[SCIP] question on branching

[James Cussens]

Dear SCIPers,

I have a problem which includes a particular integer variable (call it x)
which I always want to branch on even if it is integral and other
binary/integer variables are fractional - I would only branch on any other
variable if x were fixed. As for how to branch on this variable, the
BRANCHEXECPS approach described here:
http://scip.zib.de/doc/html/BRANCH.php
is exactly what I am looking for.

Giving this x variable maximal branching priority does not work, since if
(as is normally the case) there is an LP solution with some fractional
variables not including my x, then x will not be branched on.

So it looks like I need to write my own (simple) branching rule where
the BRANCHEXECLP callback grabs branching candidates
using SCIPgetPseudoBranchCands rather than SCIPgetLPBranchCands. However,
looking at the code in branch.c it appears that SCIPgetPseudoBranchCands
returns branching candidates without taking variable priority into account.

Is that correct?

Best wishes,

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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