[Scip] simple rounding and xor constraints

[James Cussens]

I have a problem where all the variables are binary and each variable 
participates in exactly one xor constraint. Each xor constraint states 
that exactly one of a certain collection of binary variables is true. 
(There is also another constraint implemented by my own constraint 
handler, but I don't think that's relevant).

I've noticed that simple rounding finds valid primal solutions. This 
seems a little odd since I think xor down- and up- locks each variable. 
My guess is that wholly integral solutions are being found during LP 
solving - does this seem right?

James

-- 
James Cussens	         ---- NEW CONTACT DETAILS ----
Dept of Computer Science &
York Centre for Complex Systems Analysis             jc at cs.york.ac.uk
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