Re: RPG IV Performance

On Fri, 19 Jan 2001 Lisa.Abney@universalflavors.com wrote:

> Hi all!  I've just heard some rather negative performance things on RPG IV, 
>and
> wonder if anyone can give me some feedback on how true this might be.
> 
> We're working with a consulting company who is doing some performance
> analysis on some of our programs.  They seem very knowledgeable, and I
> have a lot of confidence in what they've done up until now.  However,
> today they were showing us a mock-up of a trigger program they want to
> use.  As they explained it, this trigger program will be constantly
> running in the background for every user on the system to monitor
> changes to two files, and will feed data to a dataque. The program
> they showed me was written in RPGIII, and I made my usual request to
> an outside contractor that this be done in RPGIV.  His response was
> "Sure, if you want the program size to be 5 - 10 times the size of an
> RPGIII program." 

Correct, RPG IV programs are generally larger than RPG III programs.   I
believe that this has to do with the difference between ILE and OPM
compiles.    I don't buy the "5-10" times the size story, though.  That
seems excessive.  

But, perhaps he's storing debug info in the RPG IV program...  which makes
it larger...   you can't do that in RPG III, but you can in RPG IV.

At any rate, most people aren't worried about a few extra kilobytes of
disk space.  Systems today tend to ship with at least 8 gigabytes of disk
space...


> When I asked him to explain that, he only said that,
> in his experience, this is always true, and that it would have a very
> negative performance. 

No, thats not true.   A comparable RPG III and RPG IV program will perform
about the same.   A well-written RPG IV program will easily outperform an
RPG III program because you can't use pointers in RPG III.

A poorly written RPG IV program (for example, using ACTGRP(*NEW) on a
trigger program) would be slower, of course.

> I even mentioned removing observability (not that I really understand
> what that means, but I just read something the other day about that
> being a way to reduce program size!), and he said that might move it
> down to 3 - 5 times the size of an equivalent RPGIII program.  The
> program will only be about 50 - 100 lines of code.

I've got a 139 line trigger program, written in RPG IV, it's 76k.  I dont
have any triggers written in RPG III, but a 133 line RPG III program that
I have is 54k.  

Even if I recompile my 139 RPG IV program with DBGVIEW(*LIST) (which
includes all of the source code for the program in addition to the 
compiled code) it's only 99k.  Still less than twice the RPG III size.

>
> Can someone explain if this is true, and, if so, why?  And, if true,
> what does this really mean from a performance standpoint?
> 

Again, a well written, well designed program by someone who understands
ILE and RPG IV will easily outperform an RPG III program.  Easily.

So what does this mean? It means your consultant doesn't want to learn 
RPG IV.  If he's really worried about the 20k of disk space, he should go
back to programming a VIC-20 where it was important. :)


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