Is there a standard function?

This is a discussion on Is there a standard function? within the C Programming forums, part of the General Programming Boards category; Originally Posted by phantomotap O_o I'm sorry for the confusion. I did not post any source. I only posted that ...

  1. #196
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    Quote Originally Posted by phantomotap View Post
    O_o

    I'm sorry for the confusion. I did not post any source.

    I only posted that comment to playfully mock the other posters.

    *shrug*

    Anyway. What can you really expect from a 1800 MiB array loosely indexed by repeatedly dividing `double' values?

    Soma
    Actually I didn't have time enough to check all the posts,
    I've been quite busy lately.
    I didn't even see somebody was trying to buid a mega-array. :-)
    Or I just skipped it thinking it was too much to handle.

    Thanks anyway for your comments, no matter what.

  2. #197
    Registered User whiteflags's Avatar
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    Quote Originally Posted by frktons View Post
    Hi whiteflags.

    I tried your code, but it displays million lines on the screen,
    so it is not something I can test for performance. :-(

    What should this test program shows? Remember I'm a beginner
    and many things are obviously unknown to me.

    I can analyse your code with my eyes, not with a profiler for the time
    being, and get some insight/inspiration from it. But if you think it is
    worth to try for performance, please post a suitable version.

    Thanks
    A profiler runs in the background as another program.

    The output is just everyone's formatting of a string of random numbers. It's not important.

    I arranged a test on my computer for a few versions we've seen in this thread, and posted the results in the headtohead.txt file (the very post you replied to). If you just wanted to know which one is the fastest of them all, then anyone could run a profile and tell you. So I did. I posted the code so people understood what I profiled. Then they could argue about the results, except, spoiler: nobody cares.

    The fact that I did this test on my computer and not yours -- that I have no idea what kind of profile you really need -- is exactly why information like what CPU architecture I have; what compiler, version, and build options I used are important. After all, if you want to format integers on a CRAY supercomputer, my podunk system means nothing to you.

    Though, I can guess you're not after anything like that. TBH, this is getting quite out of hand and silly. There are plenty of people in computer science who think they care about performance. They care (emotionally) about wasted milliseconds. When I posted my recursive version, everyone took a big performance ........ all over it.

    Don't get me wrong, they were correct . It still only took about 300 milliseconds to format the average integer. In private tests, Adak's method was only about 20 milliseconds faster. If you are in such dire straights that you need that improvement, fine, but I do not think you have the foundation to be making such judgments. You should not be worrying about it. There should not be a great difference between competent, correct versions in terms of speed.

    Think about performance on a case by case basis for now. You have some idea how patient I was, waiting for one million formats to occur and be displayed. You are most likely not going to be using it like that.
    Last edited by whiteflags; 07-07-2010 at 01:28 PM.

  3. #198
    Algorithm Dissector iMalc's Avatar
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    Absolutely. And let me also hilight that correctness is far more important than speed. The first version I posted, using sprintf is absoultely far preferable to my later versions because it was quick and easy to write, easy to read, and clearly correct.
    Something like the last version I wrote is the kind of thing that should only be the domain of library writers. I.e. I wouldn't be surprised if when taking out the lines that add commas, that it gives Microsoft's itoa a run for its money.
    The typical programmer shouldn't have to deal with this kind of thing though.

    Elysia and Adak, I think the rest of us are past caring about whatever the disagreement is, and you know each other's position. There is nothing more to be said.
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    Quote Originally Posted by frktons View Post
    @cyberfish:

    if you can help me solve these compiling errors of your code
    I can try it on my testpad:
    Code:
     error #2048: Undeclared identifier 'BUF_LEN'.
     Missing prototype for 'memmove'.
    *** Error code: 1 ***
    Done.
    Code:
    #define BUF_LEN 15
    or whatever the length of your buffer is.

    memmove needs
    #include <string.h>

  5. #200
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by iMalc View Post
    Elysia and Adak, I think the rest of us are past caring about whatever the disagreement is, and you know each other's position. There is nothing more to be said.
    I was going to ask a moderator to delete those posts once we have reached a settlement.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Actually your test is about 5 times faster than the one I used last.
    It is however faster than assembly tests somebody did, so it is quite
    improbable that it is just the better compiler, something else should be
    the reason.
    The algorithm is usually much more important than whether it's coded in C or assembly.

    A quicksort written in C compiled by a lousy compiler will still be orders of magnitude faster than a bubble sort coded in optimal assembly, on large arrays.

    Even when it's the same algorithm, unless you have extensive experience in assembly and VERY good understanding of the hardware you are working on (how many cycles each instructions take, what instructions can be executed in parallel, what's the cost of branch misprediction etc), you probably still won't beat a modern optimizing compiler.

    Modern compilers are just way too smart. And they have all the extensive hardware knowledge coded in.

    Usually the best optimization is to keep your code as simple as possible (but with a fast algorithm), so the compiler can optimize better.

  7. #202
    Registered User whiteflags's Avatar
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    Quote Originally Posted by Elysia View Post
    I was going to ask a moderator to delete those posts once we have reached a settlement.
    So you can have the argument again at a later time when you've conveniently forgotten everything you said?

  8. #203
    Algorithm Dissector iMalc's Avatar
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    I take it back. My last version was a waste of time. Compilers already perform the same optimisation trick, except that they are able to do it using the high 32-bit part of a 64 bit result from multiplication of two 32-bit numbers. This means that they can do the same tricks themselves, but more efficiently.
    See here: ridiculous_fish Blog Archive Labor of Division (Episode 1)
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  9. #204
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by whiteflags View Post
    So you can have the argument again at a later time when you've conveniently forgotten everything you said?
    Forget that Adak uses Turbo C? That's unlikely to happen...
    Either it's deletion time or it's moving time. But putting all this in a special thread?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  10. #205
    Registered User whiteflags's Avatar
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    Why don't you just leave things alone and appreciate this thread with all its warts. Maybe if you leave things alone, you will remember how ugly this thread was. If we let you delete history, you both will never learn from it.

  11. #206
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    Quote Originally Posted by Elysia
    Either it's deletion time or it's moving time. But putting all this in a special thread?
    Tough, because you guys mix the on-topic stuff with the off-topic stuff. Just live with it.
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  12. #207
    Master Apprentice phantomotap's Avatar
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    I take it back. My last version was a waste of time.
    o_O

    Bummer.

    Soma

  13. #208
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    Quote Originally Posted by laserlight View Post
    Tough, because you guys mix the on-topic stuff with the off-topic stuff. Just live with it.
    Quote Originally Posted by Elysia View Post
    Forget that Adak uses Turbo C? That's unlikely to happen...
    Either it's deletion time or it's moving time. But putting all this in a special thread?
    To clarify that, I was going to ask to either delete the posts or move them. Ask if the keyword.
    And initially, I was going to ask not because it looks bad to me, but because it looks bad to everyone else (like hijacking).
    Anyway, the moderators judgment is final.

    Besides, it is also possible to edit the non-topic stuff.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Quote Originally Posted by cyberfish View Post
    Code:
    #define BUF_LEN 15
    or whatever the length of your buffer is.

    memmove needs
    #include <string.h>
    Thanks.

    Now it compiles, but the output is weird:
    Code:
                             Testing version : 0.60
    
                             ----------------------
    
     The value of num is: -1234567890
    
     The formatted value of num is: ☼
     Elapsed ClickTime: 1,420
     to perform 10,000,000 cycles of the formatting function
    Maybe I forgot something else.
    Attached the whole source for your convenience. :-)
    Attached Files Attached Files

  15. #210
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    Quote Originally Posted by iMalc View Post
    I take it back. My last version was a waste of time. Compilers already perform the same optimisation trick, except that they are able to do it using the high 32-bit part of a 64 bit result from multiplication of two 32-bit numbers. This means that they can do the same tricks themselves, but more efficiently.
    See here: ridiculous_fish Blog Archive Labor of Division (Episode 1)
    Well, Malcom your code wasn't a waste of time at all.
    You had a very nice idea and coded it with standard C, with
    outstanding performance.

    Even if some compiler is able to do that, it doesn't mean that
    your effort if worthless.

    I have appreciated it very much. And I'm going to study it as well
    time and knowledge permitting.
    :-)

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