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My first thought was the same as Bruce's - that an individual character loop would be by far the fastest approach.

You always have to remember that no magic is involved and that in order to implement %Xlate or %ScanRpl RPG still has to implement a character at a time loop unless there is can underlying system function that can perform the task - and even then that just moves that loop down closer to the hardware.

But so many in this thread seemed convinced that the BIF approach would be faster I decided to test and compare Francois' code with a simple loop.

The time difference is dramatic. The single char loop is orders of magnitude faster.

Run the following and see for yourself. On my system I get the following:

DSPLY Xlate took: 1094
DSPLY Loop took: 59

And those results are consistent.

Here's the code I used - if you spot a bug let me know.


dcl-ds str;
strChar char(1) Dim(1000);

dcl-s blank64 char(64) inz;
dcl-s i int(5);
dcl-s startTime timestamp;
dcl-s endTime timestamp;

startTime = %timestamp();

for i = 1 to %elem(strChar);

str = X'12' + 'some string' +X'350A13';
str = %Xlate(X'000102030405060708090A0B0C0D0E0F+
: blank64

endTime = %timestamp();

Dsply ( 'Xlate took: ' + %char(%diff( endTime : startTime : *MS )));

startTime = %timestamp();

for i = 1 to %elem(strChar);

if strChar(i) < X'40';
strChar(i) = *Blank;


endTime = %timestamp();

Dsply ( 'Loop took: ' + %char(%diff( endTime : startTime : *MS )));

*InLr = *On;

On Nov 18, 2021, at 6:45 PM, Francois Lavoie <Francois.Lavoie@xxxxxxxxxxxxxxxxxxxx> wrote:

Here's the code I tested: ultra fast and ultra compact. A 1-liner beats any slow do 1-char at a time multi-line of code loop
dcl-s str char(1000);

str=X'12'+'some string'+X'350A13';
:' '+
' '

make sure the 2nd parm of the Xlate bif has exactly 64 blanks

-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Bruce Vining
Sent: Thursday, November 18, 2021 18:33
To: RPG programming on IBM i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: [EXTERNAL] Re: Remove unprintable chars

Caution: This email originates from outside of Fresche | Attention: Ce message provient de l'extérieur de Fresche

I'm going to exit this thread as I'm clearly missing something, but do believe that the explicit loop looking for < blank (as proposed by Alan) is the best performer. I really hope that Barbara notices this thread and joins in as I'm always open to education from her :)

To me Xlate (and I agree with Scott on Xlating to x'40' rather than x'39'
or some such followed by a ScanRpl) is "somewhere" (I don't know if it might be an implicit RPG compiler generated lookup or a MI instruction as I haven't checked MI in a long, long time) having to look up the current byte being processed and having to search to see if it is in the Xlate from string in order to replace it with the Xlate to string, which certainly suggests more machine processing to me. Doing a direct loop on < blank eliminates this additional processing of specific from values. Please note that I'm looking at this strictly from a system performance (cycles) point of view.

I also agree with Scott on < '40' might be a problem in some environments and I'm thinking DBCS shift controls in particular (though there is nothing in this thread suggesting DBCS needs).

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