<html>
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Courier;
panose-1:2 7 4 9 2 2 5 2 4 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";}
p.MsoAutoSig, li.MsoAutoSig, div.MsoAutoSig
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
span.EmailStyle17
{font-family:Arial;
color:black;
font-weight:normal;
font-style:normal;
text-decoration:none none;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'>Hello,</span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'> </span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'>We’ve been exploring IPOPT (Fortran
version) for some time in solving our nonlinear programming problem and ran
into a curious behavior. We’re in the unfortunate position of
having to set DTOL rather large and we’ve noticed that the barrier
parameter is hard-bounded by DTOL/10. In your paper, you explain: “the
update (7) does not allow the rule to become smaller than necessary given the
desired tolerance \epsilon_{tol}, thus avoiding numerical difficulties at the
end of the optimization procedure.” We are unclear on what the specific
numerical difficulties would be for this primal-dual formulation of the
problem. Are there any results that have shown what the ‘necessary’
value of MU should be in relation to the overall tolerance?</span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'> </span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'>Since I have you attention I can’t
resist asking if there are any updates on when the C++ alpha version will be
released?</span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'> </span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'>Regards,</span></font></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:black'> </span></font></p>
<p class=MsoAutoSig><font size=2 color=black face=Arial><span lang=PT-BR
style='font-size:10.0pt;font-family:Arial;color:black'>--Ivan.</span></font></p>
<p class=MsoAutoSig><font size=3 color=black face="Times New Roman"><span
lang=PT-BR style='font-size:12.0pt;color:black'> </span></font></p>
<p class=MsoAutoSig><font size=2 color=black face=Courier><span lang=PT-BR
style='font-size:10.0pt;font-family:Courier;color:black'>----------------------------</span></font></p>
<p class=MsoAutoSig><font size=2 color=black face=Courier><span lang=PT-BR
style='font-size:10.0pt;font-family:Courier;color:black'>Ivan B. Oliveira</span></font></p>
<p class=MsoAutoSig><font size=2 color=black face=Courier><span lang=PT-BR
style='font-size:10.0pt;font-family:Courier;color:black'>SC12-205</span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Courier><span
style='font-size:10.0pt;font-family:Courier;color:black'>(408)765-0584</span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
</div>
</body>
</html>