[Numpy-discussion] float128 / longdouble on PPC - is it broken?

[Derek Homeier]

On 25 Oct 2011, at 20:05, Matthew Brett wrote:

>>> Both the same as numpy:
>>> 
>>> [mb312 at jerry ~]$ gcc test.c
>>> test.c: In function 'main':
>>> test.c:5: warning: incompatible implicit declaration of built-in function
>>> 'powl'
>> 
>> I think implicit here means that that the arguments and the return values
>> are treated as integers. Did you #include <math.h>?
> 
> Ah - you've detected my severe ignorance of c.   But with math.h, the
> result is the same,
> 
> #include <stdio.h>
> #include <math.h>
> 
> int main(int argc, char* argv) {
>       long double x;
>       x = pow(2, 64);
>       x -= 1;
>       printf("%g %Lg\n", (double)x, x);
> }

What system/compiler is this? I am getting 
./ldouble                                                                                                                                     
1.84467e+19 1.84467e+19

and 

>>> res = np.longdouble(2)**64
>>> res
18446744073709551616.0
>>> 2**64
18446744073709551616L
>>> res-1
18446744073709551615.0
>>> np.__version__
'1.6.1'

as well as with 

>>> np.__version__
'2.0.0.dev-3d06f02'
[yes, not very up to date]

and for all gcc versions
/usr/bin/gcc -v                                                                                                                               
Using built-in specs.
Target: powerpc-apple-darwin9
Configured with: /var/tmp/gcc/gcc-5493~1/src/configure --disable-checking -enable-werror --prefix=/usr --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-transform-name=/^[cg][^.-]*$/s/$/-4.0/ --with-gxx-include-dir=/include/c++/4.0.0 --with-slibdir=/usr/lib --build=i686-apple-darwin9 --program-prefix= --host=powerpc-apple-darwin9 --target=powerpc-apple-darwin9
Thread model: posix
gcc version 4.0.1 (Apple Inc. build 5493)

to 

/sw/bin/gcc-fsf-4.6 -v                                                                                                                        
Using built-in specs.
COLLECT_GCC=/sw/bin/gcc-fsf-4.6
COLLECT_LTO_WRAPPER=/sw/lib/gcc4.6/libexec/gcc/powerpc-apple-darwin9.8.0/4.6.1/lto-wrapper
Target: powerpc-apple-darwin9.8.0
Configured with: ../gcc-4.6.1/configure --prefix=/sw --prefix=/sw/lib/gcc4.6 --mandir=/sw/share/man --infodir=/sw/lib/gcc4.6/info --enable-languages=c,c++,fortran,lto,objc,obj-c++,java --with-gmp=/sw --with-libiconv-prefix=/sw --with-ppl=/sw --with-cloog=/sw --with-mpc=/sw --with-system-zlib --x-includes=/usr/X11R6/include --x-libraries=/usr/X11R6/lib --program-suffix=-fsf-4.6 --enable-cloog-backend=isl --disable-libjava-multilib --disable-libquadmath
Thread model: posix
gcc version 4.6.1 (GCC)

uname -a
Darwin osiris.astro.physik.uni-goettingen.de 9.8.0 Darwin Kernel Version 9.8.0: Wed Jul 15 16:57:01 PDT 2009; root:xnu-1228.15.4~1/RELEASE_PPC Power Macintosh

Cheers,
						Derek