What is faster and is there any difference?

**yann** · 10-09-2010

So, I'm working with an Arduino.

I want to edit some of the core functions and i need to know - what is faster, a "for" or a "while" loop?

Code:

while(1)
{
     do;
};

Code:

for(;;)
{
     do;
}

Which one of these will "do" faster? And maybe there is a faster way of looping things?

**VirtualAce** · 10-09-2010

What? Is this a serious question?

**yann** · 10-09-2010

...Yeah?

**whiteflags** · 10-09-2010

If this is the first place you looked to optimize, have you scrutinized how an Arduino works, and tried to do any of that faster? All the looping code is is trivial for the computer to do.

**BMJ** · 10-09-2010

Put loops inside your loops to make them faster:

Code:

while (true)
{
   while (true)
   {
      while (true)
      {
         // uber-fast!
      }
   }
}

**yann** · 10-09-2010

Lol that made me laugh... No really i had no idea, I guess I'm an idiot right now...

**yann** · 10-09-2010

Well I thank god no one on Failblog is a programmer...

I taught that the 'for' loop maybe needs to check if the iterator needs to be changed, and if you let the program run for like zillion years maybe it will be late for a few seconds, i don't know... Thats why i asked you guys.

**Elysia** · 10-09-2010

"Premature optimization is the root of much evil."
That is a great quote, and I suggested you heed it.

**Syscal** · 10-09-2010

My attempt at a serious answer.

I would assume that for(;

would be faster. My rational is that the "while(1) loop would need to be checked each time through for "1" each iteration through. Beyond that I doubt there would be any speed gain.

**iMalc** · 10-10-2010

For a brandead compiler with all optimisations off, that might be the case. But for every other case it wont make the slightest bit of difference.
for(;;) is slightly better though imho as it avoids a warning on certain compilers with certain warnings enabled.

**Salem** · 10-10-2010

Unless the body of the loop is comparable in duration to the empty loop (in other words, anything more complex than an empty if statement), then the time taken for the loop itself will be insignificant to the amount of work the loop is doing.

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What is faster and is there any difference?