[Scip] branching

[Alessia Violin]

Hello,

I have some questions/doubts about the branching. I have implemented my 
own branching together with the pricing, in the form of a constraint 
handler, as I don't have any variable to be integer but a constraint 
(equal to the sum of variables with some parameters) to be integer in 
the optimal solution. To do so in the constraint handler I am checking 
if this sum is integer, if yes I end up with *result = SCIP_FEASIBLE, if 
not I create two nodes, add constraints to them and end with *result = 
SCIP_BRANCHED.

The code is working and finding the correct solution, but I was 
wondering if I should also modify some bounds in this process or if 
everything is done automatically by scip? For instance when I found an 
integer solution, should I manually modify the primal or the cut off 
bound? (all of this to eventually speed up the solving).

The second thing is about the estimate value for a node. I printed out 
the node selector rule used by scip, and I got "best estimate", so I 
think it is using this value to choose nodes in the tree, right? In the 
constraint handler when I create the two nodes I can give to each of 
them an estimate value, within the fourth parameter of the function 
SCIPcreateChild. I would like to modify this value for each node after 
solving it with the pricing, to have a more accurate value. Is there a 
way to do this, as a function "set node estimate" or similar? I was not 
able to find it in the documentation.

Finally, the third parameter of SCIPcreateChild is a "node selection 
priority of the node", for now I have set it to 1.0 for both nodes I 
create in the branching, but I was wondering which is the role of this 
parameter in the branching?

Thanks a lot for any help,

best,

Alessia


-- 
Alessia Violin
Service Graphes et Optimisation Mathématique (G.O.M.)
Université Libre de Bruxelles
C.P. 210/01
Boulevard du Triomphe
B-1050 BRUXELLES
Tel: 02 650 58 80 - Fax: 02 650 59 70
Email: aviolin at ulb.ac.be
Webpage: http://homepages.ulb.ac.be/~aviolin/