Rémi Zara írta:
> Le 24 févr. 2010 à 18:58, Boszormenyi Zoltan a écrit :
>
>> Here's the attached test code. Compile it with
>>
>> gcc -Wall -o nantest nantest.c -lm
>>
>> and run it. It tests NAN anf INFINITY values with isinf() and isnan().
>> The expected output is:
>>
>> ==================
>> $ ./nantest
>> computed NAN
>> 1 0
>> computed INFINITY
>> 0 1
>> ==================
>>
>> Instead of "computed", NetBSD/x86-64 prints "defined"
>> but the test results are the same as under Linux/x86-64.
>>
>>
>
> Here it is :
>
First, thanks for running it.
> -bash-4.1$ gcc -Wall -o nantest nantest.c -lm
> -bash-4.1$ ./nantest
> defined NAN
> 0 1
>
So: isnan((double)NAN) == false, isinf((double)NAN) == true?
No wonder this causes a little problem.
> defined INFINITY
> 0 1
>
> Ok. So, on NetBSD/mips (#ifdef __NetBSD__ && __mips__), isnan(NAN) is true,
> isnan((double)NAN) is false, and isnan((double)(0.0 / 0.0)) is true.
>
> Regards,
> Rémi Zara
>
NAN on NetBSD/x86-64 is defined as:
extern const union __float_u __nanf;
#define NAN __nanf.__val
I would guess that it's similar on mips. Is is possible that
NetBSD/mips has a conversion bug?
What I don't get is that the code I used in ECPG and in this
test code is the same as in src/backend/utils/adt/float.c. E.g.:
float8in sees "NaN" -> value will be (double)NAN
float8out sees isnan(value) -> outputs "NaN" string
Can someone shed some light on why the backend
doesn't get the problem as above? :-(
As Rémi says, isnan((double)(0.0 / 0.0)) == true for him.
Michael: IIRC, IEEE754 explicit about that the (0.0/0.0) division
produces NaN. How about doing it explicitely in ECPG?
Rémi: please, run this code to confirm the above?
Best regards,
Zoltán Böszörményi
--
Bible has answers for everything. Proof:
"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more
than these cometh of evil." (Matthew 5:37) - basics of digital technology.
"May your kingdom come" - superficial description of plate tectonics
----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/
#include <math.h>
#include <float.h>
#include <stdio.h>
static double
get_float8_nan(void)
{
printf("computed NAN\n");
return (double) (0.0 / 0.0);
}
static double
get_float8_infinity(void)
{
#ifdef INFINITY
printf("defined INFINITY\n");
return (double) INFINITY;
#else
printf("computed INFINITY\n");
return (double) (HUGE_VAL * HUGE_VAL);
#endif
}
int main(void) {
double d;
d = get_float8_nan();
printf("%d %d\n", isnan(d), isinf(d));
d = get_float8_infinity();
printf("%d %d\n", isnan(d), isinf(d));
return 0;
}
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