I'm going to try to walk a delicate line here. I don't want to offend the fine 
folks at IBM, and IBM's compiler people are a bright, bright bunch of folks up 
in Toronto. They know more about compilers than I ever will. But, that said ...

I agree with you on testing. A recompile of unedited source code demands a full 
regression test IMHO. Who knows what might have changed: a PTF, an environment 
variable, you only thought it was unedited (you forgot about Fred) -- whatever. 
Heck, on our product, we do a partial regression test after a re-link of 
unchanged object code "just to make sure."

So I raise my eyebrows at the assertion that since the ABO is just a massage of 
the existing compiled object code no re-testing is necessary. I don't deny it; 
I just raise my eyebrows: IBM's compiler team knows a lot more about this stuff 
than I do.

Yes, "we can't find the source code" or "we found 17 versions of the source 
code and we don't know which one is in production" is apparently a reality -- a 
very scary reality IMHO, but certainly a justification for ABO.


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf 
Of Karl S Huf
Sent: Wednesday, October 12, 2016 3:49 PM
Subject: Re: ABO Automatic Binary Optimizer

In our experience the need for PDSE datasets was far from the only difficulty 
in migrating to COBOL V5 (and that really wasn't the hard part).  Many compiles 
take drastically more CPU time as well as require more region.  While this is 
documented we were stunned by the orders of magnitude.  Compiles that had 
previously taken single digit CPU seconds suddenly needed minutes (this is on a 
z13).  Similarly where a 4MB Region default had been adequate those compiles 
routinely failed; we were directed to specify 200MB but found even that 
frequently failed and threw up our hands and told everybody to use REGION=0 
(personal peeve of mine).  We also did find some incompatibilities for which we 
opened up PMR's and received APAR's.

Within the context of the thread topic, ABO . . . I discussed this quite a bit 
with my account team.  Our developers are required to do regression testing on 
their changes - even if it is just recompiling
with no source code changes.    They initially argued (well, not
initially, it went on way too long) that there's no need to do such testing 
when using ABO.  Technically they may be right; technically one probably 
shouldn't have to do complete regression testing when recompiling the same 
source.  None of that makes any difference if the stated requirement in the 
development standards they have to follow says they DO have to do that testing. 
 Knowing that, then, they would be similarly required to do that testing for an 
ABO optimized module we questioned the benefit of licensing another product to 
do the same thing the compiler can do.  Now, if there's a substantial amount of 
executing COBOL code that consumes a fair amount of resources AND the source is 
missing/unavailable then maybe ABO is in play - but that's not our situation.

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