Re: A question about Dominators

"Robert Sherry" <rsherry8@home.com>schreibt:
>The basic idea of the first approach is that node a
>dominates node b if and only if a=b or a is the unique immediate predecessor
>of b or b has more then one immediate predecessor and for all immediate
>predecessors c of b, c is not equal to a and a dominates c.


IMO it's a matter of taste/convention, whether a node dominates itself
(a=b). But I definitely see no reason, why the dominator cannot be
one of multiple immediate predecessors.


In a graph with the edges (a,b), (a,c), (b,c) node a dominates both
nodes b and c.


So the idea should read:


Node a dominates node b if a=b, or for all immediate predecessors c of b, a
dominates c.


Now the case a=b also makes sense, since when node a is an immediate
predecessor of b, then node a dominates itself (as predecessor c of b). It's
not required that a<>c, and a single predecessor is only a special case of
multiple predecessors.


BTW, do you have an equivalent definition or idea for post-dominators?


DoDi

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