joe <jhughesjr@xxxxxxxxxxx> writes: > I guess in my situation, even if the 80 bit extended precision registers > are supposed to be more accurate/precise overall, the accuracy/precision > is not as important to me than having a number print out the same > regardless of the platform it is running on, which really is my main goal. Yes, getting the standard IEEE behavior for comparing results across platforms is really useful. On x86 systems it is possible to put the processor into the standard IEEE double precision mode by setting the floating point control word. For GNU/Linux the header file /usr/include/fpu_control.h has macros _FPU_GETCW and _FPU_SETCW for changing the settings. These macros are internal (I haven't seen a documented interface to them) but you can see how they work there anyway -- it is one line of inline assembly. If you look in the IEEE chapter of the GNU Scientific Library Reference Manual (http://www.gnu.org/software/gsl/) there is some discussion about this and a function which allows you to set all the parameters of the fpu mode from an enviroment variable. -- Brian Gough Network Theory Ltd, Publishing "An Introduction to GCC" --- http://www.network-theory.co.uk/
