Re: Pointer vs. BIF performance (was: Getting into pointers)

Actually I didn't even notice that David was using %trim rather than %trimr. %trim won't work (or at least won't do what he described as being his intent) if there are leading blanks in SRCDATA.

Bruce

----- Original Message ----- From: "Charles Wilt" <charles.wilt@xxxxxxxxx>
To: "RPG programming on the IBM i / System i" <rpg400-l@xxxxxxxxxxxx>
Sent: Wednesday, August 12, 2009 2:03 PM
Subject: Re: Pointer vs. BIF performance (was: Getting into pointers)


Bruce and Lim both suggest using trimr() instead of trim()....however
I'd be willing to bet that David want trim() to take care of control
characters on both the left & right.

In any event, if you're talking about performance, I'd do this:
charPtr = %addr(SRCDATA);
strLen = %len(%trimr(SRCDATA));
for p = 0 to strLen;
if char < x'40';
char = *blank;
endif;
charPtr += 1;
endfor;

Since according to the manual:
"Note: If the FOR loop is performed n times, the limit value is
evaluated n+1 times and the increment value is evaluated n times. This
can be important if the limit value or increment value is complex and
time-consuming to evaluate, or if the limit value or increment value
contains calls to subprocedures with side-effects. If multiple
evaluation of the limit or increment is not desired, calculate the
values in temporaries before the FOR loop and use the temporaries in
the FOR loop."


HTH,
Charles
On Wed, Aug 12, 2009 at 2:38 PM, bvining<bvining@xxxxxxxxxxxxxxx> wrote:

I would expect the pointer implementation to be a bit faster than substring
operations with a variable (unless Barbara and/or wcode has really gotten
into some optimization work). I would have used the pointer approach (for
what that's worth) with a slight change:

charPtr = %addr(SRCDATA);
for p = 0 to %len(%trimr(SRCDATA));
if char < x'40';
char = *blank;
endif;
charPtr += 1;
endfor;

Bruce

----- Original Message -----
From: "David Gibbs" <david@xxxxxxxxxxxx>
To: "RPG programming on the IBM i / System i" <rpg400-l@xxxxxxxxxxxx>
Sent: Wednesday, August 12, 2009 9:42 AM
Subject: Pointer vs. BIF performance (was: Getting into pointers)

This question is mostly out of idle curiosity ...

I've got a simple routine that is designed to replace any 5250 control
characters in a RPG source file with blank.

for p = 1 to %len(%trim(SRCDATA));
if %subst(SRCDATA:p:1) < x'40';
%subst(SRCDATA:p:1) = *blank;
endif;
endfor;

Would there be any performance benefit if I used a pointer to update the
field?

D charPtr S *
D char S 1A based(charPtr)

.
.
.

for p = 0 to %len(%trim(SRCDATA));
charPtr = %addr(SRCDATA)+p;
if char < x'40';
char = *blank;
endif;
endfor;

Thanks!

david

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