Date:         Fri, 4 Feb 2011 20:33:04 -0800
Reply-To:     Jack Hamilton <jfh@STANFORDALUMNI.ORG>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Jack Hamilton <jfh@STANFORDALUMNI.ORG>
Subject:      Re: Newbee question regarding keep option
Comments: To: Arthur Tabachneck <art297@ROGERS.COM>
In-Reply-To:  <201102041429.p14BlDLn008746@waikiki.cc.uga.edu>
Content-Type: text/plain; charset=iso-8859-1

Just out of curiosity, what happens if you make the data step in test 3 a data step view instead?

On Feb 4, 2011, at 6:29 AM, Arthur Tabachneck wrote:

> In another of this week's threads Sterling was asking how to speed up a proc
> means he was running.  I think that Søren probably provided what was needed.
>
> I was going to ask Sterling if the input file contained a LOT of variables
> that weren't being considered in the desired analysis.  However, I decided
> to test my suggestion before asking the question.
>
> Given a test like that shown below, I have always thought that test2 was the
> same as test3 other than, of course, possibly some IO time reading in the
> wider file.  I was quite surprised in the differences not just in real time,
> but in CPU time.
>
> Test1 and Test2 run at about the same speed, although with a lot of variance
> between replications.
>
> Test3 runs incredibly faster!  Is that what everyone would have expected?  I
> have always been under the impression that the keep statement got rid of the
> unnecessary baggage.
>
> /* Create test data */
> data a;
>  array jj(1000);
>  array kk(1000);
>  do i=1 to 100000;
>    do j=1 to 1000;
>   jj(j)=rannor(0);
> end;
> do k=1 to 1000;
>   kk(k)=rannor(0);
>    end;
> ii=mod(i,50);
> output;
>  end;
> run;
>
> /* Test 1 */
> proc means noprint missing nway data = a;
>   var jj1 jj2 jj3 jj5;
>   class ii;
>   output out = t1 (drop = _TYPE_ _FREQ_) sum()=;
> run;
>
> /* Test 2 */
> proc means noprint missing nway data = a
>  (keep=ii jj1 jj2 jj3 jj4 jj5);
>   var jj1 jj2 jj3 jj4 jj5;
>   class ii;
>   output out = t2 (drop = _TYPE_ _FREQ_) sum()=;
> run;
>
> /* Test 3 */
> data b;
>  set a (keep=ii jj1 jj2 jj3 jj4 jj5);
> run;
> proc means noprint missing nway data = b;
>   var jj1 jj2 jj3 jj4 jj5;
>   class ii;
>   output out = t3 (drop = _TYPE_ _FREQ_) sum()=;
> run;
>
> Art