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<div class="moz-cite-prefix">Dear Nalan,<br>
<br>
Mahdi's mail didn't reach the mailing list, because he also sent
it from a mail address not registered for the list.<br>
<br>
It seems like your problem is not caused by the branching, on two
of the three log file, you already stop before the first branching
is performed.<br>
<br>
If you could print the statistics after stopping and send the log
files again, this would help us a lot to identify the problem.<br>
<br>
Did you change all constraints to modifiable to which you add
variables during solving? Otherwise, propagation might fix some of
your priced variables to 0 and it might happen that pricing
regenerates them again and again. Except for that, my best guess
would be that you somehow compute the reduced cost wrongly.<br>
<br>
Best,<br>
Gerald<br>
<br>
<br>
On 01.04.2014 09:20, Gulpinar, Nalan wrote:<br>
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<p><span style="font-size: 12pt;">Dear Ambros, </span><br>
</p>
<div style="color: #282828;">
<div>
<div style="font-size: 12pt; color: #000000;
background-color: #ffffff; font-family: calibri, arial,
helvetica, sans-serif;">
<p><br>
</p>
<p>Thank you for your prompt reply. As you suggested, I am
resending my previous email. <br>
</p>
<p><br>
</p>
<p>I am writing this email about the problem we have faced
with SCIP. <br>
</p>
<p><span style="font-size: 12pt;">As Mahdi reported
yesterday (please </span><span style="font-size:
12pt;">s</span><span style="font-size: 12pt;">ee his
email </span><span style="font-size: 12pt;">b</span><span
style="font-size: 12pt;">elow), we have checked the </span><br>
</p>
<p>code several <span style="font-size: 12pt;">times, and
even t</span><span style="font-size: 12pt;">rie</span><span
style="font-size: 12pt;">d</span><span
style="font-size: 12pt;"> to run its alternative
formulation but the problem </span></p>
<p><span style="font-size: 12pt;"></span><span
style="font-size: 12pt;">remains the </span><span
style="font-size: 12pt;">same. I have also attached
the output of three instances of the model. </span></p>
<p><span style="font-size: 12pt;">I hope </span><span
style="font-size: 12pt;">this helps you to identify
the problem. </span></p>
<p><span style="font-size: 12pt;"><br>
We use column generation procedure where continuous
variables are added into the </span></p>
<p><span style="font-size: 12pt;">master problem and
branch and bound procedure is used to solve the master
problem. </span></p>
<p><span style="font-size: 12pt;">But after some
iterations it cannot be improved. For example, as you
will see from </span></p>
<p><span style="font-size: 12pt;">log file.rtf, we have
the following output. </span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;">I am looking forward to receiving your reply
and suggestions. </span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;"><br>
</span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;">Thank you for your help at advance. </span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;"><br>
</span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;">Best regards</span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;"><br>
</span></p>
<p style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;"><span style="font-size:
12pt;">Nalan </span></p>
<div style="font-family: calibri, arial, helvetica,
sans-serif; font-size: 16px;">
<p><br>
</p>
<div style="font-family: tahoma; font-size: 13px;">_____________________________________________<br>
Nalan Gulpinar, Ph.D. <br>
Associate Professor of Operational Research<br>
Warwick Business School<br>
The University of Warwick, Coventry, CV4 7AL, UK.<br>
Tel: +44 (0) 24 7652 4491<br>
Fax: +44 (0) 24 7652 4539<br>
Email: <a class="moz-txt-link-abbreviated" href="mailto:Nalan.Gulpinar@wbs.ac.uk">Nalan.Gulpinar@wbs.ac.uk</a><br>
_____________________________________________<br>
</div>
</div>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="color: #20124d; font-family: georgia,
serif;">leastJ/leastT= 0,0, minRedCost: -43.3</span><span
style="color: #20124d; font-family: georgia, serif;">117</span><span
style="font-size: 12pt;"><br>
</span></p>
<div style="font-size: 16px; background-color: #ffffff;
font-family: georgia, serif; color: #20124d;">
<p>total cost= 1173.06, 10.84, 882.22, 280, z_134</p>
<p>134, add new variables</p>
<p> 0.1s| 1 | 0 | 203 | - | 725k| 0 |
33 | 206 | 115 | 205 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> time | node | left |LP iter|LP it/n| mem |mdpt
|frac |vars |cons |cols |rows |cuts |confs|strbr|
dualbound | primalbound | gap
</p>
<p> 0.1s| 1 | 0 | 205 | - | 725k| 0 |
36 | 206 | 115 | 206 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> </p>
<p> leastJ/leastT= 2,0, minRedCost: -90.6829</p>
<p>total cost= 532.45, 1.05, 363.4, 168, z_135</p>
<p>135, add new variables</p>
<p> 0.1s| 1 | 0 | 205 | - | 727k| 0 |
36 | 207 | 115 | 206 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> 0.1s| 1 | 0 | 205 | - | 727k| 0 |
23 | 207 | 115 | 207 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> </p>
<p> leastJ/leastT= 2,0, minRedCost: -90.6829</p>
<p>total cost= 532.45, 1.05, 363.4, 168, z_136</p>
<p>136, add new variables</p>
<p> 0.1s| 1 | 0 | 205 | - | 729k| 0 |
23 | 208 | 115 | 207 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> 0.1s| 1 | 0 | 209 | - | 729k| 0 |
23 | 208 | 115 | 208 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> </p>
<p> leastJ/leastT= 1,0, minRedCost: -88.4043</p>
<p>total cost= 350.84, 31.14, 151.7, 168, z_137</p>
<p>137, add new variables</p>
<p> 0.1s| 1 | 0 | 209 | - | 731k| 0 |
23 | 209 | 115 | 208 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> </p>
<p> leastJ/leastT= 1,0, minRedCost: -88.4043</p>
<p>total cost= 350.84, 31.14, 151.7, 168, z_138</p>
<p>138, add new variables</p>
<p> 0.1s| 1 | 0 | 209 | - | 733k| 0 |
23 | 210 | 115 | 208 | 115 | 0 | 0 | 0 |
-- | 7.654555e+03 | Inf
</p>
<p> </p>
<p> leastJ/leastT= 1,0, minRedCost: -88.4043</p>
<p>total cost= 350.84, 31.14, 151.7, 168, z_139</p>
<p>139, add new variables<br>
</p>
<br>
This goes on......<br>
</div>
<div style="color: #282828;">
<div id="divRplyFwdMsg" dir="ltr">
<div> <br>
</div>
</div>
<div>
<div dir="ltr">
<div class="gmail_quote">
<div class="HOEnZb">
<div class="h5">
<div dir="ltr"><br>
<div class="gmail_quote">----------
Forwarded message ----------<br>
From: <b class="gmail_sendername">mahdi
noorizadegan</b> <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:m.noorizadegan@gmail.com"
target="_blank">m.noorizadegan@gmail.com</a>></span><br>
Date: 31 March 2014 18:37<br>
Subject: Column generation<br>
To: <a moz-do-not-send="true"
href="mailto:Scip@zib.de"
target="_blank">Scip@zib.de</a><br>
<div dir="ltr">
<div style="font-family: georgia, serif;
color: #20124d;"><br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">Hi,<br>
<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">I have been trying to
solve a problem by the column
generation method.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">The variables which
are being added to the master problem
were binary<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">so I had the problem
with the branch and bound procedure.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">I changed the
formulation and added new dummy binary
variables and changed<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">the type of the other
variables to continuous.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">So there should not
be any problem with the branch and
bound producer.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">However, I still have
problems. It keeps adding the same
column after few iterations!<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">For example for a
simple instance, the objective
function value is 350.84,<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">the dual value is
439.24 therefore the reduced cost is
-439.24+350.84=-88.40.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">When this new
variable is added to the problem, in
the next iteration this variable is
again
<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">identified and added!<br>
<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">I have checked the
pricing problem. It seems correct and
I could not find any mistake.<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">I was wondering if
you could help me and let me know what
can be wrong!?<br>
<br>
</div>
<div style="font-family: georgia, serif;
color: #20124d;">Thanks and best,<br>
Mahdi<br>
</div>
</div>
</div>
<br>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
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