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Re: st: Stata (gllamm) benchmarks for different platforms?
Michael Ingre <Michael.Ingre@ipm.ki.se> wrote:
> Some time ago I asked about benefits from 64-bit G5 code on this list and
> the answer was that Stata already benefits from "greater double precision
> perfomance" on the G5 and that any improvement in speed from optimized code
> would be minimal.
> Now, I would like to challenge that statement. With Native 64-bit code on
> the G5, I would suggest the G5 to perform in par with the Opteron.
The G5 can be 3 to 4 times slower at memory access (confirmed by an Apple
engineer) in some cases which is most likely what you're seeing. When memory
access isn't an issue, we've seen the G5 outperform a higher clocked P4.
Our belief that any speed improvement from optimized code would be minimal was
based on the information we had at the time. In addition, an Apple engineer
personally told me that breaking the 4GB limit was very difficult in OS X at
that time (late 2003, when Panther was available) without inside knowledge and
help from Apple.
Apple has updated information pertaining to the G5 and Panther. From Apple's
"Panther features a redesigned kernel and updated system software math
libraries specifically for the 64-bit PowerPC G5 processor. The updated
kernel delivers the most substantial benefits of 64-bit computing by breaking
through the 4GB physical memory limit. The key functions of the system math
and vector libraries have been tuned to take maximum advantage of new and
faster math functions supported by the 64-bit G5. Moreover, unmodified
applications that use the system math functions will get an automatic
performance boost on the G5."
Apple's gcc compiler hasn't changed since we made our original statement so
we'll have to see what changes were made to Panther and how to take advantage
of them. It's unclear how much of improvement there will be when Stata is
optimized for the G5 but it is something we're looking into. However, it's
doubtful you're going to see the 3 to 4 times improvement you're hoping for
when we go 64-bit.
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