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

[Shridhar Daithankar <shridhar_daithankar@xxxxxxxxxx>]

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