From:	"A. Sinan Unur" <sinan DOT unur AT cornell DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Round off errors
Date:	Fri, 20 Feb 1998 10:50:40 -0600
Organization:	Cornell University
Lines:	41
Sender:	asu1 AT cornell DOT edu (Verified)
Message-ID:	<34EDB460.1AC6@cornell.edu>
References:	<01bd3e0c$200881c0$LocalHost AT alfredoc>
Reply-To:	sinan DOT unur AT cornell DOT edu
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Alfredo J. Cole wrote:
> 
> Compiling the following code with DJGPP gives the erroneous result
> (5551.20). The same code compiled with Borland's bcd class gives the
> correct result (5551.22). I am developing an accounting system with
> DJGPP and it requires that the results be exact. Is there a similar
> class or option under DJGPP that will eliminate these round off
> errors?

round off errors are a fact of life if you are using floating point
arithmetic. your best bet is not to use floating point arithmetic for
accounting software. note that this is _not_ at all a djgpp specific
problem. basic floating point. if you want to see another example, try

C:\TEMP>type fp.c
#include <stdio.h>

int main(void)
{
 int i;
 float g, data[3] = { 1, -10e9, 10e9};

 for(g=0.0, i=0; i<3; i++)
   g += data[i];

 printf("%g\n",g);

 for(g=0.0, i=0; i<3; i++)
   g += data[2-i];

 printf("%g\n",g);

 return 0;
}

C:\TEMP>fp
0
1


  -- Sinan

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