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From: | Waldemar Schultz <schultz AT ma DOT tum DOT de> |
Newsgroups: | comp.os.msdos.djgpp |
Subject: | Re: Floating point exception |
Date: | Tue, 04 Jul 2000 15:33:52 +0200 |
Organization: | [posted via] Leibniz-Rechenzentrum, Muenchen (Germany) |
Lines: | 42 |
Message-ID: | <3961E7C0.178AC0B6@ma.tum.de> |
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Eli Zaretskii schrieb: > > Isn't it better to link against libm.a and write a custom version of > `matherr'? See "info libc alpha matherr" for more information. matherr usage of course works fine with math FUNCTIONS. > > The second problem is: is it possible to throw an exception when a number > > becomes NaN (NOTaNUMBER) ir Inf (Infinite) ? > > You will have to give more details about how exactly do these come > into existence. Does it happen in an FP instruction such as division > or multiplication? Does it happen in a function? The answer depends > on these details. if I don't use FPE double a=0; double b=1; double c=b/a; double d=a*c; printf("%g %g\n",c,d); just prints 'Inf NaN', so if I don't have the printf, I wouldn't be notified by matherr of course. Because of the huge amount of math operations in the whole program it isn't feaseable to add something like 'if(fabs(a)<EPS) ...' ir 'if(!finite(c)) ...' before any aritmetic operation. so forehand I think I will use a combination of both and try to avoid an environment where FPE is supposed to crash. Or anyone a still better idea? BTW: is it FPE or raise(SIGABRT) which causes the problems? so if it were raise(SIGABRT) I would be fine if I could do somthing like print_symified_traceback(...); // anyone did that before ??? exit(1); instead. Many thanks for your immediate help -- Gruss Waldemar Schultz. Technische Universität München, Zentrum Mathematik M1, D 80290 München Tel: +49 (0)89 2892 8226 FAX: +49 (0)89 2892 8228
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