Thank you. We, then, in effect, are carrying around 'dead bytes' on amd64, for, reason?
That is, what is the 'win' in doing this ? This is of no consequence for a handful of long doubles, but big arrays of long double.... (This is just curiosity; I have found exactly one scientific calculation I needed to do whose precision improved using long doubles, a satellite orbital prediction over very long times) -Mike On Fri, Jul 5, 2024 at 9:35 PM Martin Husemann <mar...@duskware.de> wrote: > On Fri, Jul 05, 2024 at 07:13:05PM -0700, Michael Cheponis wrote: > > sizeof(long double) reports 16 in both amd64 and arm64. I think that > amd64 > > uses 80-bit long double floats, and arm64 uses 128-bit long double > floats. > > See enclosed code. > > The storage size of a long double is one thing, but the exact format > used in calculations may vary. > > On amd64: > > > cc -dM -E - < /dev/null | fgrep LDBL_MANT > #define __LDBL_MANT_DIG__ 64 > > > On aarch64: > > > cc -dM -E - < /dev/null | fgrep LDBL_MAN > #define __LDBL_MANT_DIG__ 113 > > (use just LDBL in the fgrep to see more exact limits of the format in use) > > Martin >
