RE: Strange behavior

["Robert Collins" <robert.collins@itdomain.com.au>]

Floating point comparisons should _always_ be done via a confidence
interval, not bitwise equality. As for determinism, I don't know what
the logic circuits look like, so can't and won't comment :}.

Rob



> -----Original Message-----
> From: Chuck Allison [mailto:cda@freshsources.com] 
> Sent: Monday, March 04, 2002 4:08 PM
> To: Richard R. Malloy; Randall R Schulz
> Cc: Ross Smith; cygwin@cygwin.com
> Subject: Re: Strange behavior
> 
> 
> That's the point. They're always redued, so in both cases, 
> the expression 2.0/3.0 is evaluated. How can that be 
> non-deterministic?
> 
> ----- Original Message -----
> From: "Richard R. Malloy" <rrmalloy@attbi.com>
> To: "Randall R Schulz" <rrschulz@cris.com>
> Cc: "Ross Smith" <rosss@pharos.co.nz>; "'Chuck Allison'" 
> <cda@freshsources.com>; <cygwin@cygwin.com>
> Sent: Sunday, March 03, 2002 9:47 PM
> Subject: Re: Strange behavior
> 
> 
> > OK. I'm no IA32 expert can someone explain the following 
> results.  (Do 
> > the floating point registers use guard bits, randomly initialized 
> > perhaps?)
> >
> > bool operator==(const Rational& r1, const Rational& r2)
> > {
> >   double a=r1.toDouble(), b=r2.toDouble();
> >   cout << ?== a " << a << " " << ?== b " << b << endl;
> >   return a == b;
> >   //  return r1.toDouble() == r2.toDouble();
> >   /*  return ( r1.numerator == r2.numerator && r1.denominator == 
> > r2.denominator ); */ }

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Bug reporting:         http://cygwin.com/bugs.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/