[Coin-bcpdiscuss] Equal upper and global lower bound does not terminate the Branch-and-Bound algorithm.

[Anders Dohn Hansen]

Hi!

 

I am working on a branch-and-price algorithm in COIN/BCP, and I have a
couple of basic questions.

 

I have looked at the output from the Branch-and-Bound tree and it seems
that after finding an upper bound (an incumbent) which has the same
value as my global lower bound, it does not terminate right away, as it
should. It goes through all of the nodes that have been created so far
and runs one iteration for each node and thereafter that node is
fathomed. Since this iteration is not needed, is there anything I can do
to tell it to terminate right away when the upper and lower bound are
equal?

 

Another small fix I would like to have is to be able to add a constant
to my objective function. Is that accessible through some predefined
variable value or similar? I could of course always create a dummy
variable with the constant value and then fix that variable, but I
though that there may be a more correct way of doing that? I tried to
set the objective offset in the CLP-module, but that only changes my
solution value in the LP-solver. It seems that the tree manager
recalculates the objective value from the values of the variables.

 

Thank You

Anders Dohn

 

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