Dear all,
I realize after reading this message below that you can actually time your
programming running speed in terms of seconds. Could somebody please tell me
which command it is? I tried to do "search time" and "search speed", but
only non-relevant commands came up.
Thank you in advance,
Guanghui Li
----- Original Message -----
From: "William Gould, Stata" <[email protected]>
To: <[email protected]>
Sent: Thursday, January 16, 2003 7:12 AM
Subject: Re: st: Speed issues with Stata 8
> Fred Wolfe <[email protected]> asked about Stata 8's speed in
> two contexts:
>
> 1. -use- and -merge-
>
> 2. -graph-
>
> In this posting, I want to address (1).
>
>
> Is Stata 8 slower using datasets?
> ---------------------------------
>
> Stata 8 is just as fast saving and using datasets as Stata 7. Fred,
however,
> observed that Stata 8 appears to be 10 times slower! Using Stata 8, Fred
> needs to -use- his old Stata 7 datasets and then -save- them again:
>
> . use <whatever>
> . save, replace
>
> That will convert Fred's datasets into Stata 8 format, and thereafter, the
> quickness Fred expects will return.
>
>
> Why resaving datasets speeds up -use-
> -------------------------------------
>
> Stata 8 allows 26 new missing-value codes with the result that,
internally,
> Stata stores missing values differently. When you -use- (or -merge- or
> -append-) an old-format dataset, Stata not only loads the dataset, Stata
> converts it as well.
>
> As an example, I created a 130MB dataset containing 200,000 observations
> on 200 variables using Stata 7. Using Stata 7,
>
> time to -save- 0.95 seconds
> time to -use- 1.32 seconds
>
> Then I fired up Stata 8 and used this Stata-7 format dataset:
>
> time to -use- 8.92 seconds
>
> Still in Stata 8, I resaved the data and tried -use- again:
>
> time to -save, replace- 0.95 seconds
> time to -use- 1.25 seconds
>
> In this example, the time to convert is substantial, being 8.92 - 1.25 =
7.67
> seconds. That same overhead will appear in -merge- and -append- if I
> leave the dataset in Stata-7 format.
>
> In smaller datasets, the conversion time is hardly noticable.
>
> It is convenient that Stata can work with old datasets without you needing
to
> convert them into modern format, but understand that Stata is converting
your
> datasets on the fly each and every time you work with them. With large
> datasets, I recommend converting the datasets only once.
>
> -- Bill
> [email protected]
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
