted by David Grant on 12/06/05 18:15
Hi,
I imagine this kind of thing is not especially taxing on the processor,
especially if the condition is a fairly simple comparison. That said, I
have very little understanding aside from my own limited experience of
what runs slowly!
If you're worried about code maintenance, then move the code out to a
function and pass the parts that vary as parameters.
Cheers,
David Grant
Steve McGill wrote:
> Hi,
> David is right about the unwanted side-effect. Thanks for the idea though.
> Unfortunately the 'greater problem' is not so great, I've just been doing
> this for a while now and find myself programming loops like these so often
> and I've never got round to testing if a simple IF statement is a major
> drain on the CPU. Somehow I doubt it.
> I got this reply from someone direct to my mail address, which seems to sum
> it up:
>
> --
> In truth you are not evaluating the whole if block just the condition
> and since its such a simple condition I can't see how it would be at
> all taxing on the server. In your specific case I can't think of a
> better way to do it either.
> --
>
> I'll try and think of a better example:
>
> <?
> $bool = true; // this is set dynamically and not known in advance
> while(true) {
> if($bool) { // this condition tested in every single loop
> // do first code
> } else {
> // do second code
> }
> }
> ?>
>
> and I am wondering if the compiler is smart enough to turn this into:
>
> <?
> $bool = true; // this is set dynamically and not known in advance
> if($bool) { // this condition only tested once
> while(true) {
> // do first code
> }
> } else {
> while(true) {
> // do second code
> }
> }
> ?>
>
> I realise this might be hard to follow without giving specific examples and
> code.
>
> In this case, the coding style of the 2nd example seems far better, but
> sometimes the 2 blocks of code are practically identical and it's a
> programmer's nightmare to have the blocks of code in 2 places and to
> remember to keep them both updated.
>
> I'm also assuming that using function calls is also much slower than
> evaluating a very simple IF statement.
>
> Thanks for your interest.
>
> Best wishes,
> Steve
>
> "David Grant" <david@grant.org.uk> schreef in bericht
> news:4395B271.4030303@grant.org.uk...
>> Jared Williams wrote:
>>> Why not
>>>
>>> for ($i = 0; $i < 1000000/100; ++$i)
>> This involves dividing 1000000 by 100 for each iteration of the loop.
>> It would be better to test against 10000.
>>
>> There is also the unwanted side-effect of executing the code on each
>> hundredth iteration, which is unwanted (as far as I understand the
>> problem). :)
>>
>> It would be interesting if Steve could divulge the greater problem that
>> he is seeking a solution to.
>>
>> Cheers,
>>
>> David
>> --
>> David Grant
>> http://www.grant.org.uk/
>
--
David Grant
http://www.grant.org.uk/
Navigation:
[Reply to this message]
|