[Coin-bcpdiscuss] Variable LB fixed to 1 by BCP
matteo.salani at epfl.ch
Wed May 9 11:26:55 EDT 2007
I've encountered a behavior of BCP that sounds strange to me...
I'm solving a set covering like problem with BCP.
At iteration 12 the lower bound of one variable becomes 1 unless the
column generation process is not over (I've in total 149 iterations)
it sounds very strange to me that such fixing can occur at this point.
to see that I've added in the derived method
App_lp::modify_lp_parameters which is called *before* the LP is solved
the following piece of code to write the current LP to a file:
sprintf( fname, "lp-out%d", count++);
lp->writeLp( fname, "lp");
count is just a static counter to have a file per iteration.
I've checked that in all the code I do not modify any variable bound.
What else should I check?
Is BCP acting on variables' LBs?
Am I right when I say that reduced cost fixing could act only on
variables' upper bounds?
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