Re: [boost] Optimized portable isnan, isfinite, fpclassify etc

From: John Maddock (john_at_[hidden])
Date: 2006-10-12 13:03:19

John Maddock wrote:
> Johan Råde wrote:
>> The problem is <boost/endian.hpp>.
>> According to <boost/detail/endian.hpp> the platform is little endian.
>> But it is clearly big endian.
>
> One thing you've got to watch here is that the endianness of ints and
> pointers isn't necessarily the same as that for reals.
>
> And just to throw a spanner in the works, I believe the Itanium can
> have
> it's endianness altered at runtime.  Whether any OS's will let you do
> that without crashing your program, I don't know, but I could
> certainly see uses for changing the endianness of reals at runtime
> (think big distributed applications, running over mixed hardware).

Some searching around the web seems to confirm this, indeed it appears that 
Linux on Itanium is LE, but HP-UX on Itanium is BE.  And HP-UX on either 
Itanium or PA-RISC appears to be able to handle data in either BE or LE 
depending on the setting of one hardware bit.

John.