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I have a question about the for and while loops, as we have to travel a value until a condition is met. I wonder which is more efficient at low level, and why?

That is, these two codes give the same result:

FOR:

for (int i = 0; i<10 ; i++)
{
    if (i==4)
    {
        return;
    }
}

WHILE:

int i=0;
while (i<10 and i!=4)
{
    i++;
}

This is a small example of a possible loop, and we could be looking at a record of thousands.

What code is more effective? I've always said that I have to use a while in this case, but I wonder if a low level is still better while or better yet is for.

Thank you very much.

leoledmag
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    How would `i` ever get to be more than `4`? And shouldn't the `return` actually be `break` if you want the two to have the same result? – nnnnnn Nov 09 '13 at 01:27
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    Always favour readability. At least until you can prove one is significantly faster. – tangrs Nov 09 '13 at 01:27
  • how about just `i = 4; return;`? :P You already know the exact state you should be in when you exit the loop, and don't do anything within it. There's nothing that needs deciding. – cHao Nov 09 '13 at 01:27
  • You know a `for` is just a convenient way for the programmer to write an iterated `while` and results in identical bytecode being generated, right? – Ray Stojonic Nov 09 '13 at 01:30

3 Answers3

4

The answer is: it doesn't matter.

You will not see any difference in performance in either, unless you really try hard to make code to see the difference, and what really matters is the readability of your code (and this is where you'll save time and and money in the future), so use whichever one is more understandable.

In your case, i'll suggest the While approach ...

I'll also suggest reading this article by Eric Lippert: How Bad Is Good Enough?, just in case you're not sold on the readability vs. silly optimizations :)

Community
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Noctis
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  • I tend to prefer while as well. I think while is a bit easier to use than for and looks easier on the eyes. Readability is key here. – JaidynReiman Nov 09 '13 at 01:30
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They should compile very similarly. At a low level you are looking at executing the commands within the loop, and then you will have two calls to compare a value and jump to the next block of code if the condition calls for exiting the loop.

As mentioned above, while should lead to better readability and thus is the better choice.

Cam
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1

Both for and while are the same.

The only difference is where you place the condition. internally the while loop uses the 'for' syntax in low level.

In your scenario. While is the best option ** if you don't know the upper limit **

you can use 

While(i!=4)
{
 i++
}

Use for loop if you know the upper limit, else while is the best friend.

Rajshekar Reddy
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