So, if someone compiles their COBOL program without optimization and tests 
it, then compiles it with optimization before putting it into production, 
does it need to be tested again?

Well, it's an excellent question Tom, but needs to be directed to people 
at sites that do that :-)

Pushed for an answer, I'd say "no". But, if you have.... and it ends up 
being the same asnwer as for ABO, which is why you've posed the question.

I on the other hand, when pushed for an answer would say "yes". Even if 
the optimizer in the compiler is 100% correct (not always the case), 
better optimization may make assumptions that the code in question does 
not happen to satisfy.

That is similar to the following:
As with ABO, it's not OPT I'm afraid of, it is the potential of bad 
I believe COBOL V5 stated that recompile would work for correct programs. 
I don't know if that statement is true or not, or what exactly is 
definitively meant by "correct", but I think that ABO's more conservative 
approach is expected to work even for programs that do not work upon 
recompile with COBOL V5. Of course once one error has been found in an 
implementation, most bets are off.

As to re-testing after recompile, if the resulting OBJ is the same, sure, 
no need. When can you expect that? Probably rarely, but that's only 
because there are often dates present in the output. So ignoring changes 
due to compile-date, changes in macros could affect things, so assume none 
of them. That brings you to something like application of a PTF. So are 
you compiling with the same PTF level of the compiler as before?

ouldn't it be great if the American Institute of Auditors (I've invented 
the name, but I'm sure there is at least one such organisation) and IBM 
got together and certified ABO. 
If by "certified" you basically mean "proved to be correct", how many 
realistic programs are ever provably correct (many non-realistic programs 
could be)? Surely a lot *are* correct, but could you prove it? I suspect 
that most software companies "warrant" (if an error is reported, it may be 
fixed) rather than "certify". 

Peter Relson
z/OS Core Technology Design

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