Just a nitpicky question

This is a discussion on Just a nitpicky question within the C++ Programming forums, part of the General Programming Boards category; Hey, I just thought of a really really nitpicky question. Does the ! operator (it is an operator, right?) make ...

  1. #1
    Carnivore ('-'v) Hunter2's Avatar
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    Talking Just a nitpicky question

    Hey, I just thought of a really really nitpicky question. Does the ! operator (it is an operator, right?) make any difference in speed whatsoever? I mean, would there be any difference at all in the speed of these code examples?

    Code:
    //Clip 1
    bool done = false;
    while(!done)
         //stuff
    
    //Clip 2
    bool notDone = true;
    while(notDone)
         //stuff
    It doesn't really matter to me, and I know that most people would use the first code example, but just had a sudden curiosity attack.
    Just Google It. √

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  2. #2
    ¡Amo fútbol!
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    Some speed... probably.

    Noticeable... not really


    However, your compiler might optimize something like that.

  3. #3
    I lurk
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    I'm going to say no.
    In assembly that's just a difference of conditional jumps. JE vs. JNE (Jump if Equal, Jump if Not Equal)
    This is what VC6 output:

    Code:
    while (!done)
    0040117C  mov	eax,dword ptr [ebp-4]
    0040117F  and	eax,0FFh
    00401184  test	eax,eax
    00401186  jne	main+48h
    Code:
    while (notdone)
    0040117C  mov	eax,dword ptr [ebp-4]
    0040117F  and	eax,0FFh
    00401184  test	eax,eax
    00401186  je	main+48h
    As you can see, the only difference between the two is the different jumps. I doubt one is any faster than the other.

  4. #4
    Code Goddess Prelude's Avatar
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    >I mean, would there be any difference at all in the speed of these code examples?
    Before optimization, possibly, after optimization, I would be very surprised.

    -Prelude
    My best code is written with the delete key.

  5. #5
    Carnivore ('-'v) Hunter2's Avatar
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    Ok, thanks my curiosity is satisfied.
    Just Google It. √

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