<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
I am working with DIP (v0.8.2) and the MILPBlock example to test some<br>
ideas for automatic block detection and selection. But I have run into<br>
some problems. From previous messages on the mailing list I get the<br>
impression that my problems are caused by unboundedness.<br></blockquote><div><br><br>Please update to DIP trunk. There have been several changes and bug fixes since v0.8.2.<br><br><br><br><br><br> <br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
The problem can be illustrated with the unmodified MILPBlock example and<br>
the "atm_5_10_1" instance. If using the block file "atm_5_10_1.block"<br>
that comes with the example there is no problem. If instead another<br>
decomposition is chosen with the following block file, the problem arises:<br>
"0 30<br>
1 31<br>
2 82<br>
3 83<br>
4 134<br>
5 135<br>
6 186<br>
7 187<br>
8 238<br>
9 239"<br>
(If using this remember to switch to pair format).<br>
This decomposition relaxes the 10 column-disjoint knapsack constraint<br>
into 10 pricing problems. This results in the previously reported<br>
"Error: CBC IP solver 2nd status = 7" error.<br></blockquote><div><br><br>It looks to me like your subproblems should all be bounded. Is this error coming from a subproblem or from perhaps solving the IP as master? You are also using a very old version of DIP (and probably CBC) - so please upgrade and try again.<br>
<br>With trunk and with no artificial bounds, it does fail to solve Looking at the master problem, I can see why. The variables with no upper bound (master-only vars) do wind up entering the master problem with coefficients = infinity and CBC aborts because of numerical issues. I need to add extreme rays. It is on my ToDo list - see ticket: <a href="https://projects.coin-or.org/Dip/ticket/54">https://projects.coin-or.org/Dip/ticket/54</a><br>
<br>I will try to work on this soon-ish. In the meantime - using ColumnLB/UB options in MILPBlock should work.<br><br><br><br><br><br><br><br><br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
If I use artificial column bounds as suggested I instead get (what I'm<br>
guessing is) precision problems from the large magnitude bounds:<br>
<br>
COIN Exception [ Primal and Dual Master Obj Not Matching. ] at<br>
../../../Dip/src/DecompAlgo.cpp:L2612 in DecompAlgo::checkBlocksColumns"<br>
(the above was obtained with the bounds "ColumnLB = -1.0" and "ColumnUB<br>
= 3500")<br></blockquote><div><br><br>Using trunk, this seems to solve fine - although I do get some warnings about slight row violations (I'll look into that). Trying upgrading.<br><br>Thanks,<br>Matt<br><br><br>
</div></div><br>