faq 1.#QNAN00000000 and -1.#IND000000000

[fcvcnet]

Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?
Thanks.

[Kavya]

fcvcnet wrote:

Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?

If you can post your code then it might be more easy to find the
problem.

[Jim Langston]

"fcvcnet" <fc*****@163.comwrote in message
news:ei**********@news.cn99.com...

Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?
Thanks.

NAN is not a number. This can happen with a floating point math won't work.
In some cases dividing by 0 will produce a NAN, but in others it produces
infinity (not sure if the specs say whiat it should produce).

Not sure what IND is. It may be infinity, but I would think that would be
INF, so I'm not sure.

[Marcus Kwok]

Jim Langston <ta*******@rocketmail.comwrote:

"fcvcnet" <fc*****@163.comwrote in message
news:ei**********@news.cn99.com...

>Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?
Thanks.

NAN is not a number. This can happen with a floating point math won't work.
In some cases dividing by 0 will produce a NAN, but in others it produces
infinity (not sure if the specs say whiat it should produce).

Not sure what IND is. It may be infinity, but I would think that would be
INF, so I'm not sure.

I'm not sure either, but IND might mean "indeterminate". As in,
(informally) 1/0 is infinity but 0/0 is indeterminate.

http://mathworld.wolfram.com/Indeterminate.html

--
Marcus Kwok
Replace 'invalid' with 'net' to reply

[Geo]

fcvcnet wrote:

Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?
Thanks.

recently I had to do some experimentation with this stuff, here's some
code and the output
float pinf = std::numeric_limits<float>::infinity();
double dpinf = std::numeric_limits<double>::infinity();

float ninf = -std::numeric_limits<float>::infinity();
float zero = 0.0;
float NaN = std::numeric_limits<float>::quiet_NaN();
float nNaN = -std::numeric_limits<float>::quiet_NaN();
double dNaN = std::numeric_limits<double>::quiet_NaN();

float xNaN = static_cast<float>(dNaN);

std::cout << "+ve infinity " << pinf << "\n";
std::cout << "-ve infinity " << ninf << "\n";
std::cout << "+ve QNAN " << NaN << "\n";
std::cout << "+ve dQNAN " << dNaN << "\n";
std::cout << "+ve xQNAN " << xNaN << "\n";
std::cout << "-ve QNAN " << nNaN << "\n";
std::cout << "+inf = +inf " << (pinf == pinf) << "\n";
std::cout << "+inf <= +inf " << (pinf <= pinf) << "\n";
std::cout << "+inf = +dinf " << (pinf == dpinf) << "\n";
std::cout << "+inf = -inf " << (pinf == ninf) << "\n";
std::cout << "+inf / +inf " << pinf/pinf << "\n";
std::cout << "+inf / -inf " << pinf/ninf << "\n";
std::cout << "+inf / zero " << pinf/zero << "\n";
std::cout << "+inf * -inf " << pinf*ninf << "\n";
std::cout << "+inf + -inf " << pinf+ninf << "\n";
std::cout << "+inf + +inf " << pinf+pinf << "\n";
std::cout << "+inf - -inf " << pinf-ninf << "\n";
std::cout << "+inf - +inf " << pinf-pinf << "\n";
std::cout << "-inf - -inf " << ninf-ninf << "\n";
std::cout << "\n\n";
std::cout << "NaN = NaN " << (NaN == NaN) << "\n";
std::cout << "-NaN = -NaN " << (nNaN == nNaN) << "\n";
std::cout << "-NaN = NaN " << (nNaN == NaN) << "\n";
std::cout << "NaN = -NaN " << (NaN == nNaN) << "\n";
std::cout << "NaN = +inf " << (NaN == pinf) << "\n";
std::cout << "NaN = -inf " << (NaN == ninf) << "\n";
std::cout << "0 / zero " << 0/zero << "\n";

+ve infinity 1.#INF
-ve infinity -1.#INF
+ve QNAN 1.#QNAN
+ve dQNAN 1.#QNAN
+ve xQNAN 1.#QNAN
-ve QNAN -1.#IND
+inf = +inf 1
+inf <= +inf 1
+inf = +dinf 1
+inf = -inf 0
+inf / +inf -1.#IND
+inf / -inf -1.#IND
+inf / zero 1.#INF
+inf * -inf -1.#INF
+inf + -inf -1.#IND
+inf + +inf 1.#INF
+inf - -inf 1.#INF
+inf - +inf -1.#IND
-inf - -inf -1.#IND
NaN = NaN 0
-NaN = -NaN 0
-NaN = NaN 0
NaN = -NaN 0
NaN = +inf 0
NaN = -inf 0
0 / zero -1.#IND

[Geo]

Meant to say, results are from gcc on pentium, and seem to agree with
IEEE 754. VC 6.0 results differ for some cases, VC 7.0 is the same as
gcc.

[fcvcnet]

Thanks you very much.

"Geo" <[e-mail]>
??????:11********************@e3g2000cwe.googlegro ups.com...

Meant to say, results are from gcc on pentium, and seem to agree with
IEEE 754. VC 6.0 results differ for some cases, VC 7.0 is the same as
gcc.

[fcvcnet]

Thanks you very much.
"Marcus Kwok" <ri******@gehennom.invalidдÈëÏûÏ¢ÐÂÎÅ:ei********* *@news-int2.gatech.edu...

Jim Langston <ta*******@rocketmail.comwrote:

>"fcvcnet" <fc*****@163.comwrote in message
news:ei**********@news.cn99.com...

>>Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme,
what
happened?
why?
Thanks.

NAN is not a number. This can happen with a floating point math won't
work.
In some cases dividing by 0 will produce a NAN, but in others it produces
infinity (not sure if the specs say whiat it should produce).

Not sure what IND is. It may be infinity, but I would think that would
be
INF, so I'm not sure.

I'm not sure either, but IND might mean "indeterminate". As in,
(informally) 1/0 is infinity but 0/0 is indeterminate.

http://mathworld.wolfram.com/Indeterminate.html

--
Marcus Kwok
Replace 'invalid' with 'net' to reply

[fcvcnet]

Thanks you very much.

"Jim Langston" <ta*******@rocketmail.comдÈëÏûÏ¢ÐÂÎÅ:Cz********** ***@newsfe07.lga...

"fcvcnet" <fc*****@163.comwrote in message
news:ei**********@news.cn99.com...

>Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme,
what happened?
why?
Thanks.

NAN is not a number. This can happen with a floating point math won't
work. In some cases dividing by 0 will produce a NAN, but in others it
produces infinity (not sure if the specs say whiat it should produce).

Not sure what IND is. It may be infinity, but I would think that would be
INF, so I'm not sure.

[fcvcnet]

Marcus Kwok
Thanks you very much.
your url
http://mathworld.wolfram.com/Indeterminate.html

is very useful!
Thanks again!

[cts]

Odd that no one seems to have brought up errno.

When something in the C libraries, like the math library, fails, the
global variable errno is set. If you get a value of #QNAN or #IND,
it's likely that an error in the standard math library. You can easily
check this after an operation and you can get a nice string
representation of the error message too.

example:

#include <cmath>
#include <cstring>
#include <iostream>

errno = 0; // clear out any previous errors

// example math call
y = std::atan(x); // we suspect that something screwy happens here,
maybe 'x' is a bad value

// check if there was a catastrophe, if yes, print out the error
message
if (errno)
std::cout << strerror(errno) << std::endl;

fcvcnet wrote:

Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme, what
happened?
why?
Thanks.

[fcvcnet]

Thanks you very much.

"cts" <sm*****@gmail.com>
??????:11*********************@f16g2000cwb.googleg roups.com...

Odd that no one seems to have brought up errno.

When something in the C libraries, like the math library, fails, the
global variable errno is set. If you get a value of #QNAN or #IND,
it's likely that an error in the standard math library. You can easily
check this after an operation and you can get a nice string
representation of the error message too.

example:

#include <cmath>
#include <cstring>
#include <iostream>

errno = 0; // clear out any previous errors

// example math call
y = std::atan(x); // we suspect that something screwy happens here,
maybe 'x' is a bad value

// check if there was a catastrophe, if yes, print out the error
message
if (errno)
std::cout << strerror(errno) << std::endl;

fcvcnet wrote:

>Hi,
I got result 1.#QNAN00000000 and -1.#IND000000000 in my programme,
what
happened?
why?
Thanks.

[fcvcnet]

#include "stdafx.h"
#include <cmath>
#include <cstring>
#include <iostream>

int main(int argc, char* argv[])
{
errno = 0;
double i,j;
i=1;
j=0;
double y = i/j;
if (errno)
std::cout << strerror(errno) << std::endl;
std::cin >i;
return 0;
}
I tried , but I saw nothing. My code right?