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Thread: Same program same data different result

  1. Jul 3rd, 2008, 09:48 AM #1
    King Arthur
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    Same program same data different result

    Hi, I don't know if this is the right place for this post. No doubt it will be moved if it isn't....

    I recently wrote a program which involved a lot of number crunching (thousands of operations) - but NO random numbers...

    On an machine running XP I get one answer - on a machine running Vista I get a slightly different answer.

    Anyone any ideas? Is there a difference between Vista and XP in the way they deal with numbers?

    Thanks.
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  2. Jul 3rd, 2008, 11:09 AM #2
    NickThissen
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    Re: Same program same data different result

    You could start by showing some of your code? We can't guess what kind of operations you are talking about, can we?
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  3. Jul 3rd, 2008, 12:06 PM #3
    Dnereb
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    Re: Same program same data different result

    Do you use Doubles and .... is the Vista 64 bits?
    Would explain a lot.
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  4. Jul 3rd, 2008, 03:00 PM #4
    King Arthur
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    Re: Same program same data different result

    There isn't anything fancy in the operations - just the four rules of number. There is far to much code to start quoting it... It is a big program....

    The Vista laptop is 32 bit. I don't use doubles in the part of the program that causes the small differences.

    I just wondered if there was anything obvious in the way Vista worked that could account for it...
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  6. Jul 3rd, 2008, 06:53 PM #5
    VBAhack
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    Re: Same program same data different result

    Perhaps a stupid question, but if you ran it 10 times on the same machine, do you get the exact same answer every time?
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    (Links: Cubic Spline Tutorial, Parametric Cubic Spline Tutorial, VB Numerical Routines    )

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  7. Jul 5th, 2008, 01:33 AM #6
    MaximilianMayrhofer
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    Re: Same program same data different result

    Without a doubt, the difference is caused by the way the two operating systems handle numbers. How, exactly, though i'm not sure.
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  8. Jul 5th, 2008, 02:13 AM #7
    Dnereb
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    Re: Same program same data different result

    Still thinking it's about doubles or singles
    probably some inexplicit conversion to a double like

    Dim A as Long
    A = tolng(34 + (71/3) *( 5/6))

    Or
    Dim A as Variant
    A = 9872442/957
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  9. Jul 18th, 2008, 07:24 PM #8
    Code Doc
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    Re: Same program same data different result

    Quote Originally Posted by King Arthur
    There isn't anything fancy in the operations - just the four rules of number. There is far to much code to start quoting it... It is a big program....

    The Vista laptop is 32 bit. I don't use doubles in the part of the program that causes the small differences.

    I just wondered if there was anything obvious in the way Vista worked that could account for it...
    Vista has nothing to do with it. The computer hardware that uses the operating system might have something to do with it.
    Doctor Ed
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  11. Jul 19th, 2008, 12:53 AM #9
    King Arthur
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    Smile Re: Same program same data different result

    Thanks a lot Code Doc. I wouldn't want to blame Vista if the problem might lie elsewhere.... anyway - it is something I can 'live with'.
    Regards
    King Arthur
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