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Re: st: Memory & speed: Stata 7 + Mac OS X


From   kturner@stata.com (Kevin Turner)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Memory & speed: Stata 7 + Mac OS X
Date   Tue, 18 Feb 2003 10:40:36 -0600

Ferry, Danielle (DFerry@gc.cuny.edu) wrote:

> Memory: Setting the memory in Stata 7 on a Mac OS X box requires the user to
> set the memory in the General Preferences pull-down menu and then to quit &
> relaunch Stata. Any chance this has been fixed in Stata 8? (That would be
> enough to get me to upgrade!)

Due to the unix underpinnings of MacOS X and the fact that Stata8 only 
supports MacOS X, the memory management mimics that of unix. This means 
that the amount of memory allocated for data can be changed dynamically 
using the -set memory- command without having to restart Stata (as was 
common under pre-OSX versions of the OS).

> Speed: I have found that using a 200 MB dataset is really ugly. On a G4
> (again, Stata 7 & OS X), it takes nearly a minute just to tabulate a
> variable. I don't think this is a problem w/ my computer since I have tried
> it on both a G3 and G4 w/ maxed out RAM. I do not have this speed problem on
> my PC. Has anyone experienced this or can anyone attest to the elimination
> of this problem on Stata 8? Since Stata 7 was originally written for OS 9
> and then an OS X fix was released, I am wondering if this could be the root
> of the problem.

Comparing speed between various computers, especially those with different 
architectures can be tricky business. Having said that, I offer the following
tests for consideration. 

Under Stata8 SE, I ran the following set of commands on two machines. Both 
had sufficient RAM. The first machine was a 700Mhz Celeron running Win 2000
and it ran the tabulate command in 4.45 seconds. The second machine was a 
466Mhz Mac running OS X, and it ran the tabulate command in 9.93 seconds.

. set rmsg on
. set mem 220m
. set more off
. sysuse auto
. expand 60000
. tabulate mpg

It may be that the difference you are experiencing is due to too much memory 
being allocated, forcing the Mac to use virtual memory (swap space).

--Kevin 
kturner@stata.com
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