---------------- 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 have entered the problem into the bug database for GNU Classpath; see http://savannah.gnu.org/bugs/index.php?func=detailitem&item_id=7123 Thanks a lot for your help, -- Sascha Sascha Brawer, [EMAIL PROTECTED], http://www.dandelis.ch/people/brawer/ Index: poly/test.c =================================================================== RCS file: /cvs/gsl/gsl/poly/test.c,v retrieving revision 1.16 diff -u -r1.16 test.c --- poly/test.c 26 Jul 2003 13:44:36 -0000 1.16 +++ poly/test.c 7 Jan 2004 13:32:21 -0000 @@ -102,6 +102,18 @@ gsl_test_rel (x1, 2.0, 1e-9, "x1, 5 x^2 = 20"); } + { + /* From the Mauve test suite, used by GNU Classpath. */ + double x0, x1; + + int n = gsl_poly_solve_quadratic (0.1, 20.0, 1000.0, &x0, &x1); + + gsl_test (n != 1, + "gsl_poly_solve_quadratic, (x^2)/10 + 20x + 1000 = 0"); + gsl_test_rel (x0, -100.0, 1e-9, "x0, (x^2)/10 + 20x + 1000 = 0"); + } + + /* Cubic */ { ----------------- End Forwarded Message ----------------- _______________________________________________ Classpath mailing list [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/classpath
