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<div class="moz-cite-prefix">Hi James,<br>
<br>
If cutting planes are added to the master problem, the
corresponding dual variables need to be considered in the pricing
problem. If you don't consider these dual variables, it will make
the pricing problem invalid. Usually the structure of the pricing
problem changes when cuts that are formulated with master
variables are added, i.e., additional variables or constraints
have to be added to the subproblem. How the subproblem is changed
depends on the type of the added cut. This is why separation is
disabled in the bin packing example.<br>
<br>
Alternatively, one can add cuts from the original problem in the
context of Dantzig-Wolfe reformulation; these cuts only change the
objective function of the subproblem. But in the bin packing
problem the pricing problems are aggregated, which is why this
would reintroduce a lot of symmetry and pricing problems have to
be disaggregated again.<br>
<br>
For more details, you can have a look at the following paper:<br>
<a class="moz-txt-link-freetext" href="https://doi.org/10.1002/net.20471">https://doi.org/10.1002/net.20471</a><br>
<br>
Best regards,<br>
Jonas<br>
<br>
On 09/11/2018 01:53 PM, James Cussens wrote:<br>
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<div dir="ltr">I notice that in the binpacking branch-and-price
example, that all separators are turned off. My guess is that
this is to avoid the risk of a separator generating an
inequality that (1) becomes invalid once a new variable is added
by the pricer and (2) where it be too complex to add the new
variable to recover validity.
<div><br>
</div>
<div>Is this correct, or is there some other reason for this?</div>
<div><br>
</div>
<div>Thanks,</div>
<div><br>
</div>
<div>James<br>
-- <br>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">James Cussens<br>
Dept of Computer Science &<br>
York Centre for Complex Systems Analysis<br>
Room 326, The Hub, Deramore Lane Tel +44
(0)1904 325371<br>
University of York
Fax +44 (0)1904 500159<br>
York YO10 5GE, UK <a
href="http://www.cs.york.ac.uk/%7Ejc" target="_blank"
moz-do-not-send="true">http://www.cs.york.ac.uk/~jc</a><br>
<a href="http://www.york.ac.uk/docs/disclaimer/email.htm"
target="_blank" moz-do-not-send="true">http://www.york.ac.uk/docs/disclaimer/email.htm</a></div>
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