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<div class="moz-cite-prefix">Marcel,<br>
<br>
Send me the model.<br>
<br>
John Forrest<br>
<br>
On 18/04/13 11:53, Marcel Hunting wrote:<br>
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<p class="MsoNormal"><span>Hi,</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>I have a small MIP problem for which
CBC 2.7.5 returns infeasible while the problem is in fact
feasible. This is part of the log file:</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>Optimal - objective value 5625.1701</span></p>
<p class="MsoNormal"><span>Integer solution of -5625.1701 found
by feasibility pump after 0 iterations and 0 nodes (0.17
seconds)</span></p>
<p class="MsoNormal"><span>Objective coefficients multiple of
0.1</span></p>
<p class="MsoNormal"><span>Search completed - best objective
-5625.170085470087, took 0 iterations and 0 nodes (0.18
seconds)</span></p>
<p class="MsoNormal"><span>Maximum depth 0, 0 variables fixed on
reduced cost</span></p>
<p class="MsoNormal"><span>0 Obj 5625.1701 Primal inf 2.2580657
(48)</span></p>
<p class="MsoNormal"><span>3 Obj 5623.2228 Primal inf 5.4953389
(94)</span></p>
<p class="MsoNormal"><span>…</span></p>
<p class="MsoNormal"><span>40 Obj 5612.1607 Primal inf
1.3658683 (28)</span></p>
<p class="MsoNormal"><span>Primal infeasible - objective value
5612.1607</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>The objective value (5625.1701) of
the integer solution found by the feasibility pump algorithm
corresponds to the objective value of the optimal solution.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>It seems that CBC does some kind of
postsolve which fixes variables and that appears to be
infeasible. Does CBC have a parameter to switch off the
postsolve?</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>I can provide a LP or MPS file of the
model. The scaling of the model seems ok.</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>Best regards,</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>Marcel Hunting</span></p>
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