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<div class="moz-cite-prefix">Mike,<br>
<br>
Fix is in svn 2.9 - won't be in a release just yet.<br>
<br>
John Forrest<br>
On 10/02/15 13:41, Mike Steglich wrote:<br>
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cite="mid:5FE2C1EE-762C-4178-BC04-63EACF4D74D8@stegger.net"
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Hi John,
<div class=""><br class="">
</div>
<div class="">I tested Cbc 2.9.2 on OS X with the attached free
mps file and found the same issue for this maximisation problem:</div>
<div class=""><br class="">
</div>
<div class=""><i class="">Coin0505I Presolved problem not optimal,
resolve after postsolve<br class="">
Cgl0013I Postprocessed model is infeasible - possible
tolerance issue - try without preprocessing<br class="">
7 relaxed row infeasibilities - summing to 1604<br class="">
7 relaxed row infeasibilities - summing to 1604<br class="">
7 relaxed row infeasibilities - summing to 1604<br class="">
<br class="">
Result - Optimal solution found<br class="">
<br class="">
Objective value: 56640.00000000<br class="">
Enumerated nodes: 0</i><br class="">
<br class="">
</div>
<div class="">It is shown that an optimal solution was found ...
but as for the example I sent Yesterday .... one of the
non-negative variables (x[1,1]) is shown in the solution file
with a negative value. </div>
<div class="">Without preprocessing the problem is stated as
infeasible.</div>
<div class=""><br class="">
</div>
<div class="">Thanks,</div>
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<div class="">Mike</div>
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<div class="">Am 10.02.2015 um 11:33 schrieb John Forrest
<<a moz-do-not-send="true"
href="mailto:john.forrest@fastercoin.com" class="">john.forrest@fastercoin.com</a>>:</div>
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<div class="moz-cite-prefix">Mike,<br class="">
<br class="">
The problem is due to the elements of 1.0e9 in model.
In postprocessing this led to values of 1.0e-9 which
is just on a particular tolerance.<br class="">
<br class="">
Without preprocessing my tests gave correct solution.<br
class="">
<br class="">
It was a bug - I have made postprocessing more robust
in 2.9.<br class="">
<br class="">
John Forrest<br class="">
<br class="">
On 09/02/15 11:39, Mike Steglich wrote:<br class="">
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cite="mid:D88F7C67-CB49-42BD-8DDB-02BB46408EF5@berlin.de"
type="cite" class="">
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Hello,
<div class=""><br class="">
</div>
<div class="">I've got an interesting behaviour with
the attached mps file. When I run this problem with
the CBC binary (2.8.9 on OS X and 2.9.0 on Win8.1)
then I got the following information:</div>
<div class=""><br class="">
</div>
<div class="">...</div>
<div class=""><i class="">Coin0505I Presolved problem
not optimal, resolve after postsolve<br class="">
Cgl0013I Postprocessed model is infeasible -
possible tolerance issue - try without
preprocessing<br class="">
16 relaxed row infeasibilities - summing to 193<br
class="">
16 relaxed row infeasibilities - summing to 193<br
class="">
16 relaxed row infeasibilities - summing to 193<br
class="">
<br class="">
Result - Optimal solution found<br class="">
<br class="">
Objective value: 813.00000000</i></div>
<div class="">...</div>
<div class=""><br class="">
</div>
<div class="">The solution file (It doesn't matter
whether I use the solu or gsolu option) shows an
different objective function value of 1925 and
values for the variables that are obviously
infeasible. When I set the preprocessing off then
the problem is stated as infeasible.</div>
<div class=""><br class="">
</div>
<div class="">It could be possible that the problem
formulation and therefore the mps file is stupid.
But when I use the same mps file with glpk, scip and
Cplex then I'm able to find in any case an optimal
solution with the objective function value 813 (that
is also shown by Cbc).</div>
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<div class="">Thanks,</div>
<div class=""><br class="">
</div>
<div class="">Mike</div>
<br class="">
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