Though you may be right, you can't make conclusion like that.<br><br>a) I think AMPL has it's own presolver running before passing the problem to the solver.<br><br>b) Comparing from command prompt and the problem passed by AMPL to CLP could give you a different permutation order of constraints and variable.<br>
<br>In both situations you can (and often will) have different solution paths.<br><br><div class="gmail_quote">On Fri, Jul 27, 2012 at 7:41 PM, Ahmadi, Javad <span dir="ltr"><<a href="mailto:javad.ahmadi@amd.com" target="_blank">javad.ahmadi@amd.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div link="blue" vlink="purple" lang="EN-US">
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">NAME BLANK
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">ROWS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> N OBJROW<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> G R0000000<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> L R0000001<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> E R0000002<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">COLUMNS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> C0000000 OBJROW 1. R0000000 1.
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> C0000000 R0000001 1. R0000002 1.
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">RHS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> RHS R0000000 1. R0000001 2.
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> RHS R0000002 1.1
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">ENDATA<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">At line 1 NAME BLANK<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">At line 2 ROWS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">At line 7 COLUMNS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">At line 10 RHS<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">At line 13 ENDATA<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Problem BLANK has 3 rows, 1 columns and 3 elements<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Model was imported from .\junk.mps in 0.01 seconds<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Clp:solve<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Presolve 0 (-3) rows, 0 (-1) columns and 0 (-3) elements<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Empty problem - 0 rows, 0 columns and 0 elements<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Optimal - objective value 1.1<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">After Postsolve, objective 1.1, infeasibilities - dual 0 (0), primal 0 (0)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Optimal objective 1.1 - 0 iterations time 0.012, Presolve 0.01<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Nothing to do with CLP!<u></u><u></u></span></p>
<div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:clp-bounces@list.coin-or.org" target="_blank">clp-bounces@list.coin-or.org</a> [mailto:<a href="mailto:clp-bounces@list.coin-or.org" target="_blank">clp-bounces@list.coin-or.org</a>]
<b>On Behalf Of </b>Ted Ralphs<br>
<b>Sent:</b> Friday, July 27, 2012 12:09 PM<br>
<b>To:</b> <a href="mailto:clp@list.coin-or.org" target="_blank">clp@list.coin-or.org</a><br>
<b>Subject:</b> [Clp] Fwd: [Symphony] Incorrect solution for a simple linear programming model<u></u><u></u></span></p>
</div><div><div class="h5">
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi all,<br>
<br>
There have been a number of reports of Clp failing to solve very simple LPs. The below was posted to the SYMPHONY mailing list, but since the problem in question is an LP and is not pre-processed by SYMPHONY, this seems to be a problem with Clp. I am looking
into it, but I thought I would throw it onto the Clp list in case anyone else is seeing the same thing or wants to help.<br>
<br>
Cheers,<br>
<br>
Ted<u></u><u></u></p>
<div>
<p class="MsoNormal">---------- Forwarded message ----------<br>
From: <b>Federico Larumbe</b> <<a href="mailto:federico.larumbe@polymtl.ca" target="_blank">federico.larumbe@polymtl.ca</a>><br>
Date: Thu, Jul 19, 2012 at 4:46 PM<br>
Subject: [Symphony] Incorrect solution for a simple linear programming model<br>
To: <a href="mailto:symphony@list.coin-or.org" target="_blank">symphony@list.coin-or.org</a><br>
<br>
<br>
Hi, <u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">I am testing Symphony with a simple example in AMPL format:<u></u><u></u></p>
</div>
<div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">symphony -F file.mod -D file.dat<u></u><u></u></span></p>
</div>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<blockquote style="margin-left:30.0pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">-- file.mod ------------------</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">var y >= 0;</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">minimize ObjectiveFunction: y;</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">subject to C1: y >= 1.0;</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">subject to C2: y <= 2.0;</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">subject to C3: y = 1.1;</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">end;</span><u></u><u></u></p>
</div>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">------------------------------</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">-- file.dat ------------------</span><u></u><u></u></p>
</div>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">data;</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">end;</span><u></u><u></u></p>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">------------------------------</span><u></u><u></u></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">The solution given by the program is 2.0 instead of 1.1 (see attached file). If I choose maximize, the solution is 1.0. If I remove C3, the problem is unbounded. Is there any option that I
missing?</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">I compiled Sympthony in SUSE Linux with gcc 4.5.1 with the following commands:</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<blockquote style="margin-left:30.0pt;margin-right:0in">
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">./configure --with-gmpl --enable-openm</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Courier New"">make</span><u></u><u></u></p>
</div>
</blockquote>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Thanks a lot,</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Federico.</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="color:#888888"><u></u> <u></u></span></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span><span style="color:#888888">--
</span></span><span style="color:#888888"><br>
<span>Federico Larumbe</span><br>
<span>École Polytechnique de Montréal</span><br>
<span>Montréal H3C 3A9</span><br>
<br>
<span>Group for Research in Decision Analysis (GERAD)</span><br>
<span>tel <a href="tel:%2B1%20514%203406053%20xt%206931" target="_blank">
+1 514 3406053 xt 6931</a></span><br>
<span>fax <a href="tel:%2B1%20514%203405665" target="_blank">+1 514 3405665</a></span><br>
<span><a href="http://www.gerad.ca/en/directory/details.php?id=1214" target="_blank">http://www.gerad.ca/en/directory/details.php?id=1214</a></span><br>
</span><br>
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</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br clear="all">
<br>
-- <br>
Dr. Ted Ralphs<br>
Associate Professor, Lehigh University<br>
<a href="tel:%28610%29%20628-1280" value="+16106281280" target="_blank">(610) 628-1280</a><br>
ted 'at' lehigh 'dot' edu<br>
<a href="http://coral.ie.lehigh.edu/%7Eted" target="_blank">coral.ie.lehigh.edu/~ted</a><u></u><u></u></p>
</div></div></div>
</div>
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<br></blockquote></div><br>