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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’m not 100% sure, but I think the “MaximumSolutions”
is meant to do something else. It’s a limit on the search tree, like MaximumNodes.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>What you can do to get multiple solutions is add constraints
that cut off all previous solutions. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The particular kind of constraint that you need to add to cut off
a solution depends on your problem. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Let’s use what you describe. Say in the first solve you
find the solution x0, with S = {i | x0_i = 1}. Then you could add a constraint
(again, depending on your problem) <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Sum_{i in S} x_i <= |S| - 1<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>And solve this new problem from scratch. You can continue this,
adding another constraint each time, as long as you want. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>For example, you can continue this until the objective value is
too far from the original obj val, or something.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Regards,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Jan-Willem<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> osi-bounces@list.coin-or.org
[mailto:osi-bounces@list.coin-or.org] <b>On Behalf Of </b>Nathann Cohen<br>
<b>Sent:</b> 31 July 2009 11:02<br>
<b>To:</b> osi@list.coin-or.org<br>
<b>Subject:</b> [Osi] Several integers solutions<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<div>
<p class=MsoNormal>Hello everybody !<br>
<br>
I have been solving continuous and integer programs with Cbc for some time now
and it works absolutely fine ! <br>
Now, I would like to add some spices to what I am doing with it, by trying to
compute several integers solutions to linear programs.<br>
<br>
For example, I would like the following program ( with x and y binary variables
) :<br>
<br>
Max:<br>
x + y<br>
Constraints :<br>
x + y <= 1<br>
<br>
to return the two solutions : x = 0, y=1 and x=1,y=0.<br>
<br>
I saw there were functions in OsiClpInterface like setMaximumSolution and
getMaximumSolutions. I also found the function getSolutionCount in CbcModel but
it does not seem to do what I want it to do ;-)<br>
I set the Maximum Number of Solutions to 200 and checked with
getMaximumSolutions there was no problem assigning the value, but when I solve
the previous problem getSolutionCount always return 1. Would you know how to
make it work properly ? Would you have an example where several solutions
are found, which I could read to see both how it is done, and how to iterate
through all the solutions found after ? It it possible to set the infinity as
the MaximumNumber of solution if I want all of them ( I know this can grow
quite huge ! )<br>
<br>
Thank you very much for your help !<br>
<span style='color:#888888'><br>
Nathann Cohen</span><o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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