[SCIP] implementing a branching strategy

[James Cussens]

Dear SCIPers,

I would like to implement a branching strategy where at each node only a
subset of variables are considered as branching candidates. Which subset
this is will depend on the node in question (specifically which variables
are already fixed by the time we get to that node).

It seems to me that a potentially easy way of doing this is to update the
branching priorities of variables before the branching decision is made (I
want the current branching rule (eg relpscost) to choose which of my
candidates to branch on.)

But I'm not sure
1) if this is a reasonable way of implementing what I want to happen, and
2) if it is, where in my code to effect the branching priority updating.

I have a constraint handler (it's a "global" one - there is always a
constraint which is not satisfied until the entire problem is solved). One
option would seem to be to update the branching priorities in its ENFOLP
callback and declare SCIP_INFEASIBLE. But this seems a bit of hack.

Another possibility is to write an event handler, so that branching
priorities get updated when other variables get fixed.

Any advice / ideas?

James

-- 
James Cussens
Dept of Computer Science &
York Centre for Complex Systems Analysis
Room 326, The Hub, Deramore Lane            Tel    +44 (0)1904 325371
University of York                                        Fax  +44 (0)1904
500159
York YO10 5GE, UK                               http://www.cs.york.ac.uk/~jc
http://www.york.ac.uk/docs/disclaimer/email.htm
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