Hi Nicolas,<br>No, I don't have MINOS and I have no idea what the problem is.<br>There is another MINLP solver in COIN-OR which is more aimed at global optimization. Its name is LaGO. You can find it there:<br><a href="https://projects.coin-or.org/LaGO">
https://projects.coin-or.org/LaGO</a><br><br>Best regards,<br>Pierre<br><br><div><span class="gmail_quote">On 9/11/07, <b class="gmail_sendername">Nicolas BERGER</b> <<a href="mailto:Nicolas.Berger@univ-nantes.fr">Nicolas.Berger@univ-nantes.fr
</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Thank you Pierre !! Now it works indeed... when Ampl uses Bonmin. No idea
<br>about the problem with MINOS ?<br><br>And, by the way, do you know other free MINLP solvers ?<br><br><br>Nicolas<br><br><br>> Hi Nicolas,<br>><br>> The problem is that Ipopt was not able to solve the root node relaxation.
<br>> Apparently some of the options changed by bonmin are the cause for this<br>> (although I don't really understand why).<br>> You can try with the option file that I attach (put the file in the<br>> directory where you run ampl). With it I get a solution of same objective
<br>> value as Baron.<br>> Best regards,<br>> Pierre<br>> On 9/10/07, Nicolas BERGER <<a href="mailto:Nicolas.Berger@univ-nantes.fr">Nicolas.Berger@univ-nantes.fr</a>> wrote:<br>>><br>>> Hi<br>
>><br>>><br>>> I am trying to solve this problem :<br>>><br>>> ------------------------------------------------------------------<br>>> var x0 integer >= 1 <= 10 ;<br>>> var y0 integer >= 1 <= 10 ;
<br>>> var x1 >= 1 <= 10 ;<br>>> var y1 >= 1 <= 10 ;<br>>> var x2 >= 1 <= 10 ;<br>>> var y2 >= 1 <= 10 ;<br>>><br>>> maximize dist: (x0-x1)**2 + (y0-y1)**2 + (x0-x2)**2 +
<br>>> (y0-y2)**2 + (x1-x2)**2 + (y1-y2)**2 ;<br>>><br>>><br>>> subject to<br>>> e01: (x0-x1)**2 + (y0-y1)**2 >= 12.5 ;<br>>> e10: (x0-x1)**2 + (y0-y1)**2 <= 64 ;
<br>>> e02: (x0-x2)**2 + (y0-y2)**2 >= 12.5 ;<br>>> e20: (x0-x2)**2 + (y0-y2)**2 <= 64 ;<br>>> e12: (x1-x2)**2 + (y1-y2)**2 >= 12.5 ;<br>>> e21: (x1-x2)**2 + (y1-y2)**2 <= 64 ;<br>>>
<br>>> solve ;<br>>> display x0,y0,x1, y1 ,x2, y2 ;<br>>> ------------------------------------------------------------------------<br>>><br>>><br>>><br>>> Here is the solution to this small problem (given by gams/baron) :
<br>>><br>>><br>>> -----------------------------------------------------------------------------------<br>>> LOWER LEVEL UPPER<br>>> MARGINAL<br>
>><br>>> ---- VAR objvar -INF 192.0000 +INF<br>>> .<br>>> ---- VAR x0 1.0000 1.0000 10.0000<br>>> EPS<br>>> ---- VAR y0
1.0000 6.0000 10.0000<br>>> EPS<br>>> ---- VAR x1 1.0000 7.9282 10.0000<br>>> .<br>>> ---- VAR y1 1.0000 10.0000
10.0000<br>>> .<br>>> ---- VAR x2 1.0000 7.9282 10.0000<br>>> .<br>>> ---- VAR y2 1.0000 2.0000 10.0000<br>>> .
<br>>><br>>> -----------------------------------------------------------------------------------<br>>><br>>><br>>><br>>> Now here is what ampl returns when I call it on this problem :<br>
>><br>>> --------------------------------------------------------<br>>> MINOS 5.5: ignoring integrality of 2 variables<br>>> MINOS 5.5: infeasible problem (or bad starting guess).<br>>> 0 iterations
<br>>> Nonlin evals: obj = 7, grad = 6, constrs = 7, Jac = 6.<br>>> x0 = 1<br>>> y0 = 1<br>>> x1 = 1<br>>> y1 = 1<br>>> x2 = 1<br>>> y2 = 1<br>>> --------------------------------------------------------
<br>>><br>>><br>>><br>>> And this is what I get when I add "option solver bonmin" in the problem<br>>> file :<br>>><br>>><br>>> -------------------------------------------------------------------------------------
<br>>> bonmin:<br>>><br>>><br>>> ******************************************************************************<br>>> This program contains Ipopt, a library for large-scale nonlinear<br>>> optimization.
<br>>> Ipopt is released as open source code under the Common Public License<br>>> (CPL).<br>>> For more information visit <a href="http://projects.coin-or.org/Ipopt">http://projects.coin-or.org/Ipopt
</a><br>>><br>>> ******************************************************************************<br>>><br>>> IpOp0008I<br>>> Num Status Obj It time<br>
>> IpOp0009I 1 FAILED -0 3000 2.81218<br>>> IpOp0010I r1 FAILED -0 3000 2.78817<br>>> Ipopt exited with error code -1 Maximum Iterations Exceeded
<br>>> can't open /tmp/at23241.sol<br>>><br>>> -------------------------------------------------------------------------------------<br>>><br>>> What am I doing wrong ? Where to start debugging ? :)
<br>>><br>>><br>>><br>>><br>>> >From Nantes, France,<br>>> BERGER Nicolas<br>>><br>>><br>>><br>>> _______________________________________________<br>>> Bonmin mailing list
<br>>> <a href="mailto:Bonmin@list.coin-or.org">Bonmin@list.coin-or.org</a><br>>> <a href="http://list.coin-or.org/mailman/listinfo/bonmin">http://list.coin-or.org/mailman/listinfo/bonmin</a><br>>><br>>
<br><br><br></blockquote></div><br>