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<span style="font-size: 12pt;">Dear Geri, </span><br>
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I hope you have gotten your answer by now, but if you haven't, I would like to give you some more tips. </p>
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<li>Yes there are few ways to update the coefficient of variables in scip. </li></ol>
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<li><span style="font-size: 12pt;"> One is to add a number to the coefficient, "SCIP_CALL(SCIPaddVarObj(scip,var,value))"</span></li><li><span style="font-size: 12pt;"> Another is to replace the coefficient, "SCIP_CALL(SCIPchgVarObj(scip,var,new_weight))"</span></li></ul>
2. But I would like you to also be aware that SCIP has different stages and transferring problems and freeing those transforms is a big deal. Otherwise, even if you are able to change the weight once, you won't be able to do it again. </div>
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<div id="divtagdefaultwrapper" style="" dir="ltr">Though it will depend on your code, here is one example. Let's say you're in a loop. The following step worked for me:</div>
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<div id="divtagdefaultwrapper" style="" dir="ltr">for i=1,2,...</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> add a value to your coefficient</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> transform the problem</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> solve it</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> free the transform </div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> transform the problem again before the start of the new loop</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> change the variable to the original if you want to</div>
<div id="divtagdefaultwrapper" style="" dir="ltr"> free the transform</div>
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<div id="divtagdefaultwrapper" style="" dir="ltr">These is a bit complicated, but it just shows you that you can experiment on your code and that there is a way. </div>
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<div id="divtagdefaultwrapper" style="" dir="ltr">Hope it was helpful, </div>
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<div id="divtagdefaultwrapper" style="" dir="ltr">Best regards, </div>
<div id="divtagdefaultwrapper" style="" dir="ltr">Dawit</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>Von:</b> Scip <scip-bounces@zib.de> im Auftrag von Geri K <gkovacsds@gmail.com><br>
<b>Gesendet:</b> Mittwoch, 27. Oktober 2021 15:23<br>
<b>An:</b> scip@zib.de<br>
<b>Betreff:</b> [SCIP] Re-solving problems with constraint change?</font>
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<div class="PlainText">Dear All,<br>
is it possible with the SCIP C API to call solving again with changed<br>
constraint linear coefficients?<br>
So it would be probably faster than re-creating the whole problem.<br>
I would not change the constraint variables included, only their<br>
coefficients.<br>
I could not find an example or api documentation for this, is it possible<br>
and if yes, what calls are needed?<br>
Thank you,<br>
Geri<br>
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