Test Gromacs with X32 ABI
Given that we never need more than 4GB, X32 ABI (http://en.wikipedia.org/wiki/X32_ABI) shouldn't have any disadvantage and it could give us very slightly better performance. So it might be worth testing it.
Make source compile under Linux X32 ABI
The X32 ABI uses 32-bit pointers in combination with all
other features of x86-64 to save memory. This requires two
minor changes to x86 inline assembly macro checks, where we
need check for LP64 (64-bit pointers) rather than
x86_64 (which is set for X32). The resulting binaries
run approximately 2% faster, but since it requires all
dependent libraries to be available in X32 format it is
not something we will enable with a simple setting for now.
To use it manually, set CFLAGS and CXXFLAGS to "-O3 -mx32".
#1 Updated by Berk Hess over 4 years ago
- Status changed from New to Accepted
It seems floating point performance is nearly unaffected and we avoid pointer operations as much as possible in Gromacs, so I expect very little gain. But if it's easy to try, we should. On OpenSuse x32 libraries are not readily available. But for Ubuntu the situation seems to be better: