Re: precision problem with mex file

[fredounet]

thanks, it helped me a lot.

e 18/07/2013 09:45, CdeMills [via Octave] a écrit :
>
>     fredounet wrote
>     
> A=351.40999999999985448084771633148193359375000000000000*351.40999999999985448084771633148193359375000000000000;
>
>     
> A=A+105.45999999999912688508629798889160156250000000000000*105.45999999999912688508629798889160156250000000000000;
>
>
> This does not make sense. Octave uses IEEE-754 double precision
> numbers, which means 53 bits of mantissa, and around 16 decimal
> digits. Your numbers seems to have 40 significant digits, this is not
> supported at the present time. "Things are working" means that you can
> not detect truncation effects. Do not forget that numbers like 351.41
> are NOT exact, finite-length in binary representation. I mean that you
> require an infinite sequence of digits to approximate it in base ten;
> 0.410156250 is an exact number in base two.
>
> If you really want to work at that level of accuracy, I'm porting a
> package called mptoolbox; have a look at
> hg.code.sf.net/p/octave/multi-precision for a sort-of working version.
>
> Regards
>
> Pascal
>
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