Date:         Wed, 9 Aug 2000 21:26:14 +1200
Reply-To:     Don Stanley <don_stanley@XTRA.CO.NZ>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Don Stanley <don_stanley@XTRA.CO.NZ>
Subject:      WHERE clause and PUT function -- inefficient comapred to IF
Content-Type: text/plain; charset=us-ascii

This might be useful .. esp if you're charged by CPU.

Be wary of using the dataset option WHERE=,  having a PUT function in
the WHERE, and using a user defined format. It can add a lot of extra
CPU time to your step.

Found this today under MVS 609E. Reading 6 million records as follows::

set x (where=(put(prod,$select.) eq 'Y') ;

took 210 seconds CPU. Changing this to

set x ;
if put(prod,$select.) eq 'Y' ;

took 130 CPU seconds.

We also noted this with a SAS dataset on tape, reducing CPU time from
100 seconds to 20 by swapping from the WHERE to an IF.

I reported this to SAS, nothing obvious on usage notes -- one hit on
WHERE being less efficient than IF related to short observation widths
and is not our situation. I'll pass on the tech support response when it
arrives.

Haven't yet checked if a problem with other functions, WHERE clauses
outside dataset option, formats other than user-defined etc etc.

Don

--
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