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Re: [Mingw-users] msvcrt printf bug




And btw: when will YOU become "humble" and start to "study more"? ;-)

On 18-Jan-17 03:44, Emanuel Falkenauer wrote:
> 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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