[gecode-users] exact behaviour of different IntValBranch

[Guido Tack]

Christian Schulte wrote:
> Let's take INT_VAL_MED as an example with x as selected variable and n the
> median. Then you create a choice (x <= n) v (x > n).

That's not quite correct, INT_VAL_MED creates (x==n) v (x != n) just like INT_VAL_{MIN,MAX}.  And the median is computed again for each new node.

The splitting cases are INT_SPLIT_MIN, which does (x <= n) v (x > n) for n = (x.min()+x.max())/2, or INT_SPLIT_MAX where the two choices are swapped.  That's why the documentation talks about values (plural) here: The branching does not assign a single value to the variable, but splits the domain (of course, when the domain had size 2, the result of the split is a single value).

A good way to find out what the branchings do exactly is to have a look at the search tree in Gist.

Cheers,
	Guido

-- 
Guido Tack, http://people.cs.kuleuven.be/~guido.tack/