Most today's platforms are native 64 bit
and 64 bit applications are to be preferred. The current version of
SWI-Prolog primarily targets 64 bit platforms. 32-bit platforms are
still supported as they are used on embedded devices and the WASM (Web
Assembly, see section 13)
still has poor support for 64 bits.
While the (currently) stable 9.2 series still has a real 32 bit
version were Prolog data structures are based on 32 bit word
units, the 9.3 development series represents all Prolog data as 64 bit
units, regardless of the hardware's pointer size. This provides better
uniformity and avoids the 128Mb stack limit of the 32-bit 9.2 series.
Choices in the data representation such as the placement and number
of
tag bits are still based on 32-bit units. This is expected to
change in due time, simplifying the code and improving performance.
