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RE: st: time elapsed within 'for' loops


From   Mark Schaffer <M.E.Schaffer@hw.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: time elapsed within 'for' loops
Date   Sun, 14 Nov 2004 17:22:27 +0000 (GMT)

-profiler- should still give David almost what he wants, even if he doesn't
use -foreach-.  I just tried a -reshape- with -profiler-, and most of the
time spent reshaping was in the the subroutine -Wide-.  Presumably there is
another subroutine -Long-.  If these are where most of the time is spent
reshaping David's data, he'll something not too far from the right answer to
his question.

Cheers,
Mark

Quoting Nick Cox <n.j.cox@durham.ac.uk>:

> It is indeed what David wants, but 
> -profiler- neither promises to 
> give this information nor in 
> fact gives it. 
> 
> "The record includes only the time spent 
> directly in a program and not time spent 
> in other programs that are themselves 
> invoked by the program -- these latter 
> times are recorded with the invoked program." 
> 
> You may be carrying over ideas associated
> with -for- in other languages in which 
> -for- controls a loop. -for- in Stata 
> does that too, but it is nothing other 
> than an .ado that runs other commands 
> or programs. (There also can be a major 
> interpretive overhead. I used to use 
> -for- a long time ago to cycle over
> stuff, until it became clear that -for- 
> itself was sometimes taking many times longer
> than what I wanted.) 
> 
> In this respect, -for- contrasts sharply 
> with -foreach- or -forvalues-, which 
> are wired into the executable. Having 
> said that, I am not clear that using
> -foreach- here would get the profiling 
> desired. 
> 
> Nick 
> n.j.cox@durham.ac.uk 
> 
> > -----Original Message-----
> > From: owner-statalist@hsphsun2.harvard.edu
> > [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of 
> > Mark Schaffer
> > Sent: 14 November 2004 16:27
> > To: statalist@hsphsun2.harvard.edu
> > Subject: RE: st: time elapsed within 'for' loops
> > 
> > 
> > Nick/David,
> > 
> > Quoting Nick Cox <n.j.cox@durham.ac.uk>:
> > 
> > > I doubt it. -for- itself is a command. The fact 
> > > that it runs other commands is not reflected 
> > > by what the profiler reports,
> > 
> > reshape is an ado, and so profiler should report on how much 
> > time was spent
> > in reshape, no?  I think this is what David wants.  Or 
> > perhaps I missed the
> > point somewhere.
> > 
> > Cheers,
> > Mark
> > 
> > > as is explained 
> > > in the help Mark quotes here. 
> > > 
> > > A quite different comment is beware -for- 
> > > and the habit of trying to write miniature programs 
> > > as a single call to -for-. It is cute when it 
> > > works but very inefficient and all too likely to bite you. 
> > > 
> > > Nick 
> > > n.j.cox@durham.ac.uk 
> > > 
> > > Mark Schaffer
> > > 
> > > > Try -profiler-; it will probably do what you want.  From the
> 
> > > > help file:
> > > > 
> > > > "profiler is a programmer's command that can help in 
> > > > optimizing ado-files
> > > > and other Stata programs.  When profiling is turned on, 
> > > > profiler on, Stata
> > > > begins keeping a record of each time a program is run and how
> 
> > > > much time is
> > > > spent in the program."
> > >  
> > > David K Evans
> > >  
> > > > > Is there a simple way to see how much time has elapsed while
> a
> > > > > command in the midst of a "for" loop is running?
> > > > > 
> > > > > Outside of a loop, I just "set rmsg on" and can see how
> long
> > > each
> > > > > command takes.
> > > > > 
> > > > > But if I have, for example,
> > > > > 
> > > > > for num 1/10: preserve \ keep if age==X \ reshape [blah
> blah
> > > blah]
> > > > > \
> > > > > save ageX.dta, replace \ restore;
> > > > > 
> > > > > and I want to know how long the reshaping took, I'm not sure
> how
> > > to
> > > > > find out. "set rmsg on" only gives me the time for the
> entire
> > > loop.
> > > > > 
> > > > > I know about macros to display the time, but I'm not sure
> how
> > > to
> > > > > manipulate them to calculate time elapsed.
> > > 
> 
> *
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> 



Prof. Mark Schaffer
Director, CERT
Department of Economics
School of Management & Languages
Heriot-Watt University, Edinburgh EH14 4AS
tel +44-131-451-3494 / fax +44-131-451-3008
email: m.e.schaffer@hw.ac.uk
web: http://www.sml.hw.ac.uk/ecomes
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