<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.E-MailFormatvorlage17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 2.0cm 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="DE" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-GB">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am currently working on a specific MIP, where it is easy to calculate a feasible solution in advance. Hence, I am looking for an algorithm to improve an initial solution, for example via local search.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I know, there is the “CbcHeuristicLocal” class and I even found some examples. When I tried to implement the algorithm in the following way
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:teal">OsiClpSolverInterface</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black"> clp;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:teal">CbcModel</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black"> model(clp);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">//[…set initial solution…]</span><span lang="EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:teal">CbcHeuristicLocal</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black"> heuristicLocal(model);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">heuristicLocal.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">setSearchType</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">(1);
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">heuristicLocal.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">setFractionSmall</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">(0.5);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">heuristicLocal.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">setHeuristicName</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">(</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">"local"</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">model.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">addHeuristic</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">(&heuristicLocal);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">//[…]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">model.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">initialSolve</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">model.</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:maroon">branchAndBound</span><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black">();<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:9.5pt;font-family:Consolas;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">the solution didn’t improve, and I got the following log massage “Cbc0045I Heuristic local took 0 seconds (no good)”. So, I think the algorithm didn’t even start.</span><span lang="EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am wondering if I missed to set some parameters or if I can’t use this class as I thought?
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Has somebody some experiences with local search, the CbcHeuristicLocal class or with the CbcTreeLocal class? It would be great to get more information on this topic!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thank you in advance,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Irina<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>