Date: Fri, 19 Sep 1997 11:47:04 +0200 From: Christoph Kukulies <kuku@gilberto.physik.RWTH-Aachen.DE> To: Terry Lambert <tlambert@primenet.com> Cc: Christoph Kukulies <kuku@gilberto.physik.RWTH-Aachen.DE>, freebsd-hackers@freefall.FreeBSD.org Subject: Re: FPE problem Message-ID: <19970919114704.51622@gil.physik.rwth-aachen.de> In-Reply-To: <199709181618.JAA17494@usr03.primenet.com>; from Terry Lambert on Thu, Sep 18, 1997 at 04:18:06PM %2B0000 References: <19970918163531.11717@gil.physik.rwth-aachen.de> <199709181618.JAA17494@usr03.primenet.com>
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On Thu, Sep 18, 1997 at 04:18:06PM +0000, Terry Lambert wrote: > > A little bit more info now: > > > > ret_val = -z__ * (spint_1.a1 * z__ * (spint_1.a2 * z__ * (spint_1.a3 * > > z2 * (spint_1.a4 * z2 * (spint_1.a5 * z2 * (spint_1.a6 * z2 * > > (spint_1.a7 * z2 * (spint_1.a8 * z2 * (spint_1.a9 * z2 * ( > > spint_1.a10 * z2 + 1.) + 1.) + 1.) + 1.) + 1.) + 1.) + 1.) + > > 1.) + 1.) + 1.) + spint_1.zeta2 + z__ * log(1. - *x); > > > > > > (xxgdb) info float > > u: status 0x82e1: exceptions: INVALID LOS FPSTACK; flags: 0010; top 0 > > e: status 0x200: flags: 0010; top 0 > > control 0x1272: compute to 53 bits; round NEAREST; mask: DENORM UNDERF LOS; > > last instruction: opcode 0x1d0; pc 0x8:0xf01f9a96; operand 0x27:0x92844 > > [ ... ] > > > What is LOS ? Loss of significance? > [ valuable floating point insights ommitted ] Now it's getting funny: The exception only occurs on certain machines. I have a dynamically linked binary which I compiled on an around July -current 486 machine and it does *not* do a FPE there. The machines where it occurs were built with CFLAGS= -ffast-math -m486 -O2 That means that libm (or libmsun) were built with inline fpu instructions and this is causing the trouble. I will rebuild the math libs with conservative switches now. > > If it's any consolation, I was stumped for a good week the first > time this happened to me. That's about 1.0e13 Proton-Proton pair > production collisions on the very expensive hardware I was using. 8-(. > > > Regards, > Terry Lambert > terry@lambert.org > --- > Any opinions in this posting are my own and not those of my present > or previous employers. -- --Chris Christoph P. U. Kukulies kuku@gil.physik.rwth-aachen.de
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