Re: int(x) is .ne. to x when x is whole number.

["H.S.Rai" <hsraidce@xxxxxxxxxxxxxxxxxxxx>]

Dear Shridhar

Thanks for your good reply. Sir, I am fully aware that 1/3.0 * 3 is not
equal to one, and my program is not involving such or other trignometric
calculations. It is simply adding 0.2 to intial number 0.0 a number of
times. I want to know root couse of problem as I assume such behaviour
shhould not be there.

I thing you help by providing pointer or answer to this.

Bye
h s rai
rurki ( uttaranchal )



*************************************************************************

On Tue, 28 Nov 2000, Shridhar Daithankar wrote:

> Hi
> 
> It looks that the routine generating the float is not producing exact numbers.
> It's very possible if you are using some trigometric series type stuff to
> generate it. These are precision errors and usually can be avoided.
> 
> 1)How to generate error. e.g do PI/4-atan(tan(PI/4)). See it's not zero... :-))
> 2)How to rectify the error? Define some epsilon like 1e-6, say. and trip it to
> that precision.
> 
> x=atof(sprintf(str,"%6.4f",x));
> 
> So you got it.
> 
> Check out the syntax. I am not sure. It's been long time I touched maths.
> 
> HTH
> 
>  Bye
>    Shridhar
> 
> P.S. This has nothing to do with linux. Anyway you need to understand how does
> computer computes. That will tell you such problems in advance... :-))
> 
> "H.S.Rai" wrote:
> 
> > All linux Programmers,
> >
> >         I have written a program in which I have to check variable, and
> > in case it is whole number, follow some different path. To check this,
> > float variable is casted with int, and if difference of int(x) and x is
> > zero, it should be a whole number. For posting purpose I simplified
> > program just to highlight the problem. The differnece is zero only for ist
> > two execution of loop, after that it is not zero, which make my flow of
> > program wrong. At the end, output ( line ended with '****' mean unexpected
> > results), and source code of program is appended.
> >
> > Pl help me by pointing out my mistake, and suggest how to implement such a
> > logic. I am using g++ on REDHAT 6.2 (kernel 2.2.14-5.0 ).
> > ______________________________________________________________
> >
> > Result File:
> >
> > Integer Float   Differance
> > 0       0       0
> > 0       0.2     0.2
> > 0       0.4     0.4
> > 0       0.6     0.6
> > 0       0.8     0.8
> > 1       1       0
> > 1       1.2     0.2
> > 1       1.4     0.4
> > 1       1.6     0.6
> > 1       1.8     0.8
> > 2       2       2.38419e-07             **** / 3rd coloumn should be 0 /
> > 2.2     0.2
> > 2       2.4     0.4
> > 2       2.6     0.6
> > 2       2.8     0.8
> > 3       3       4.76837e-07             **** /     do                /
> > 3       3.2     0.200001                **** / 3rd coloumn should be .2/
> > 3       3.4     0.400001                ****
> > 3       3.6     0.600001                ****
> > 3       3.8     0.800001                ****
> > 4       4       4.76837e-07             ****
> > 4       4.2     0.2
> > 4       4.4     0.4
> > 4       4.6     0.6
> > 4       4.8     0.8
> > 4       5       1
> 
> 
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