Re: How can I Improve this procedure...

Scott,
Thanks for the suggestions. I have a few more questions based on ur
suggestions, quoted in your reply.


On 4/19/06, Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx> wrote:
>
>
> > How can I improve this procedure for performance? I am a little worried
> > about how the ReasonDS is declared.
> > Basically I need an Array of the Datastructure that the procedure can
> > return. I also need to be able to look up this array with @RsnCode as
> the
> > key.
>
> The best way to improve performance is to pass the data structure as a
> parameter instead of as a return value.  The return value is much less
> efficient, and I personally would never use it for anything larger than 30
> bytes (or so) if performance is a concern.


  >>> can you elaborate on this? I keep hearing it very often but did not
find much explantation as to why?
        Is this the case with procedures too? Also is it any different if
the procedure is in a service program?
        Is it not just a pointer that is returned? Any pointers to books/IBM
resources on this topic will be helpful too.


> * Array of Data structures to hold reason code details
> > D  ReasonDS       DS          5400
> > D   @RsnCode                     2A   Dim(200)
> > D   @Charge                      9  2 Dim(200)
> > D   @Weight                      9  0 Dim(200)
> > D   @Units                       7  0 Dim(200)
>
> This isn't an array of data structures.  It's a data structure that
> contains 4 arrays, each array is independent of the others.  I also don't
> understand why you've hardcoded the data structure to be 5400 bytes long
> when it actually only needs 3200 bytes of memory.  I know that 2200 bytes
> isn't a big deal, but why waste it if it brings you no benefit at all?
>
> You probably meant to do this:
>
>       D                 DS
>       D ReasonDS                            dim(200)
>       D  @RsnCode                      2A   overlay(ReasonDS:1)
>       D  @Charge                       9P 2 overlay(ReasonDS:*NEXT)
>       D  @Weight                       9P 0 overlay(ReasonDS:*NEXT)
>       D  @Units                        7P 0 overlay(ReasonDS:*NEXT)
>
> In this case, "ReasonDS" is an array of 16A DIM(200).  The other fields
> overlay positions in that array, so @RsnCode is an array that always
> overlays positions 1-2 of ReasonDS.  @Charge is an array that overlays
> positions 3-7 of ReasonDS, etc.


>>> In this case does RPG allow  %lookup('XX': @RsnCode)  ?  I guess not as
@RsnCode is not an array.
       Anyway I have to try it out. If it works then I will be perplexed as
it is not obvious.

Alternately, you could code it as follows:
>
>       D ReasonDS        ds                  qualified dim(200)
>       D  @RsnCode                      2A
>       D  @Charge                       9P 2
>       D  @Weight                       9P 0
>       D  @Units                        7P 0
>
> In this case, it actually *is* an array of data structures.  You have one
> DS with 4 subfields, and 200 copies of that DS.  The only problem with
> this technique is that RPG won't let you use BIFs like %LOOKUP, or
> op-codes like SORTA on the array, which some people find to be a
> disadvantage.  Personally, I don't mind coding my own functions to
> replace %LOOKUP and SORTA, so it doesn't bother me.


>>> This is exactly what I meant to do, but for the lack of %lookup support.
Would it be possible to write a generic procedure, you can pass an array
(could be an array of datastructure) that could look up this array... I am
just thinking loud here.


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