Date:         Fri, 9 Feb 2001 17:44:48 -0000
Reply-To:     sashole@bellsouth.net
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Paul Dorfman <paul_dorfman@HOTMAIL.COM>
Subject:      Re: Is Boolean logic faster?
Comments: To: dousk8@hotmail.com
Content-Type: text/plain; format=flowed

Nigel,

They compile into different things, but produce the same result. However, #2
does not involve multiplication. So it will be about 50% faster if the first
condition is true (so that both will have to be evaluated). If the first
condition is false, #2 will be more than 2 times faster. Finally, if you do
not care if TEST is zero or missing when it is not 1, this will be *still*
faster:

if num > 0 then if color='B' then test=1;

So it is not really the question about Boolean logic being faster, but
rather about the number of operations the computer has to perform and their
cost. A valid question about boolean vs non-boolean logic *could* be: Which
expression does SAS evaluate faster:  <if num=1> or <if num> ? If the actual
condition is true, then the answer is <if num=1>, because in this case SAS
only has to compare NUM with 1, i.e. perform at most one comparison, while
in order to evaluate <if num> SAS must ensure that NUM is greater than .Z
and not 0, i.e. perform at most 2 comparisons.

Kind regards,
==================
Paul M. Dorfman
Jacksonville, Fl
==================

>From: Nigel Tufnel <dousk8@HOTMAIL.COM>
>
>Is Boolean logic faster?  Does it matter?
>
>Which is faster
>
>    test = ((num > 0)*(color='B'));
>
>or
>
>    if num > 0 and color = 'B' then test=1; else test=0;
>
>Do both statements compile into the same thing?
>
>
>Please advise.
>Thanks,
>Nigel
>
>
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