Thank you very much for this. In my models using the domain propagation
in distinct does seem to improve the run-time substantially so the extra
work does pay off in my case.
I can see this option in the doc now I look for it!
Neill.
On 9/20/2015 3:58 PM, Guido Tack wrote:
Hi,
there are several different propagators for the distinct constraint in Gecode,
and the default one is quite weak and won’t detect these cases. If you post
distinct with ICL_DOM as the third argument you will see the behaviour you
expect (but you’re right, 6M variables will be stretching it - the complexity
of propagating distinct with ICL_DOM is quadratic).
Cheers,
Guido
On 21 Sep 2015, at 8:55 am, Neill Clift <neillcl...@live.com> wrote:
Hi,
I have been playing with gecode for a few days and having a lot of fun.
My overall goal is to solve a large problem that has close to 6 million values
that must be distinct. So kind of like this:
IntVarArray b(*this, 5784689, 0, 5784688);
distinct(*this, b);
Notice that the b's are constrained to be essentially a permutation of
0...5784688.
These b values are generated by sets of linear equations derived from a
directed acyclic multi-graph.
I expect district is a killer. I don't have a hope of attacking this big
problem I think. So I am playing with smaller problems. I see gecode searching
spaces like this:
So 6 b's that are distinct values with a range of 0..5:
b{[2..5], [1..4], [1..4], [1..4], [0..3], [0..3]} this should really be b{[5],
[1..4], [1..4], [1..4], [0..3], [0..3]}. Maybe I am not using the right way to
express what I want and the range and distinct aren't cooperating enough?
b{[2..4], [1..4], [1..4], [1..4], [0..3], [0..3]} no 5 at all so this should
fail.
More complex case:
b{5, [3..4], [3..4], [2..4], [0..3], [0..3]} should be b{5, [3..4], [3..4],
[2], [0..1], [0..1]}.
Computationally I guess it might be very expensive to discover these things.
Even if you do discover these things I guess it might be it doesn't help that
much.
Thanks.
Neill.
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