st: RE: processing time

["McKenna, Timothy" <Timothy.McKenna@NERA.com>]

I think dropping both in one step is faster:

Profiler results:

both
    99   75.021  both
Overall total count =     99
Overall total time  =     75.021 (sec)



separate
    99   96.438  separate
Overall total count =     99
Overall total time  =     96.438 (sec)



-------------- Begin do file ------------------- 

#delimit;
version 9.2;
capture program drop _all;

clear;
set mem 100m;
set seed 12345;

set obs 1000000;
local tests 100;

gen a = uniform(); qui replace a = . if a > 0.5;
gen b = uniform(); qui replace b = . if b > 0.5;

program define both;
preserve;
quietly drop if a == . | b == .;
restore;
end;

program define separate;
preserve;
quietly drop if a == .;
quietly drop if b == .;
restore;
end;

profiler on;
local i = 1;
while `i' < `tests' {;
	both;
	local i = `i' + 1;
	};
profiler off; profiler report; profiler clear;

profiler on;
local i = 1;
while `i' < `tests' {;
	separate;
	local i = `i' + 1;
	};
profiler off; profiler report; profiler clear;

-------------- End do file ------------------- 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Jon Schwabish
Sent: Thursday, March 22, 2007 12:55 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: processing time

Quick question:

Which is more efficient (in terms of processing time)?

drop if a==.
drop if b==.

  OR 

drop if a==. | b==.

(where a and b are any variables of choice).

Thanks.


 
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