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Re: [Mingw-users] msvcrt printf bug




Hi KHMan,

Sorry, but you're WRONG: Tei's code is actually INVALUABLE to us (and 
certainly not "Yawn"!!) - you'd be better off not berating him (or her?) 
to be "a student" (why would "a student" be worse than you, btw?!) and 
THINK about what (s)he has to say before making clearly wrong conclusions!

Emanuel

On 18-Jan-17 03:20, KHMan wrote:
> On 1/18/2017 6:27 AM, tei.andu@xxxxxxxxxxxx wrote:
>> Hello all,
>> Thank you for your kind advice and your time. I also did some more
>> searching around.
>> I understand that there is no practicality to getting the exact
>> value of a float, only enough precision
>> that can give a back conversion (decimal string -> float) with the
>> same value is required.
>> However, my examples are correct. You can verify them with a
>> calculator with enough precision or a bignum library (or glibc).
>> If you google 'exact value of a float' you will even find code
>> samples that will do that. glibc also does it. The digits are not
>> garbage, they are the result of a complete conversion.
> [snip snip]
>
> Ultimately, you bear the risks. If you are still a student, be
> humble, study more. Think before you cry wolf.
>
>> http://stackoverflow.com/questions/3215235/how-do-you-print-the-exact-value-of-a-floating-point-number
>> There is no rounding required if we want this exact value, no
>> floating point operations required,
> [snip snip]
>
> The blog post states there were ZERO errors doing round trips. No
> errors. What bug?
>
> Google may have smart people laser focused on the wrong things
> too. Do not trust too easily.
>
> So he wants to find perfection in ASCII displays of floats.
> Yawn... Google and Google employees have money, leave them to play...
>
> Once you do calculations in floating point, whatever 0.5ULP does
> not matter anymore, error accumulates, the perfect ASCII display
> is an exercise in perfectionism. Go and have fun with the
> so-called perfect conversion code, however dubious its real-world
> value is, but it's foolish to tell the world there are bugs here
> and there. Think before you act, man.
>
> IIRC you should not consider your kind of perfect ASCII conversion
> to be of any real importance in real world settings. There was
> once an article -- a grad student doing aerospace, his program was
> so sensitive to tiny pertubations that he only got useful *cough*
> 'results' on a particular CPU. Other CPUs gave wildly different
> results. After graduating, he questioned whether the program which
> was supposed to produce consistently reproducible results was
> actually useful if it amplified tiny variations in calculations
> and made a molehill out of them. Was his research results good
> valuable simulation or a molehill? Hmmm...
>
> Error accumulates in real world calculations. Folks who enjoy
> their perfect ASCII conversions should remain in their niche.
>
> [snip snip]
>


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