<br><font size=2 face="sans-serif">Paulo,</font>
<br>
<br><font size=2 face="sans-serif">A valid basis may need artificial variables.
For instance if two rows of the matrix are identical an artificial
must be in basis.</font>
<br>
<br><font size=2 face="sans-serif">John Forrest</font>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>"Paulo J. S. Silva"
<pjssilva@ime.usp.br></b> </font>
<br><font size=1 face="sans-serif">Sent by: coin-lpsolver-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">03/08/2005 01:13 PM</font>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td valign=top><font size=1 face="sans-serif">coin-lpsolver@list.coin-or.org</font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">Aritifical variables, was:
Re: [Coin-lpsolver] Parametric Analysis using
CLP + OSI</font></table>
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<br><font size=2><tt><br>
> Paulo, <br>
> <br>
> It depends how you are picking up basis information. With a
problem<br>
> of n columns and m rows Clp numbers the structural variables
(column)<br>
> 0 through n-1 and the artificial/slack variables n through n+m-1.
<br>
> <br>
> John Forrest <br>
<br>
<br>
In that case what I do is:<br>
<br>
s.initialSolve()<br>
s.enableSimplexInterface(True)<br>
s.getBasics(basics)<br>
<br>
If I look at basics I get a 469 in the basis. My problem has 460<br>
variables and 198 rows. Hence, using your explanation, it looks like<br>
there are still artificial variables in the basis. <br>
<br>
Is there a way to pick up a "valid" basis, using only structural<br>
variables? <br>
<br>
Paulo<br>
-- <br>
Paulo José da Silva e Silva <br>
Professor Assistente do Dep. de Ciência da Computação<br>
(Assistant Professor of the Computer Science Dept.)<br>
Universidade de São Paulo - Brazil<br>
<br>
e-mail: pjssilva@ime.usp.br Web: http://www.ime.usp.br/~pjssilva<br>
<br>
Teoria é o que não entendemos o (Theory is something we don't)<br>
suficiente para chamar de prática. (understand well enough to call) <br>
(practice)<br>
<br>
<br>
<br>
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</tt></font>
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