[Coin-bcpdiscuss] Adding new cut when branching

[Francois Margot]

Klaus:

I have an example of branching on a constraint on my page

http://web.gsia.cmu.edu/fmargot/COIN/coin.html

in project number 4. This is exactly the branching you list below.
A short explanation of the method BCP_lp_branching_object() is given. 
To add different cuts in the sons, my understanding is that you actually 
add the same cuts to all the sons, but by playing with the upper and lower 
bounds on the cuts, you make some of them redundant in some of the sons.

Francois




On Tue, 31 Jan 2006 niklaus.eggenberg at epfl.ch wrote:

> Hi everybody,
>
> I am trying to branch on cuts rather than variables in my problem. No hudge
> problem so far, but I just realized that I didn't know how to include these new
> cuts... I know they must be added to vector "new_cuts" of object
> BCP_lp_branching_object in append_new_vars, and I suppose the coefficients have
> to be set in vars_to_cols?!
> But what I don't know is how to set a different cut for different children:
> suppose I want to branch on cut A_ij x_i = c (in the actual solution, c
> fractionnal) and set two new cuts
>
>         A_ij x_i <= floor(c)
>
> and      A_ij x_i >= ceil(c)
>
> Now how does this work? I am writing the function "append_branching_vars" but
> this is no help so far...
> I mean, I am not "really" generating a cut (only as it is implied by
> branching), so using generate_cut_in_lp() is not convinient.
>
>