🚀 go-pugleaf

In article <1993Nov24.155323.22771@njitgw.njit.edu>,
Ken Nakata <kxn3796@hertz.njit.edu> wrote:
>I wrote a program for my VAX assembly class' programming assignment
>and it solves simple equations by iteration.  C version is following;
>-------------------------------------------------------------------------------
>#include <stdio.h>
>#include <math.h>
>
>main()
>{
>  double x = 1.0, px;
>  double y = 2.0, py;
>
>  do {
>    px = x;
>    py = y;
>    x = 1.0 + sqrt(px * px + py * py) / 10.0 * cos(py);
>    y = 2.0 + (sin(px) + sin(py) - px) / 20.0;
>  } while (abs((x - px) / x) > 1.0e-16 ||
>	   abs((y - py) / y) > 1.0e-16);
>  printf("x = %17.15lf\ny = %17.15lf\n", x, y);
>}
>-------------------------------------------------------------------------------
>My VAX assembly program agrees with the above C program compiled by cc
>on SunOS 4.x.x (sorry don't remember);
>
>x = 0.899475740409558
>y = 2.038799794467183
>
>However, the same C program compiled by two versions of gcc (2.4.3 and
>2.3.1) don't agree with the above results;
>
>x = 0.906946738485910
>y = 2.037538420581679
>
>Gcc 2.4.3 is running on a DECstation/Ultrix and 2.3.1 is running on
>Sun Sparc/SunOS 4.x.x (Same program compiled by cc on Ultrix doesn't
>get result in reasonable amount of time).
>
>Emacs Calc running on Emacs 18.59 also agrees with my VAX assembly
>program (I fed two results to the equations to see if same results
>come up).
>
>Why?  Is this a bug of gcc?
>Thanks in advance.
>
>Ken Nakata

 Try changing abs() to fabs()

 ... gcc 2.5.4 gives exactly same results as Your VAX cc. 

 /jjp

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	Jyri Pekkanen  :  Jyri.Pekkanen@hut.fi  :  +358-0-513-169
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