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<div><span></span>Dear Gerald,</div><div><br></div><div>I have tried to use <span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">SCIPchgVarUbLazy() to set an upper bound value for each variable in 3.2.0 and use version 3.2.1. </span></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">However, I also found some variables with negative reduced cost in both above methods. The number of negative </span><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;"> </span><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">reduced cost variable </span></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">is much less than version 3.2.0 without </span><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">SCIPchgVarUbLazy(), and both new methods have the some results.</span></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;"><br></span></div><div>Would have some methods to avoid the this phenomenon because the pricing method will find some useless variables.</div><div><span style="font-family: 'Microsoft YaHei UI', Tahoma; font-size: 10.5pt; line-height: 1.5; background-color: window;"><br></span></div><div><span style="font-family: 'Microsoft YaHei UI', Tahoma; font-size: 10.5pt; line-height: 1.5; background-color: window;">Best regards,</span></div><div><span style="font-family: 'Microsoft YaHei UI', Tahoma; font-size: 10.5pt; line-height: 1.5; background-color: window;">Kai Wei</span></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;"><br></span></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;"><br></span></div><div><br></div><div><br></div>
<blockquote style="margin-top: 0px; margin-bottom: 0px; margin-left: 0.5em;"><div> </div><div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm"><div style="PADDING-RIGHT: 8px; PADDING-LEFT: 8px; FONT-SIZE: 12px;FONT-FAMILY:tahoma;COLOR:#000000; BACKGROUND: #efefef; PADDING-BOTTOM: 8px; PADDING-TOP: 8px"><div><b>From:</b> <a href="mailto:gamrath@zib.de">Gerald Gamrath</a></div><div><b>Date:</b> 2016-03-04 18:23</div><div><b>To:</b> <a href="mailto:weikaimas@163.com">weikaimas@163.com</a>; <a href="mailto:scip@zib.de">scip</a></div><div><b>Subject:</b> Re: Reduced cost about variables in LP relaxation</div></div></div><div><div class="FoxDiv20160312131757072986">
<div class="moz-cite-prefix">Dear Wei Kai,<br>
<br>
if a variable has an upper bound and is nonbasic at its upper
bound in the LP solution, it may have negative reduced cost.<br>
<br>
Did you set an upper bound for your variables? If so, you can use
SCIPchgVarUbLazy() to set an upper bound value which is implicitly
given by the constraints and should not explicitly added to the LP
as bound of the variable.<br>
<br>
However, we also noticed that some propagators installed upper
bound on variables in branch-and-price applications. Although the
reductions were correct, they may lead to troubles as you are now
observing them. Therefore, these propagators are now automatically
disabled if pricers are active. This fix is already included in
the bugfix version 3.2.1 released earlier this week. Please try if
updating your version fixes your issues.<br>
<br>
Best,<br>
Gerald<br>
<br>
On 04.03.2016 08:56, <a class="moz-txt-link-abbreviated" href="mailto:weikaimas@163.com">weikaimas@163.com</a> wrote:<br>
</div>
<blockquote cite="mid:2016030415555871994824@163.com" type="cite" style="margin-top: 0px;">
Hi
all,
<div><br>
</div>
<div> I have used SCIP to implement a B&P procedure. At leaf
nodes, before I implement pricing algorithm I use
SCIPgetVarRedcosr()</div>
<div>to check the reduced cost of all variables (<span style="font-size: 10.5pt; line-height: 1.5; background-color:
window;">SCIPgetLPSolstat() returns 1</span><span style="font-size: 10.5pt; line-height: 1.5; background-color:
window;">). I found some variables with negative reduced cost.</span></div>
<div><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;"> Can you give me the reasons about
</span><span style="font-size: 10.5pt; line-height: 1.5;
background-color: window;">this phenomenon? How can I avoid
to find the variables with negative reduced cost in my pricing
algorithm?</span></div>
<div><br>
</div>
<div><span style="font-family: 'Microsoft YaHei UI', Tahoma;
line-height: normal;">Best regards,</span></div>
<div><span style="font-family: 'Microsoft YaHei UI', Tahoma;
line-height: normal;"><br>
</span></div>
<div><span style="font-family: 'Microsoft YaHei UI', Tahoma;
line-height: normal;">Kai WEI</span></div>
<div><br>
</div>
</blockquote>
<br>
</div></div></blockquote>
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