Sascha Brawer writes: > ---------------- Begin Forwarded Message ---------------- > Subject: Re: Quadratic and cubic equations > Date Sent: Wednesday, January 7, 2004 3:17 PM > From: Sascha Brawer <[EMAIL PROTECTED]> > To: Brian Gough <[EMAIL PROTECTED]> > CC: Mark Wielaard <[EMAIL PROTECTED]>, Michael Koch <[EMAIL PROTECTED]> > > Hi Brian > > we have a problem with solving a specific quadratic equation in GNU > Classpath. For your convenience, I've re-written the problematic equation > as a patch to the GSL test suite (gsl/poly/test.c); see below. > > I suspect that the problem is the test for (disc == 0) in gsl/poly/ > solve_quadratic.c, line 61. With the Java version of your code, we get a > very small negative number in gcj (the Java front-end for the GCC) on IA- > 32, and exactly 0.0 with some other Java Virtual Machines. > > Could it be that the test for (disc == 0) should actually be replaced by > something like (fabs(disc - 0.0) < EPSILON)? If so, which value is > appropriate for EPSILON?
I don't think so, no. The problem is that 0.1 cannot be represented exactly, so it's a matter of whether the discriminant ends up being a very small positive number, a small negative number, or zero. solveQuadratic isn't wrong: its argument is. It looks to me like this is a test of exact java strictfp compliance. gcj fails, because it isn't strictfp compliant. Andrew. _______________________________________________ Classpath mailing list [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/classpath
