RE: SCAN vs %scan

["Morgan, Paul" <Paul.Morgan@xxxxxxxxxxx>]

Yeah but it was in COBOL years ago.

There's some overhead encoding your search string but you make that up executing the search.  A nice attribute is this algorithm is faster with longer strings.  But if you're only searching for one or two characters or the text you are probing is short then a linear search like SCAN or %Scan is better. 

There's enough search algorithms to fill a book (or half a book) so check out Knuth's "Art of Computer Programming, Volume 3: Sorting and Searching".

Paul Morgan

Principal Programmer Analyst
IT Supply Chain/Replenishment

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Rory Hewitt
Sent: Monday, January 09, 2012 3:07 PM
To: RPG programming on the IBM i / System i
Subject: Re: SCAN vs %scan

Paul,

Nice find! Have you tried implementing this?

Rory

On Mon, Jan 9, 2012 at 11:49 AM, Morgan, Paul <Paul.Morgan@xxxxxxxxxxx>wrote:

> Have you considered coding a faster string search algorithm like
> Boyer-Moore?
>
> http://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string_search_algorithm
>
> Paul Morgan
>
> Principal Programmer Analyst
> IT Supply Chain/Replenishment
>
> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
> On Behalf Of sjl
> Sent: Monday, January 09, 2012 2:12 PM
> To: rpg400-l@xxxxxxxxxxxx
> Subject: SCAN vs %scan
>
> has anyone benchmarked speed comparison of using SCAN versus %SCAN?
>
> I inherited and am maintaining a fixed-format RPGIV program which uses SCAN
> to scan strings for certain values (hundreds of occurences of the SCAN
> opcode), and I am wondering if I can get any kind of performance
> improvement
> if I change them to use %scan instead.
>
> - sjl
>
>
>
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