<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>I don't know the model and the problem it is related to, so I have no idea what to change.</div>
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<div>Mine is just a consideration on the divergence you observe between the model and the solution: if the solution is feasible and optimal for the model but it is not satisfactory for you, then it is the model that does not correspond to your set of solutions and objective function and should be revised.</div>
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<div>Hope this helps. Regards,</div>
<div>Pietro</div>
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<div style="margin:0 0 10px 0;"><b>Sent:</b> Wednesday, May 20, 2020 at 11:56 AM<br/>
<b>From:</b> "Divyayan Dey" <divyayanrishi@gmail.com><br/>
<b>To:</b> "Pietro Belotti" <pbelotti@gmx.com><br/>
<b>Subject:</b> Re: [Couenne] Regarding optimization issues with couenne</div>
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<div>Do you mean to change the model from Concrete to Abstract? But my model has static parameters ,so I don't think it needs to be made Abstract. What are some modelling changes you think need to be made?
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<div><font face="georgia, serif"><b>Divyayan Dey</b>,</font>
<div><font face="georgia, serif">3rd Year Undergraduate,</font></div>
<div><font face="georgia, serif">Institute of Radiophysics and Electronics,</font></div>
<div><font face="georgia, serif">University of Calcutta</font></div>
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<div class="gmail_attr">On Wed, May 20, 2020 at 2:49 AM Pietro Belotti <<a href="mailto:pbelotti@gmx.com" onclick="parent.window.location.href='mailto:pbelotti@gmx.com'; return false;" target="_blank">pbelotti@gmx.com</a>> wrote:</div>
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<div>Hi Divyayan,</div>
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<div>the initial solution is only useful to Couenne as a cutoff, i.e. a value such that the portion of solution space with objective above it is excluded from the search.</div>
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<div>If the optimal solution you get is unsatisfactory, it might be a matter of modeling. If the solution you found satisfies all constraints and minimizes the objective, the only way to receive a more "balanced", as I assume you're looking for, solution is to change the model itself.</div>
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<div>Hope this helps. Regards,</div>
<div>Pietro
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<div style="margin: 0.0px 0.0px 10.0px;"><b>Sent:</b> Monday, May 18, 2020 at 4:03 AM<br/>
<b>From:</b> "Divyayan Dey" <<a href="mailto:divyayanrishi@gmail.com" onclick="parent.window.location.href='mailto:divyayanrishi@gmail.com'; return false;" target="_blank">divyayanrishi@gmail.com</a>><br/>
<b>To:</b> <a href="mailto:couenne@list.coin-or.org" onclick="parent.window.location.href='mailto:couenne@list.coin-or.org'; return false;" target="_blank">couenne@list.coin-or.org</a><br/>
<b>Subject:</b> [Couenne] Regarding optimization issues with couenne</div>
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<div><span style="font-family: sans-serif;font-size: 12.8px;">Sir,</span>
<div style="font-family: sans-serif;font-size: 12.8px;">I am Divyayan Dey, an Electronics and Communication Engineering student from India. </div>
<div style="font-family: sans-serif;font-size: 12.8px;">I am solving an optimization problem using couenne solver in Pyomo(the problem being non-convex). I have a finite capacity to distribute among a set of elements. However, with any initial guess <img alt="x0" height="11" src="https://s0.wp.com/latex.php?zoom=3&bg=ffffff&fg=000000&s=0&latex=x0" style="display: inline;vertical-align: -0.333px;" width="16"/> provided to the solver, the optimized vector is messed up badly; e.g., with a capacity of 1000 to distribute ,the optimized vector <img alt="x" height="7" src="https://s0.wp.com/latex.php?zoom=3&bg=ffffff&fg=000000&s=0&latex=x" style="display: inline;" width="8"/> gives [897,1,1,1,1....] . With a capacity of 500, the vector <img alt="x" height="7" src="https://s0.wp.com/latex.php?zoom=3&bg=ffffff&fg=000000&s=0&latex=x" style="display: inline;" width="8"/> is [397,1,1,...]. And when the optimization is done only in the convex portion of the objective function, the initial guess <img alt="x0" height="11" src="https://s0.wp.com/latex.php?zoom=3&bg=ffffff&fg=000000&s=0&latex=x0" style="display: inline;vertical-align: -0.333px;" width="16"/> is returned itself showing no evaluations done. What could be a possible reason for this? I can add the code if you would like to introspect. </div>
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<div style="font-family: sans-serif;font-size: 12.8px;">Thanks. Regards,</div>
<div style="font-family: sans-serif;font-size: 12.8px;">Divyayan Dey </div>
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