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<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Pratim,<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>AMPL includes the initial values of the variables in the file that
it writes for the solver, but it is up to each solver interface to decide what
to do with these values. Most likely the current version of the CBC AMPL
interface is not making use of the initial values. CBC's AMPL interface
is not part of the AMPL program; it was written (and may be enhanced)
independently of AMPL. The source code for the interface can be found
with the rest of the CBC source.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Note that even if you supply an initial incumbent solution to a
branch-and-bound code such as CBC, it will have to build a search tree from the
root. The initial solution may enable the tree to be pruned more quickly,
though.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Bob Fourer<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><a href="mailto:4er@ampl.com">4er@ampl.com</a><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-right:172.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> Pratim Vakish
[mailto:pratim_usc@hotmail.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, October 03, 2008
9:04 AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">4er@iems.northwestern.edu</st1:PersonName>;
cbc@list.coin-or.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> RE: [Cbc] Initial integer
feasible solution</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'>Thanks Bob.<br>
<br>
However, I think that I am doing what you suggest and it is not working.<br>
Here is what I do.<br>
I set my integer variables to a given value as follows:<br>
<br>
let {i in T} x[i]:= xinit[i];<br>
<br>
The solution defined by the xinit values is integer feasible.<br>
However, CBC does not use this integer solution as the incumbent one in the
tree, since CBC takes a lot of time and nodes in the tree before coming up with
a first integer feasible solution.<br>
<br>
So could you tell me why I am having this issue and how to resolve it?<br>
<br>
<br>
Many thanks,<br>
<br>
Pratim<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><br>
<br>
<o:p></o:p></span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>From: <st1:PersonName w:st="on">4er@iems.northwestern.edu</st1:PersonName><br>
To: pratim_usc@hotmail.com; cbc@list.coin-or.org<br>
Subject: RE: [Cbc] Initial integer feasible solution<br>
Date: Thu, 2 Oct 2008 23:51:09 -0500<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal style='margin-right:208.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Just assign the incumbent values to the AMPL variables, and AMPL
will automatically pass those values to the solver. Then the solver is
free to do whatever it can with them.</span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:208.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'> </span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:208.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Bob Fourer</span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:208.5pt'><st1:PersonName w:st="on"><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New";color:black'>4er@ampl.com</span></font></st1:PersonName><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:208.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'> </span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-right:208.5pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'> </span></font><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
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border-color:-moz-use-text-color -moz-use-text-color -moz-use-text-color blue'>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
cbc-bounces@list.coin-or.org [mailto:cbc-bounces@list.coin-or.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Pratim Vakish<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, October 02, 2008
8:12 PM<br>
<b><span style='font-weight:bold'>To:</span></b> cbc@list.coin-or.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Cbc] Initial integer
feasible solution<o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font><font size=2 face=Tahoma><span style='font-size:
10.0pt;font-family:Tahoma'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'>Hello,<br>
<br>
I am solving large-scale MIP problems using the CBC solver and the AMPL
interface.<br>
<br>
For some problems, I know an integer feasible solution of good
"quality" and I would like CBC to use it as first incumbent solution
in the branch-and-bound tree.<br>
I think that the CBC option</span></font><font size=2 face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New"'> </span></font><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>CbcModel::setBestSolution()
allows to do that.<br>
<br>
I use AMPL and I would like to know what is the AMPL command to use this
option?<br>
How can I tell CBC (with AMPL) which solution I would like to use as first
incumbent solution?<br>
<br>
Thanks very much,<br>
<br>
Pratim<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'> <o:p></o:p></span></font></p>
</div>
</div>
<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'><o:p> </o:p></span></font></p>
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face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
<hr size=2 width="100%" align=center>
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<p class=MsoNormal><font size=2 face=Tahoma><span style='font-size:10.0pt;
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