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There are two ways to check the array that I am aware of. LOOKUP and
%LOOKUP. The difference in performance appears to be a factor of 10.
Is that to be expected in your opinion? Can LOOKUP take 25 minutes to
run, and %LOOKUP take 4 minutes?
Depends on how you're using %LOOKUP. If you're using it on an array
that's been sorted, and has the "ASCEND" or "DESCEND" keyword coded on the
array definition, then you're doing a binary search lookup -- in which
case it doesn't surprise me one bit that %LOOKUP is 10 times faster than
LOOKUP.
The LOOKUP op-code (or %LOOKUP without ASCEND/DESCEND/SORT) is the same
thing (more or less) as looping through the array (with a DO or FOR loop)
and checking each array element to see if it matches. Much slower.
Of course, %LOOKUP won't compile to V4R2 anyway.
So, what say you? How to solve this pig of a performer?
If you want to continue to use an array, you could consider using the
bsearch() API (from the ILE C runtime library) it'll perform similarly to
the way %LOOKUP works.
Otherwise, consider at least trying using an indexed access method, such
as a database file w/CHAIN operation, or a user index. Although they
require disk access, which will slow it down, the algorithm for a keyed
lookup is much smarter than a linear "loop through all the elements" type
search operation. Of course, YMMV... Sometimes it'll be faster,
sometimes it wont.
HTH
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