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<font size="-1">Hi Haroldo</font>,<br>
<br>
<small>Thanks for your reply.<br>
Could you email me when you will fix it?<br>
<br>
For the moment, i have another problem with (i suppose) mipstart.<br>
Before sending it to you, i found the lowest possible constraint file having this problem. So, it is not a "real" case, just a test case.<br>
<br>
1/<br>
I have a constraint file t.lp that i want to compile with mipstart.<br>
If i resolve it with coin, the solution file, t.sol, is ok.<br>
<i>bin/cbc t.lp branch printingOptions normal solution t.sol</i><br>
<br>
2/<br>
So, before doing it, i create a "trivial" constraint file, t_t.lp which is a more severe version of t.lp problem. The solution provided is t_t.sol.<br>
The solution file is also ok.<br>
<i>bin/cbc t_t.lp branch printingOptions normal solution t_t.sol</i><br>
<i><br>
3/<br>
</i>Now i want to solve the t.lp problem with t_t.sol file as mipstart:<br>
<i>bin/cbc t.lp mipstart t_t.sol preprocess off branch printingOptions normal solution t_mips.sol<br>
<br>
</i>The solver appears to be ok and claims that the mipstart solution is correct:<br>
<br>
<i>Welcome to the CBC MILP Solver </i><i><br>
</i><i>Version: Trunk (unstable) </i><i><br>
</i><i>Build Date: Feb 11 2015 </i><i><br>
</i><i>Revision Number: 2136 </i><i><br>
</i><i><br>
</i><i>command line - bin/cbc t.lp mipstart t_t.sol preprocess off branch printingOptions normal solution t_mips.sol (default strategy 1)</i><i><br>
</i><i>will open mipstart file ./t_t.sol.</i><i><br>
</i><i>mipstart values read for 63 variables.</i><i><br>
</i><i>Option for preprocess changed from sos to off</i><i><br>
</i><i>Continuous objective value is 4308.59 - 0.00 seconds</i><i><br>
</i><b><i>Cbc0045I mipstart provided solution with cost 4311.51</i></b><i><br>
</i><i>Cbc0006I The LP relaxation is infeasible or too expensive</i><i><br>
</i><i>Cuts at root node changed objective from 1.79769e+308 to -1.79769e+308</i><i><br>
</i><i>Probing was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>Gomory was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>Knapsack was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>Clique was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>MixedIntegerRounding2 was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>FlowCover was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i>TwoMirCuts was tried 0 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)</i><i><br>
</i><i><br>
</i><i>Result - Optimal solution found</i><i><br>
</i><i><br>
</i><i>Objective value: 4311.51200000</i><i><br>
</i><i>Enumerated nodes: 0</i><i><br>
</i><i>Total iterations: 1</i><i><br>
</i><i>Time (CPU seconds): 0.00</i><i><br>
</i><i>Time (Wallclock seconds): 0.00</i><i><br>
</i><i><br>
</i><i>Total time (CPU seconds): 0.00 (Wallclock seconds): 0.03</i></small><br>
<br>
<small>Unfortunately, the t_mips.sol file contains non-integer values.<br>
So, what's wrong with this test case?<br>
[All the files are attached]<br>
<br>
Cheers,<br>
<br>
Yves<br>
</small><br>
<br>
<div class="moz-cite-prefix">Le 02/19/2015 02:08 AM, Haroldo Gambini Santos a écrit :<br>
</div>
<blockquote cite="mid:54E53773.9000708@gmail.com" type="cite">Hi Yves and John,<br>
<br>
I checked the execution here, the problem is:<br>
<br>
<big><b><font size="-1"><big><i>Cgl0004I processed model has 0 rows, 0 columns (0 integer (0 of which binary)) and 0 elements</i></big></font></b><b><br>
</b></big><br>
The pre-processed problem is empty, so, in this case, there is no need of MIPStart because the will be no branch and bound anyway.<br>
<br>
John: I commited some fixes (in trunk) for MIPStart, but not for this case, where the fix would be to give up of MIPStart if the pre-processed problem is empty. Could you please check where we decide to skip mipstart ?<br>
<br>
Cheers<br>
<br>
<br>
<div class="moz-cite-prefix">On 17-02-2015 12:40, Yves Touchard wrote:<br>
</div>
<blockquote cite="mid:54E352EA.8040206@dxo.com" type="cite"><font size="-1">Haroldo,<br>
<br>
Another behavior that i don't understand.<br>
You will find the basic tested constraints file attached.<br>
<br>
First, i generate an integer solution file:<br>
<i>bin/cbc test.lp branch printingOptions integer solution int.sol</i><br>
<br>
Then i re-compile it with the solution file as a mipstart:<br>
<i>bin/cbc test.lp mipstart int.sol branch printingOptions integer </i><i>normal</i><i> test.sol</i><br>
<br>
The solver claims:<br>
<br>
<i>will open mipstart file ./int.sol.</i><i><br>
</i><i>mipstart values read for 5 variables.</i><i><br>
</i><i>Continuous objective value is 394.427 - 0.00 seconds</i><i><br>
</i><i>Cgl0004I processed model has 0 rows, 0 columns (0 integer (0 of which binary)) and 0 elements</i><i><br>
</i><i>Cbc0045I Warning:<b> MIPstart solution is not valid, ignoring it</b>.</i><i><br>
</i><i>Cbc3007W <b>No integer variables </b>- nothing to do</i><br>
</font><br>
<font size="-1"><font size="-1">Then, the test.sol seems to be buggy.<br>
<br>
Maybe, i am wrong but i cannot see what is wrong.<br>
<br>
</font>Cheers,<br>
<br>
Yves<br>
<br>
</font>
<div class="moz-cite-prefix">Le 02/17/2015 12:49 PM, Haroldo Gambini Santos a écrit :<br>
</div>
<blockquote cite="mid:54E32AB2.307@gmail.com" type="cite">Hi Yves,<br>
<br>
Could you please send me your problem file (LP or MPS) ?<br>
<br>
Since there are other reports of problems with MIPStart maybe there is some bug.<br>
<br>
Cheers<br>
<br>
<div class="moz-cite-prefix">On 17-02-2015 09:27, Yves Touchard wrote:<br>
</div>
<blockquote cite="mid:54E325A7.5090906@dxo.com" type="cite"><font size="-1">Hello,<br>
<br>
Just a simple question (surely stupid...).<br>
The solver generates an integer solution file from a very basic constraint file.<br>
Then I re-compile the same constraint file with the previous solution file as mipsart argument. And cbc claims:<br>
<br>
[...]<br>
<i>will open mipstart file ./bug_gen.sol.</i><i><br>
</i><i>mipstart values read for 3 variables.</i><i><br>
[...]<br>
</i><big><i><small>Cbc0045I Warning: mipstart values could not be used to build a solution.</small><br>
<small>Cbc0045I Trying just fixing integer variables.<br>
Cbc0045I mipstart provided solution with cost 127.464<br>
[..]</small><br>
<br>
</i><small>What does mean the warning?<br>
Is there something i miss.<br>
<br>
Thanks<br>
<br>
Yves<br>
</small></big><br>
</font><br>
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Haroldo Gambini Santos
D.Sc, Computer Science
Universidade Federal de Ouro Preto
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.decom.ufop.br/haroldo/">http://www.decom.ufop.br/haroldo/</a></pre>
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<pre class="moz-signature" cols="72">--
==================================================
Haroldo Gambini Santos
D.Sc, Computer Science
Universidade Federal de Ouro Preto
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.decom.ufop.br/haroldo/">http://www.decom.ufop.br/haroldo/</a></pre>
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