During a search partitions may be skipped to avoid turning the same stone twice
(See 15.1). As mentioned in
15.1, no record is kept of all partitions generated
so partitions are only skipped on theoretical grounds, that is, when it is presumed
that a partition has already been generated or will subsequently be generated. Information
on why partitions are skipped is sent to the output log during a search and a summary
is written in the Search Extent Box (18.1.1). The following messages may occur:
All are skipped, subset of ...
This message arises if searching up to a given size and if both conjunctive and
disjunctive forms are requested in the Search Extent Menu. because less complex
partitions in the hierarchy are covered by more complex ones. Specifically, the
p1,...,pq class with p1 > 1 and pi = 1 for all i = 2,...,q
is a subset of the class q,q,...,q, the number of q's
being p1. So
that, for example, the class 2,2 covers the class 2,1.
Another skipping message is:
x are skipped because Less than initial specified
upto
where x is the number of skipped partitions. This message arises in iterative mode
when substitution of the added attribute and Boolean simplification leads to a partition
that must have been covered on the initial iteration.
Another skipping message is:
n are skipped because Already covered; no added
attribute
This arises in iterative mode if the partition to be generated does not contain
the attribute created on the previous iteration. If it does not then there is no
point in generating the partition for it must already have been generated on the
initial iteration. SPAN calculates the number of such exclusions in advance of the
search, by the #( Excl) entry of the Search Extent Box (see
18.1.1).
[Back to table of contents]
