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<div><span></span>Hi Gerald,</div><div><br></div><div>I attached the statistics in the attachment. </div><div><br></div><div><span style="font-size: 10.5pt; line-height: 1.5; background-color: window;">Waiting for your reply. </span></div><div><br></div><div>Best regards,</div><div><br></div><div>Kai WEI</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> 2016-03-15 00:30</div><div><b>To:</b> <a href="mailto:weikaimas@163.com">weikaimas@163.com</a></div><div><b>CC:</b> <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="FoxDiv20160315133338930940">
<div class="moz-cite-prefix">Hi Wei Kai,<br>
<br>
could you please print the statistics at the end of the solving
process and send them to me. Probably, you can see there which
propagator did reductions.<br>
<br>
Best,<br>
Gerald<br>
<br>
<br>
On 12.03.2016 06:49, <a class="moz-txt-link-abbreviated" href="mailto:weikaimas@163.com">weikaimas@163.com</a> wrote:<br>
</div>
<blockquote cite="mid:2016031213494287355325@163.com" type="cite" style="margin-top: 0px; margin-bottom: 0px; margin-left: 0.5em;">
<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>
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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 moz-do-not-send="true" href="mailto:gamrath@zib.de">Gerald Gamrath</a></div>
<div><b>Date:</b> 2016-03-04 18:23</div>
<div><b>To:</b> <a moz-do-not-send="true" href="mailto:weikaimas@163.com">weikaimas@163.com</a>; <a moz-do-not-send="true" 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 moz-do-not-send="true" 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; margin-bottom: 0px; margin-left: 0.5em;"> 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>
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</blockquote>
<br>
</div></div></blockquote>
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