[R-SIG-Mac] How to make Mac 64-bit version feature complete?
ono at java.pl
Fri Dec 16 19:38:28 CET 2011
Just to give you some numbers, on my iMac Lion 10.7.2, i5 Sandy Bridge.
• When allocating matrix 10000x10000 R64 takes 798MB vs R32 taking 785MB, so 14MB is wasted for 64-bit handling
• Running R-benchmark-25.R from http://r.research.att.com/benchmarks/ in R64 renders about ~5% performance gain
I am aware these number can really differ on older OSX, notably on Leopard, also 64-bit performance can be very bad for 64-bit using vecLib on older OSX, vecLib was somehow borked by Apple.
On other side Apple depreciates slowly 32-bit in newer systems, in Lion there's no 32-bit kernel anymore, most of built-in apps are 64-bit only. Still is can run 32-bit apps, but it cannot run PPC anymore (no Rosetta).
So IMHO the picking 64-bit on 10.6+ (or 10.7+) is good option for the future, as the scientific datasets grow every year and RAM installed by default by Apple will be soon min 8GB.
(Some tech blather: 64-bit program can allocate in fact more than 4GB when having only 4GB RAM - implies paging and swapping, unless allocated pages remain non-written. In theory 64-bit program can allocate few 1TB on 4GB RAM system, with no physical memory usage bump. Memory will be used only when user will 1st access the allocated pages.)
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