>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
confidence intervals are indeed the only way... but as to determinism ... its a function of your compiler I believe. Differences will likely arrise with or without optimisation. Which coincidently - is also the difference between the 2 situations below, 1 is an optimisation of the other, the assembly produced, even without an optimisation flag, will be different, which means different results (one case needs temporary variables - other one does not). So it should be deterministic for a single set of assembly, for a given system type... although someone could easily of made a processor in which I am wrong. Gareth > > > > > -----Original Message----- > > From: Chuck Allison [mailto:[EMAIL PROTECTED]] > > Sent: Monday, March 04, 2002 4:08 PM > > To: Richard R. Malloy; Randall R Schulz > > Cc: Ross Smith; [EMAIL PROTECTED] > > 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" <[EMAIL PROTECTED]> > > To: "Randall R Schulz" <[EMAIL PROTECTED]> > > Cc: "Ross Smith" <[EMAIL PROTECTED]>; "'Chuck Allison'" > > <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> > > 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/ > _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.; -- 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/
