Re: To OPTIMIZE or not to OPTIMIZE...

["Joe Sam Shirah" <jshirah@xxxxxxxxxxxxx>]

    Hi Adam,

    To add to the previous answer, as of V5R2, except in cases where the
priority is the fastest possible startup time, the recommendation is to no
longer use CRTJVAPGM.  Rather than leave my statement as an edict from above
( or sideways or below  ;-) ), check out the info at:

"V5R3 Performance Capabilities Reference - May/July/Aug/Oct 2004 Edition"

Chapter 7

http://publib.boulder.ibm.com/iseries/v5r3/ic2924/books/sc410607.pdf

    There are also earlier editions at:

"Performance Management"

http://www-1.ibm.com/servers/eserver/iseries/perfmgmt/resource.htm

    And see the articles:

"With V5R2, the JIT Compiler Comes of Age"

http://www.eservercomputing.com/iseries/archives/index.asp?a=1&id=320


"Why is My Java Application Running So Slowly?"

http://www.eservercomputing.com/iseries/archives/index.asp?a=1&id=868


    As to the optimization level for CRTJVAPGM, I always used 30.  That was
based on some admittedly old info ( that I never revisited ) that you could
encounter problems with level 40 optimizations.

    While it seems intuitively obvious that loading a class directly is
faster than from a jar,

A:  It depends.

and

B:  You're looking at ( normally ) a one-time hit that's pretty small in and
of itself, and certainly in the overall scheme of things.  If that weren't
the case, there probably wouldn't be a runtime jar or JT400.jar and so on.
Jars allow management and tracking.capabilities generally judged more
important than the possible runtime hits.


                                                         Joe Sam

Joe Sam Shirah -        http://www.conceptgo.com
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----- Original Message ----- 
From: "Adam Stotts" <adamstotts@xxxxxxxxxxxx>
To: <java400-l@xxxxxxxxxxxx>
Sent: Monday, March 14, 2005 5:05 PM
Subject: To OPTIMIZE or not to OPTIMIZE...


>
> Survey poll: Of those of you who read this, have you optimized your Java
> code with CRTJVAPGM, and if so, which option - *INTERPRET?  40? I am
> hearing conflicting opinions on this vital topic. Secondary question: do
> you load classes from JAR files, or does your classpath only include
> Java class files?
>
> Thanks,
>
> Adam.
>