On Sun, 8 Apr 2007, Jon Forrest wrote:
The experiment I tried was to build several fairly large programs on Fedora Core 6 32 bit and then 64 bit using exactly the same hardware. This is clearly not the same kind of test as your example but it's more relevant as a systems-level comparison. If I remember, I built mysql and apache. This took about the same amount of time in both modes.
Building programs isn't a particularly good benchmark for anything but building programs, for all that people tend to use make as a benchmark anyway. RUNNING programs (other than make and gcc) is much better. For one thing, compilers tend to basically be parsing engines processing text, with very little advantage available due to e.g. optimizing loops or streaming in double precision data to do a complex numerical computation on.
I suspect that the Beowulf crowd would have lots of experience with 32-bits vs 64-bits question, so I'd welcome additional comments, especially dealing with situations where programs *don't* need the additional address space of the 64-bit model.
Sure. 64-bits = "good". 32-bits = "bad", in nearly all CPU-intensive (especially floating point intensive) applications that don't thrash the cache. Cache thrashing is actually more expensive IIRC for 64 bit systems than it is for 32 bit systems because the penalty for a cache miss is higher. For pretty much everything else, though, goood. And even where it is bad it isn't THAT bad because its good at least partly compensates. Size of the program isn't terribly important to this conclusion, as Toone's miniprogram clearly shows. You don't need a lot of code to do a long-running double precision loop. rgb
Cordially,
-- Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:[EMAIL PROTECTED] _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
