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Re: Alignment of gfortran allocated arrays
John Travers wrote:
On 17/08/07, Tim Prince <tprince@computer.org> wrote:
malloc() hardly qualifies as a gfortran internal.
I never meant to imply that it was.
It has been around
since long before gfortran or SSE. The 32-bit glibc malloc(), if that's
what you're discussing, is likely to continue as it has been for over 10
years, supporting double precision but not SSE objects. Note that
gfortran runs on a lot of systems besides those which depend on 32-bit
glibc, so if that is your world, you might clarify your posts by so
stating. As there aren't any more CPUs manufactured which don't support
64-bit OS, you might take into account that many of us use 64-bit. Not
Yes, my two primary systems (including the one I posted from) are 64
bit. I thought it was clear what I was talking about as we were
discussing getting 16-byte alignment.
16-byte alignments are needed for SSE support on both 32- and 64-bit
OS. Various compilers for 32-bit linux handle it in incompatible ways.
You could get into trouble calling a vectorized gcc or gfortran
function from ifort, for example. malloc() gives 4-byte alignment on
32-bit Windows (even scalar double precision performance may suffer),
and 8-byte on linux.
Windows and linux 64-bit both adopted 16-byte alignment as a default.
If malloc() doesn't give a 16-byte aligned pointer, that's a bug. The
URLs you referenced indicate that gfortran already has resolved the
ALLOCATABLE problem as far as 64-bit linux is concerned. Solaris is the
only 64-bit OS I know of which has trouble here.