[Cbc] confused about depth

[John Forrest]

James,

As you may have gathered by now SOS is not as solid as it should be.

If the branching rules are really bad and if there were 20 members in 
each S1 set then you could get to a depth of 270*19 (or maybe 18).  
However from what I remember there are not that many members in each set.

If you send me the model (and maybe your driver), I will see what the 
problem is and try to come up with a better branching strategy and a way 
to implement it cleanly.

John
On 14/11/2018 00:47, James Howey wrote:
>
> I have a model that occasionally gets lost in the weeds.
>
> Cbc0010I After 6200 nodes, 4814 on tree, 1e+50 best solution, best 
> possible 0 (97.67 seconds)
>
> Cbc0020I Exiting on maximum time
>
> Cbc0005I Partial search - best objective 1e+50 (best possible 0), took 
> 549614 iterations and 6236 nodes (100.02 seconds)
>
> Cbc0035I Maximum depth 4816, 0 variables fixed on reduced cost
>
> My confusion stems from the reported maximum depth of 4816. I have 
> only 270 (sos) objects in the model.
>
> It would seem that by the time I reach 270 I could judge this node 
> integer feasible or not, and continue in shallower depths.
>
> Is this behavior by design, and if, as I suspect, it is, are there 
> situations where this strategy is effective? Maybe even my situation?
>
> Additional info: In my situation, there is an order to the objects 
> that will reliably give you an infeasible/integer solution judgment by 
> the time you reach 270. I have prioritized the objects in this order 
> and turned off strong branching.
>
> What would happen if I hacked the branch decision logic to just  never 
> split the last level? Is branch logic where I will be spending my time 
> in the future?
>
> Thanks for any light you can shed.
>
> jkh
>
>
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