Re: floating point exceptions
In [EMAIL PROTECTED], Nate Lawson wrote: I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the httperf-0.6 port gives a SIGFPE and dumps core when run against a system that has no web server running. (The default behavior is to measure localhost when no arguments are specified). It seems this is caused by a divide by zero error since the delta between connections ends up being zero. The author suggest that the divide should return a defined value, Inf, according to the IEEE floating point standard. FreeBSD generates SIGFPE. I temporarily patched the code locally to check for a delta of zero and arbitrarily set it to 1.0 so that the divide succeeds and everything comes out ok without crashing. FreeBSD up to 3.x defaults to have exceptions unmasked. This was changed before 4.0 and should be in 4.x/4-STABLE and in 5-current. Are you sure you get this on a real 4.0 system, not one from a few weeks before release? If so, what is the version of /usr/include/machine/npx.h? It should be 1.18. Of course, the kernel should be complied with it in case this is a source-updated system. Anyway, the solution is fpsetmask, as others noted. Also note that FreeBSD/gcc/ANSI C 89 have a few other problems with IEEE 754 compatibility so that we can't claim conformity in any case. Please check the mail archives on www.freebsd.org, this has been discussed every 7 months for the last 5 years now. Martin -- % Martin Cracauer [EMAIL PROTECTED] http://www.cons.org/cracauer/ BSD User Group Hamburg, Germany http://www.bsdhh.org/ To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
On Fri, 5 May 2000, Martin Cracauer wrote: In [EMAIL PROTECTED], Nate Lawson wrote: I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the httperf-0.6 port gives a SIGFPE and dumps core when run against a system that has no web server running. (The default behavior is to measure localhost when no arguments are specified). It seems this is caused by a divide by zero error since the delta between connections ends up being zero. The author suggest that the divide should return a defined value, Inf, according to the IEEE floating point standard. FreeBSD generates SIGFPE. I temporarily patched the code locally to check for a delta of zero and arbitrarily set it to 1.0 so that the divide succeeds and everything comes out ok without crashing. FreeBSD up to 3.x defaults to have exceptions unmasked. This was changed before 4.0 and should be in 4.x/4-STABLE and in 5-current. Are you sure you get this on a real 4.0 system, not one from a few weeks before release? If so, what is the version of /usr/include/machine/npx.h? It should be 1.18. Of course, the kernel should be complied with it in case this is a source-updated system. Anyway, the solution is fpsetmask, as others noted. Also note that FreeBSD/gcc/ANSI C 89 have a few other problems with IEEE 754 compatibility so that we can't claim conformity in any case. Please check the mail archives on www.freebsd.org, this has been discussed every 7 months for the last 5 years now. Thanks for the information. I checked the system again and it is indeed 4.0-2127-CURRENT (ie. just before 4.0-RELEASE). I will upgrade. David, is it possible to add the following to the httperf port? #ifdef __FreeBSD__ fpsetmask(~FP_X_DZ); #endif Thanks, Nate To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
On Wed, Apr 26, 2000 at 11:03:45AM -0500, Dan Nelson wrote: In the last episode (Apr 26), Sheldon Hearn said: On Tue, 25 Apr 2000 00:05:23 MST, Brooks Davis wrote: Is FreeBSD's behavior correct? Why or why not? You can use the included code snippet to verify that this occurs. FreeBSD has traditionaly violated the IEEE FP standard in this regard. This is fixed in 5.0 and I think in 4.0-STABLE (though I can't remember what file this is in so I can't check.) Huh? I'm pretty sure you've got this backwards. FreeBSD has traditionally upheld the standard and we only recently decided to go with the flow in 5.0. No; we held our moral ground against IEEE, until 5.0 when we gave in. The IEEE standard says "trap nothing". For most programs, this is the wrong thing to do, since they are not signal-processing apps or numerical analysis programs and a divide by zero is a coding error. I'd rather have my program die on an unexpected divide by zero than continue with invalid data. Why should we treat (1.0/0.0) any differently from (1/0)? Because 0.0 might be the closest approximation to whatever number you were really trying to divide by that the hardware can manage. 0 is never an approximation to 1 or -1. Dividing is for wimps, anyway.:-) -- Andrew To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
Wilko Bulte wrote: On Wed, Apr 26, 2000 at 12:16:51PM -0400, Bill Fumerola wrote: On Wed, Apr 26, 2000 at 11:03:45AM -0500, Dan Nelson wrote: Why should we treat (1.0/0.0) any differently from (1/0)? Because Linux has the uncanny ability to both divide by zero and produce the shittiest coders the world has ever seen. Which brings me to the inevitable question: 'can NT divide by zero' ? ;-) No, at least not in US Navy installations. It also cannot recover from divide by zero errors, leading a brand new US warship to be towed in from sea trials. The NT-powered nuclear navy. Be afraid. Be very afraid. -- "Where am I, and what am I doing in this handbasket?" Wes Peters Softweyr LLC [EMAIL PROTECTED] http://softweyr.com/ To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
On Tue, 25 Apr 2000 00:05:23 MST, Brooks Davis wrote: Is FreeBSD's behavior correct? Why or why not? You can use the included code snippet to verify that this occurs. FreeBSD has traditionaly violated the IEEE FP standard in this regard. This is fixed in 5.0 and I think in 4.0-STABLE (though I can't remember what file this is in so I can't check.) Huh? I'm pretty sure you've got this backwards. FreeBSD has traditionally upheld the standard and we only recently decided to go with the flow in 5.0. Ciao, Sheldon. To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
In the last episode (Apr 26), Sheldon Hearn said: On Tue, 25 Apr 2000 00:05:23 MST, Brooks Davis wrote: Is FreeBSD's behavior correct? Why or why not? You can use the included code snippet to verify that this occurs. FreeBSD has traditionaly violated the IEEE FP standard in this regard. This is fixed in 5.0 and I think in 4.0-STABLE (though I can't remember what file this is in so I can't check.) Huh? I'm pretty sure you've got this backwards. FreeBSD has traditionally upheld the standard and we only recently decided to go with the flow in 5.0. No; we held our moral ground against IEEE, until 5.0 when we gave in. The IEEE standard says "trap nothing". For most programs, this is the wrong thing to do, since they are not signal-processing apps or numerical analysis programs and a divide by zero is a coding error. I'd rather have my program die on an unexpected divide by zero than continue with invalid data. Why should we treat (1.0/0.0) any differently from (1/0)? -- Dan Nelson [EMAIL PROTECTED] To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
On Wed, Apr 26, 2000 at 11:03:45AM -0500, Dan Nelson wrote: Why should we treat (1.0/0.0) any differently from (1/0)? Because Linux has the uncanny ability to both divide by zero and produce the shittiest coders the world has ever seen. -- Bill Fumerola - Network Architect Computer Horizons Corp - CVM e-mail: [EMAIL PROTECTED] / [EMAIL PROTECTED] Office: 800-252-2421 x128 / Cell: 248-761-7272 To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
On Wed, Apr 26, 2000 at 12:16:51PM -0400, Bill Fumerola wrote: On Wed, Apr 26, 2000 at 11:03:45AM -0500, Dan Nelson wrote: Why should we treat (1.0/0.0) any differently from (1/0)? Because Linux has the uncanny ability to both divide by zero and produce the shittiest coders the world has ever seen. Which brings me to the inevitable question: 'can NT divide by zero' ? ;-) -- Wilko Bulte Powered by FreeBSD http://www.freebsd.org http://www.tcja.nl To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
In the last episode (Apr 27), Andrew Reilly said: Because 0.0 might be the closest approximation to whatever number you were really trying to divide by that the hardware can manage. 0 is never an approximation to 1 or -1. Aaah, but that assumes you're not also trapping on underflow :) -- Dan Nelson [EMAIL PROTECTED] To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: floating point exceptions
I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the
httperf-0.6 port gives a SIGFPE and dumps core when run against a system
that has no web server running. (The default behavior is to measure
localhost when no arguments are specified).
It seems this is caused by a divide by zero error since the delta between
connections ends up being zero. The author suggest that the divide
should return a defined value, Inf, according to the IEEE floating point
standard. FreeBSD generates SIGFPE. I temporarily patched the code
locally to check for a delta of zero and arbitrarily set it to 1.0 so
that the divide succeeds and everything comes out ok without crashing.
Is FreeBSD's behavior correct? Why or why not? You can use the included
code snippet to verify that this occurs.
Thanks,
Nate
-- Forwarded message --
Date: Mon, 24 Apr 2000 15:54:38 -0700 (PDT)
From: David Mosberger [EMAIL PROTECTED]
To: Nate Lawson [EMAIL PROTECTED]
Subject: Re: patch to httperf-0.6
On Mon, 24 Apr 2000 15:37:21 -0700 (PDT), Nate Lawson [EMAIL PROTECTED] said:
Nate On x86. Your code generates SIGFPE, not SIGBUS sorry. Here
Nate is a code snippet which generates SIGFPE as well.
Nate main() { float a, b, c;
Nate a = 1.0; b = 0.0; c = a/b; }
Nate This seems to be correct behavior.
No, IEEE says that the exceptions should be disabled by default. You
should get Inf instead of SIGFPE.
--david
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Re: floating point exceptions
On Mon, Apr 24, 2000 at 11:44:59PM -0700, Nate Lawson wrote:
I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the
httperf-0.6 port gives a SIGFPE and dumps core when run against a system
that has no web server running. (The default behavior is to measure
localhost when no arguments are specified).
It seems this is caused by a divide by zero error since the delta between
connections ends up being zero. The author suggest that the divide
should return a defined value, Inf, according to the IEEE floating point
standard. FreeBSD generates SIGFPE. I temporarily patched the code
locally to check for a delta of zero and arbitrarily set it to 1.0 so
that the divide succeeds and everything comes out ok without crashing.
Is FreeBSD's behavior correct? Why or why not? You can use the included
code snippet to verify that this occurs.
FreeBSD has traditionaly violated the IEEE FP standard in this regard.
This is fixed in 5.0 and I think in 4.0-STABLE (though I can't remember
what file this is in so I can't check.) If upgrading to -stable isn't
an option you can add a call to fpsetmask(3) in the application as
follows (this will work on Solaris and Irix as well):
#include ieeefp.h
...
main() {
declare things
fpsetmask(0);
...
}
-- Brooks
--
Any statement of the form "X is the one, true Y" is FALSE.
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Re: floating point exceptions
OK, having to call fpsetmask(0) is an acceptable workaround. So if I
do:
#ifdef __freebsd___
fpsetmask(0);
#endif
Then this should work on all versions of freebsd?
--david
On Tue, 25 Apr 2000 00:05:23 -0700, Brooks Davis [EMAIL PROTECTED]
said:
Brooks On Mon, Apr 24, 2000 at 11:44:59PM -0700, Nate Lawson wrote:
I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the
httperf-0.6 port gives a SIGFPE and dumps core when run against a
system that has no web server running. (The default behavior is
to measure localhost when no arguments are specified).
It seems this is caused by a divide by zero error since the delta
between connections ends up being zero. The author suggest that
the divide should return a defined value, Inf, according to the
IEEE floating point standard. FreeBSD generates SIGFPE. I
temporarily patched the code locally to check for a delta of zero
and arbitrarily set it to 1.0 so that the divide succeeds and
everything comes out ok without crashing.
Is FreeBSD's behavior correct? Why or why not? You can use the
included code snippet to verify that this occurs.
Brooks FreeBSD has traditionaly violated the IEEE FP standard in
Brooks this regard. This is fixed in 5.0 and I think in 4.0-STABLE
Brooks (though I can't remember what file this is in so I can't
Brooks check.) If upgrading to -stable isn't an option you can add
Brooks a call to fpsetmask(3) in the application as follows (this
Brooks will work on Solaris and Irix as well):
Brooks #include ieeefp.h ... main() { declare things
Brooks fpsetmask(0); ... }
Brooks -- Brooks
Brooks -- Any statement of the form "X is the one, true Y" is
Brooks FALSE.
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Re: floating point exceptions
On Tue, Apr 25, 2000 at 07:47:01AM -0700, David Mosberger wrote: OK, having to call fpsetmask(0) is an acceptable workaround. So if I do: #ifdef __freebsd___ fpsetmask(0); #endif Then this should work on all versions of freebsd? #ifdef __FreeBSD__ fpsetmask(0); #endif BTW: if you update httperf, let me know so I can update the port (I'm the maintainer for the httperf port). -- Will Andrews [EMAIL PROTECTED] GCS/E/S @d- s+:++:- a---+++ C++ UB P+ L- E--- W+++ !N !o ?K w--- ?O M+ V-- PS+ PE++ Y+ PGP t++ 5 X++ R+ tv+ b++ DI+++ D+ G+ e- h! r--+++ y? To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
