Robert Bradshaw wrote:
>>>
>>>>> **********************************************************************
>>>>> File "/rootpool2/local/kirkby/sage-4.3/devel/sage/sage/symbolic/
>>>>> pynac.pyx", line
>>>>> 1276:
>>>>> sage: py_exp(float(1))
>>>>> Expected:
>>>>> 2.7182818284590451
>>>>> Got:
>>>>> 2.7182818284590455
> Yes, that could be the difference for exp. What's more worrisome is
> that the C compiler incorrectly resolves the literal floating point
> 2.7182818284590452354 .
>
> - Robert
>
Em, This is very odd. exp(1) gives a different result on SPARC if you build
with gcc or Sun Studio. GCC is correct, and Sun Studio is wrong. Yet Sage on
't2' was build with gcc, not Sun Studio.
On Open Solaris, using a Xeon processor, the two compilers give the same result.
Here's a noddy C program:
drkir...@kestrel:~$ cat exp.c
#include <math.h>
#include <stdio.h>
int main() {
printf("%.16lf\n",exp(1.0));
}
This data below is from a SPARC (sun4u architecture) of mine. I've tried on
't2'
(sun4v) and get exactly the same results.
drkir...@kestrel:~$ uname -a
SunOS kestrel 5.10 Generic_141444-09 sun4u sparc SUNW,UltraAX-i2
drkir...@kestrel:~$ cat exp.c
#include <math.h>
#include <stdio.h>
int main() {
printf("%.16lf\n",exp(1.0));
}
drkir...@kestrel:~$ gcc exp.c
drkir...@kestrel:~$ ./a.out
2.7182818284590451
drkir...@kestrel:~$ /opt/sunstudio12.1/bin/cc -lm exp.c
drkir...@kestrel:~$ ./a.out
2.7182818284590455
Now, when I do this on Open Solaris, I get the same result with each compiler.
bash-3.2$ uname -a
SunOS hawk 5.11 snv_111b i86pc i386 i86pc
bash-3.2$ gcc exp.c
bash-3.2$ ./a.out
2.7182818284590451
bash-3.2$ /opt/sunstudio12.1/bin/cc -lm exp.c
bash-3.2$ ./a.out
2.7182818284590451
I also tried this on HP-UX, and get the same (correct) result with both the
native HP compiler and with gcc.
-bash-4.0$ uname -a
HP-UX hpbox B.11.11 U 9000/785 2016698240 unlimited-user license
-bash-4.0$ gcc exp.c
-bash-4.0$ ./a.out
2.7182818284590451
-bash-4.0$ cc -lm exp.c
-bash-4.0$ ./a.out
2.7182818284590451
IMHO, this should not be covered up by reducing the number of digits compared,
but recorded as a failure. Many packages have 'expected failures'. It would be
better if this was recorded as an 'expected failure'. I appreciate that might
not be how the doctests work now.
Dave
PS
It's interesting how both HP and Sun compilers need the '-lm' to link in the
maths library. GCC does that by default.
http://trac.sagemath.org/sage_trac/ticket/7067
is an open ticket which is caused by making the incorrect assumption that the C
compiler will automatically link in the maths library.
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