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<p class=MsoNormal><font face=Arial size=2><span style='font-size:10.0pt;
font-family:Arial'>Hi,<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>I saw that there is an option to tell Ipopt that the
Jacobian matrix is constant. But my problem is that almost all my constraints
are linear but very few of them are non linear and involve only one non linear
variable. So, I cannot turn on the jac_constant flag. <o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>My first question is did I have to re-insert constant
elements on the Jacobian even if the new X flag is true or can I use, for
example, a global variable that tell me if the function eval_jac_g is called at
least one time with values !=NULL? <o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>And finally if I turn on the jac_constant (suppose
all my constraints are linear) did the function eval_jac_g will be call only
once with values != NULL for all iterations?<o:p></o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font face=Arial size=2><span lang=EN-CA style='font-size:
10.0pt;font-family:Arial'>Thank you<o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font face=Georgia size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Georgia'>Pascal
Côté, Ph.D. Ing. Jr.<br>
Ingénieur analyste en recherche opérationnelle</span></font><span lang=EN-CA><o:p></o:p></span></p>
<p style='margin-bottom:0cm;margin-bottom:.0001pt'><st1:place w:st="on"><font color=red face=Georgia size=3><span lang=EN-CA style='font-size:12.0pt;
font-family:Georgia;color:red'>Rio</span></font></st1:place><font color=red face=Georgia><span lang=EN-CA style='font-family:Georgia;color:red'> Tinto</span></font><font face=Georgia size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Georgia'>
<font color=red><span style='color:red'>Alcan</span></font><o:p></o:p></span></font></p>
<p style='margin:0cm;margin-bottom:.0001pt'><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'>Énergie électrique</span></font><font face=Georgia size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Georgia'><o:p></o:p></span></font></p>
<p style='margin-top:0cm'><font face=Arial size=2><span lang=EN-CA style='font-size:10.0pt;font-family:Arial'>1954 Davis, <st1:place w:st="on"><st1:City w:st="on">Jo<span lang=FR-CA>nquière</span></st1:City><span lang=FR-CA>, <st1:PostalCode w:st="on">G7S 4R5</st1:PostalCode>, <st1:State w:st="on">QC</st1:State>, <st1:country>Canada</st1:country></span></st1:place><span lang=FR-CA> </span></span></font><font face=Georgia size=2><span style='font-size:10.0pt;font-family:Georgia'><o:p></o:p></span></font></p>
<p><font face="Times New Roman" size=3><span style='font-size:12.0pt'>T: +1
418-699-3860 (3675) F: +1 418-699-3357 </span></font><font face=Georgia size=2><span style='font-size:10.0pt;font-family:Georgia'><o:p></o:p></span></font></p>
<p style='margin-bottom:0cm;margin-bottom:.0001pt'><font face=Arial size=2><span style='font-size:10.0pt;font-family:Arial'><a href="mailto:pascal.cote@riotinto.com" title="mailto:marco.latraverse@riotinto.com">pascal.cote@riotinto.com</a> </span></font><o:p></o:p></p>
<p style='margin-bottom:0cm;margin-bottom:.0001pt'><font face="Times New Roman" size=3><span lang=EN-CA style='font-size:12.0pt'><a href="http://www.riotinto.com/riotintoalcan" title="http://www.riotinto.com/riotintoalcan"><font face=Arial size=2 title="http://www.riotinto.com/riotintoalcan"><span title="http://www.riotinto.com/riotintoalcan"><span lang=FR-CA style='font-size:10.0pt;font-family:Arial'>http://www.riotinto.com/riotintoalcan</span></span></font></a></span><o:p></o:p></font></p>
<p class=MsoNormal><font face="Times New Roman" size=3><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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