allocating structs within STL vectors

This is a discussion on allocating structs within STL vectors within the C++ Programming forums, part of the General Programming Boards category; I didn't mean a vector<double*> I meant using a vector<double> vs. double* Bottom line appears to be that I should ...

  1. #16
    The larch
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    I didn't mean a vector<double*> I meant using a vector<double> vs. double*

    Bottom line appears to be that I should use vector<double> instead of double*
    A double* and a vector<double> are theoretically just as good but with Visual C++ you may need to use some compiler flags to turn off unnecessary bounds checking for vector.

    I am writing a program that includes functions that must be lighting fast. I'm not knowledgeable in optimization techniques, so any up-front time savings help.
    Don't optimise prematurely. Write a program that works first, and then, if you are not satisfied with the performance, check what exactly is taking too long.

    That said, don't pessimize prematurely, either. Use general optimization techniques that don't make the code less readable, such as passing large objects by reference, upfront.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  2. #17
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    King Mir, you're quoting the wrong person.

  3. #18
    and the hat of sweating
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    Quote Originally Posted by anon View Post
    A double* and a vector<double> are theoretically just as good but with Visual C++ you may need to use some compiler flags to turn off unnecessary bounds checking for vector.
    I think you need to define some pre-processor symbols to turn on extra checking.
    By default, operator[] shouldn't do any checking; only the at() method should throw an exception if an invalid index is specified.

  4. #19
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    Even then, the extra bounds checking that at() does might be worth it. In many cases any performance differences are not noticeable. However, the benefits of using the safer option are real (as this example already shows).

  5. #20
    Algorithm Dissector iMalc's Avatar
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    It seems so far that we're all just assuming that we know the answer to the below question:
    xyz_size isn't a constant known at compile time is it?
    Not meaning to insult anyone of course.
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  6. #21
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    xyz_size is not known ahead of time.

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