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<body class='hmmessage'><div dir='ltr'>Dear Gregor,<div><br></div><div>Yes, i confirm very nice as an exercice ;)</div><div>It's much clear, now</div><div><br></div><div>Thank's and regards </div><div><br></div><div>---</div><div><span style="font-size: 12pt;">Abdelkader Ouali </span></div><div><br><div><hr id="stopSpelling">Date: Wed, 9 Jul 2014 17:19:06 +0200<br>From: hendel@zib.de<br>To: scip@zib.de<br>Subject: Re: [Scip] help : How to write dual problem<br><br>
<div class="ecxmoz-cite-prefix">Dear Abdelkader Ouali,<br>
<br>
I am afraid there is no ad-hoc method available for this in SCIP.
The methods available through the <a href="http://scip.zib.de/doc/html_devel/cons__linear_8h.php" target="_blank">linear
constraint<br>
handler</a> might be sufficient here:<br>
<br>
1. Create a secondary SCIP-instance dualscip and a problem inside
dualscip.<br>
2. Create variables for every linear constraint in dualscip<br>
3. Create a new linear constraint in dualscip for every variable<br>
4. Iterate over the constraints once in order to have their
variables, vals (=coefficients), and number, and add<br>
the coefficients for the corresponding dual variable of this
constraint to every dual constraint it should appear in.<br>
5. Now you can use the LP-writer for the dualscip-Problem.<br>
<br>
This is quite a nice SCIP-exercise, isn't it? :)<br>
<br>
The reason why SCIP does not come with such a functionality (yet)
is its constraint-based nature. It does not<br>
always make sense to speak of the dual of a SCIP problem. The dual
of the LP that SCIP builds internally might<br>
be different from what you exspect, because the problem has
already undergone a transformation through<br>
various presolving steps.<br>
<br>
Kind regards<br>
Gregor<br>
<br>
<br>
Am 09.07.2014 10:01, schrieb Abdelkader Ouali:<br>
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<div dir="ltr">Hello,
<div><br>
</div>
<div>How to write dual problem of the original problem in lp
format file </div>
<div>using SCIP routines</div>
<div><br>
</div>
<div>Thanks </div>
<div><br>
</div>
<div>---</div>
<div>Abdelkader Ouali</div>
<div><br>
</div>
</div>
<br>
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