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Dear Jonathan,<br>
<br>
sorry, I now realized that SCIP does not only run into the time
limit but also gets stuck at node 415. I will have a deeper look at
the problem and write a mail if I figured out the problem.<br>
<br>
<br>
Best,<br>
<br>
Benny<br>
<br>
<div class="moz-cite-prefix">On 07/02/2015 09:08 AM, Benjamin Müller
wrote:<br>
</div>
<blockquote cite="mid:5594E351.6000705@zib.de" type="cite">
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Dear Jonathan,<br>
<br>
the problem is that the LP relaxation of this problem is unbounded
and SCIP has some troubles to find a bounded (linear) one. It
would definitely help if you give your variables some artificial
bounds. I tried to replace infinity by M (=1000) and solved the
problem in 2s and got as solution <br>
<br>
<br>
objective value: -0.250000756970904<br>
t_xvar0 0.793669420214128 (obj:0)<br>
t_xvar1 0.707148562806428 (obj:0)<br>
t_xvar2 0.529706057231088 (obj:0)<br>
t_xvar3 0.840921294489214 (obj:0)<br>
t_nlobj -0.250000756970904 (obj:1)<br>
nlreform0 0.62991145338235 (obj:0)<br>
nlreform1sp 0.499941002617224 (obj:0)<br>
nlreform2 0.66741358081024 (obj:0)<br>
nlreform3 0.374581225460006 (obj:0)<br>
<br>
which is far away from M for each variable. Maybe you find some
artificial bounds which are fine for your purposes.<br>
<br>
<br>
Best regards,<br>
<br>
Benny<br>
<br>
<br>
<div class="moz-cite-prefix">On 07/02/2015 02:31 AM, Jonathan
Currie wrote:<br>
</div>
<blockquote
cite="mid:6588F6A32DCF6A498DAD108D389A15E79AA41870@Patterson.autuni.aut.ac.nz"
type="cite">
<pre wrap="">Hi All,
The attached problem hangs (well, fails to make any reasonable progress) in my latest build of SCIP v3.2 with default settings. Original problem:
Min -x(1)*x(2)*x(3)*x(4)
s.t. x(1)^3 + x(2)^2 - 1 == 0
x(1)^2*x(4) - x(3) == 0
x(4)^2 - x(2) == 0
Any ideas?
Thanks,
Jonathan
SCIP: Solving Constraint Integer Programs [v3.2.0, Built Jul 2 2015, VS2013]
- SoPlex [v220] (ZIB Academic License)
- Ipopt [v3.12.3] (Eclipse Public License)
- CppAD [v20140000.3] (Eclipse Public License)
presolving:
(round 1, fast) 0 del vars, 0 del conss, 0 add conss, 1 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
(round 2, fast) 0 del vars, 0 del conss, 0 add conss, 2 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
(round 3, fast) 0 del vars, 0 del conss, 4 add conss, 2 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
(round 4, fast) 0 del vars, 0 del conss, 4 add conss, 3 chg bounds, 0 chg sides, 0 chg coeffs, 7 upgd conss, 0 impls, 0 clqs
(round 5, fast) 0 del vars, 0 del conss, 4 add conss, 4 chg bounds, 0 chg sides, 0 chg coeffs, 8 upgd conss, 0 impls, 0 clqs
presolving (6 rounds: 6 fast, 1 medium, 1 exhaustive):
0 deleted vars, 0 deleted constraints, 4 added constraints, 4 tightened bounds, 0 added holes, 0 changed sides, 0 changed coefficients
0 implications, 0 cliques
presolved problem has 9 variables (0 bin, 0 int, 0 impl, 9 cont) and 8 constraints
2 constraints of type <abspower>
6 constraints of type <quadratic>
Presolving Time: 0.00
time | node | left |LP iter|LP it/n| mem |mdpt |frac |vars |cons |cols |rows |cuts |confs|strbr| dualbound | primalbound | gap
0.0s| 1 | 0 | 0 | - | 219k| 0 | - | 9 | 8 | 9 | 10 | 0 | 0 | 0 | -- | -- | Inf
******************************************************************************
This program contains Ipopt, a library for large-scale nonlinear optimization.
Ipopt is released as open source code under the Eclipse Public License (EPL).
For more information visit <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://projects.coin-or.org/Ipopt">http://projects.coin-or.org/Ipopt</a>
******************************************************************************
0.1s| 1 | 0 | 2 | - | 223k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- | -- | Inf
(node 1) LP relaxation is unbounded (LP 1)
q 0.1s| 1 | 0 | 15 | - | 225k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
0.1s| 1 | 0 | 15 | - | 225k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
(node 1) LP relaxation is unbounded (LP 4)
0.1s| 1 | 2 | 15 | - | 224k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
y 0.1s| 2 | 1 | 15 | 13.0 | 224k| 1 | - | 9 | 8 | 0 | 0 | 1 | 0 | 0 | -- |-2.500000e-001 | Inf
0.2s| 100 | 77 | 40 | 0.4 | 254k| 77 | - | 9 | 8 | 9 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
0.2s| 200 | 45 | 40 | 0.2 | 259k| 112 | - | 9 | 8 | 0 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
0.3s| 300 | 65 | 40 | 0.1 | 273k| 171 | - | 9 | 8 | 9 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
0.3s| 400 | 153 | 555 | 1.4 | 372k| 255 | 0 | 9 | 8 | 9 | 79 | 574 | 0 | 0 | -- |-2.500000e-001 | Inf
SCIP Status : solving was interrupted [time limit reached]
Solving Time (sec) : 1000.00
Solving Nodes : 415
Primal Bound : -2.50000000000035e-001 (2 solutions)
Dual Bound : -1.00000000000000e+020
Gap : infinite
</pre>
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
______________________________
Benjamin Müller
Zuse Institute Berlin
Takustr. 7, 14195 Berlin
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:benjamin.mueller@zib.de">benjamin.mueller@zib.de</a>
+49 30 841 85-195</pre>
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<br>
<pre wrap="">_______________________________________________
Scip mailing list
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
______________________________
Benjamin Müller
Zuse Institute Berlin
Takustr. 7, 14195 Berlin
<a class="moz-txt-link-abbreviated" href="mailto:benjamin.mueller@zib.de">benjamin.mueller@zib.de</a>
+49 30 841 85-195</pre>
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