<div>Thanks Andreas and Mikhail.</div>
<div> </div>
<div>We presolve with CPLEX, which reduces the time a little bit.</div>
<div> </div>
<div>Best regards</div>
<div> </div>
<div>Vatsal<br><br></div>
<div class="gmail_quote">On Thu, Oct 23, 2008 at 2:47 PM, Mikhail Nediak <span dir="ltr"><<a href="mailto:MNediak@business.queensu.ca">MNediak@business.queensu.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><br><font face="sans-serif" size="2">Well, hypothetically, could not one try to find a feasible solution to</font> <br>
<div class="Ih2E3d"><font face="sans-serif" size="2">min 0^T x</font> <br><font face="sans-serif" size="2"> A x = b</font> <br><br></div><font face="sans-serif" size="2">using CPLEX? Of course, CPLEX was NOT specifically designed to do this...</font> <br>
<br><font face="sans-serif" size="2">However, I wonder if linear algebra routines in CPLEX would beat MUMPS when accessed like that.</font> <br><br><font face="sans-serif" size="2">Mikhail<br></font><br><br><br>
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<td><font face="sans-serif" color="#5f5f5f" size="1">From:</font>
<td><font face="sans-serif" size="1">Andreas Waechter <<a href="mailto:andreasw@watson.ibm.com" target="_blank">andreasw@watson.ibm.com</a>></font>
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<td><font face="sans-serif" color="#5f5f5f" size="1">To:</font>
<td><font face="sans-serif" size="1">Vatsal Bhatt <<a href="mailto:vatsalbhatt@gmail.com" target="_blank">vatsalbhatt@gmail.com</a>></font>
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<td valign="top"><font face="sans-serif" color="#5f5f5f" size="1">Cc:</font>
<td><font face="sans-serif" size="1"><a href="mailto:ipopt@list.coin-or.org" target="_blank">ipopt@list.coin-or.org</a></font>
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<td><font face="sans-serif" color="#5f5f5f" size="1">Date:</font>
<td><font face="sans-serif" size="1">23/10/2008 02:38 PM</font>
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<td><font face="sans-serif" color="#5f5f5f" size="1">Subject:</font>
<td><font face="sans-serif" size="1">Re: [Ipopt] IPOPT with CPLEX?</font></td></td></tr></td></td></tr></td></td></tr></td></td></tr></td></td></tr></tbody></table><br>
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<div class="Wj3C7c">Hi Vatsal,<br><br>MUMPS and Pardiso are solving linear systems, i.e., for a given matrix A <br>and a vector b, it gets a vector x that satisfies<br><br>Ax = b<br><br>Here, A is a symmetric indefinite matrix.<br>
<br>CLPEX is a Linear Programming solver. This is something entirely <br>different. It solves LPs like<br><br>min c^T x<br> A x >= b<br><br>CLPEX has completely different functionality from MUMPS and cannot replace <br>
it.<br><br>Andreas<br><br>On Thu, 23 Oct 2008, Vatsal Bhatt wrote:<br><br>> Many thanks to the developers of IPOPT for large scale NLPs and making it<br>> opensource.<br>><br>> Since our MARKAL-MACRO energy systems analysis model had a problem running<br>
> with other solvers, GAMS suggested us to use IPOPT. It handles our model<br>> well, we are happy that atleast it runs...<br>><br>> Since our model has several thousand equations with several hundred thousand<br>
> non-zeros, it takes nearly an hour for a run. It uses MUMPS as a linear<br>> solver and the documentation has suggestions on using PARDISO.<br>><br>> We use CPLEX for our LP based MARKAL, which solves the same system in LP<br>
> within 5 minutes (without 5 macro economic equations).<br>><br>> Would it be possible for us to use CPLEX instead of MUMPS within IPOPT?<br>><br>> Thanks in advance for your help.<br>><br>> Vatsal<br>
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