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<div class="moz-cite-prefix">Dear Yankai,<br>
<br>
I would use the two limiting parameters for solution number and
objective together:<br>
<br>
set limits objective -1e+17<br>
set limits solutions 1<br>
<br>
The solution limit internally respects the objective limit, and
SCIP correctly stops. You can verify this from the output: (I
solved the example problem check/instances/MIP/bell5.mps):<br>
<br>
<pre>SCIP Status : solving was interrupted [solution limit reached]
Solving Time (sec) : 0.04
Solving Nodes : 1
Primal Bound : +8.98999851950592e+06 (3 solutions, 1 respecting the objective limit)
Dual Bound : +8.95607775334990e+06
</pre>
Happy continuation with your experiments,<br>
Gregor<br>
<pre>
</pre>
<br>
<br>
Am 20.02.2017 um 00:04 schrieb Yankai Cao:<br>
</div>
<blockquote
cite="mid:4B64F0AD-FED9-48E4-BF96-06C52760206B@gmail.com"
type="cite">
<meta http-equiv="Content-Type" content="text/html;
charset=windows-1252">
Hi, Gregor,
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">Thanks for your information. I have search the user
parameters but cannot find the right parameter. </div>
<div class=""><br class="">
</div>
<div class="">I am solving a number of (e.g. 1000) NLPs with
different parameters in the model. Many cases are unbounded.
The following is the output of SCIP for the smallest case:</div>
<div class=""><br class="">
</div>
<div style="margin: 0px; line-height: normal; font-family: 'Andale
Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"
class=""><span style="font-variant-ligatures:
no-common-ligatures" class=""> node | left |LP iter|LP
it/n| mem | dualbound | primalbound | gap </span></div>
<div style="margin: 0px; line-height: normal; font-family: 'Andale
Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"
class=""><span style="font-variant-ligatures:
no-common-ligatures" class=""> 1 | 0 | 1 | -
| 209k| -- |-1.000000e+05 | Inf </span></div>
<div style="margin: 0px; line-height: normal; font-family: 'Andale
Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"
class=""><span style="font-variant-ligatures:
no-common-ligatures" class="">(node 1) LP relaxation is
unbounded (LP 1)</span></div>
<div style="margin: 0px; line-height: normal; font-family: 'Andale
Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"
class=""><span style="font-variant-ligatures:
no-common-ligatures" class=""> 1 | 2 | 4 | -
| 210k| -- |-1.000000e+05 | Inf </span></div>
<div style="margin: 0px; line-height: normal; font-family: 'Andale
Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);"
class=""><span style="font-variant-ligatures:
no-common-ligatures" class="">* 2 | 1 | 6 | 5.0
| 211k| -- |-6.800000e+17 | Inf </span></div>
<div class=""><span style="color: rgb(41, 249, 20); font-family:
'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">100 |</span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">99 | </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">6 | </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">0.1 | 241k|</span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">--</span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">|-6.800000e+17 |</span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class="">Inf</span><span
style="color: rgb(41, 249, 20); font-family: 'Andale Mono';
background-color: rgb(0, 0, 0);" class=""> </span> </div>
<div class=""><br class="">
</div>
<div class="">…</div>
<div class="">
<div style="margin: 0px; line-height: normal; font-family:
'Andale Mono'; color: rgb(41, 249, 20); background-color:
rgb(0, 0, 0);" class="">
<div style="margin: 0px; line-height: normal;" class="">
<div style="margin: 0px; line-height: normal;" class=""><span
style="font-variant-ligatures: no-common-ligatures"
class=""> node | left |LP iter|LP it/n| mem |
dualbound | primalbound | gap </span></div>
<div style="margin: 0px; line-height: normal;" class=""><span
style="font-variant-ligatures: no-common-ligatures"
class=""> 10575k| 9648k| 6 | 0.0 |2501M|
-- |-1.000000e+18 | Inf </span></div>
<div style="margin: 0px; line-height: normal;" class=""><span
style="font-variant-ligatures: no-common-ligatures"
class=""> 10575k| 9648k| 6 | 0.0 |2501M|
-- |-1.000000e+18 | Inf </span></div>
</div>
</div>
</div>
<div class=""><br class="">
</div>
<div class="">As you can see, at node 2, SCIP have already find a
prime bound of -6.8e17, which is so small that I can view it as
unbounded for my model. I want SCIP at node 2 to stop and return
me this prime bound. However, SCIP is still running after
exploring more than 10 million nodes. Setting a solution limit
of 1 is not appropriate for my problem, because the primal bound
in the node 1 is not large enough for me to declare that the
problem is unbounded. </div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">Regard,</div>
<div class="">Yankai</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Feb 17, 2017, at 10:23 AM, Gregor Hendel
<<a moz-do-not-send="true" href="mailto:hendel@zib.de"
class="">hendel@zib.de</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">Hi Yankai,<br class="">
<br class="">
please read the documentation of SCIP, especially search
the limits in the user parameters<br class="">
<br class="">
<a moz-do-not-send="true"
href="http://scip.zib.de/doc/html/PARAMETERS.php"
class="">http://scip.zib.de/doc/html/PARAMETERS.php</a><br
class="">
<br class="">
to find something that matches your purpose. IMHO, there
is nothing to speed up the detection of unboundedness.
What you should rather do, is set up a proper lower
bound for your model, and set a solution limit of 1 to
stop if feasibility of this modified model was proven.<br
class="">
<br class="">
Happy scipping,<br class="">
Gregor<br class="">
<br class="">
<br class="">
<br class="">
Am 17.02.2017 um 17:02 schrieb Yankai Cao:<br class="">
<blockquote type="cite" class="">Dear Benjamin,<br
class="">
<br class="">
<br class="">
Thanks so much for your reply. Is there any parameter
I can set to help SCIP detect if the problem is
unbound. For example, for my model, if SCIP find an
upper bound <= ub (e.g. -1e10), I want SCIP to stop
and declare the problem is unbound. Otherwise, it will
takes SCIP much much more time to continue. Thanks.<br
class="">
<br class="">
<br class="">
Regards,<br class="">
Yankai<br class="">
<br class="">
<br class="">
<blockquote type="cite" class="">On Feb 17, 2017, at
7:19 AM, Benjamin Müller
<a class="moz-txt-link-rfc2396E" href="mailto:benjamin.mueller@zib.de"><benjamin.mueller@zib.de></a> wrote:<br class="">
<br class="">
Dear Yankai,<br class="">
<br class="">
you can use<br class="">
<br class="">
<span class="Apple-tab-span" style="white-space:pre"> </span>set/limits/objective<br
class="">
<br class="">
in order to set an objective limit. SCIP will then
only look for solutions that have a better value
than the given objective limit. You can think of it
as an artificial upper bound for your (minimization)
problem.<br class="">
<br class="">
As far as I can see it, there is no parameter to set
an initial dual bound in SCIP. There is
SCIPupdateLocalDualbound in the API that could be
called during the SCIP_STAGE_PROBLEM stage.<br
class="">
<br class="">
Regards,<br class="">
Benjamin<br class="">
<br class="">
<br class="">
On 02/17/2017 07:24 AM, Yankai Cao wrote:<br
class="">
<blockquote type="cite" class="">Hi, All,<br
class="">
<br class="">
I am new to SCIP. I want to know how to set a
parameter ub (e.g. -1e10) so that if SCIP find
the upper bound is smaller than ub SCIP can stop
and declare that the problem is unbounded?<br
class="">
<br class="">
Also, how to provide known upper/lower bounds
before b&b, which might help speed the
solution time of SCIP?<br class="">
<br class="">
Thanks very much!<br class="">
<br class="">
<br class="">
Regards,<br class="">
Yankai<br class="">
<br class="">
<br class="">
_______________________________________________<br
class="">
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class="">
<br class="">
</blockquote>
-- <br class="">
______________________________<br class="">
Benjamin Müller<br class="">
Zuse Institute Berlin<br class="">
Takustr. 7, 14195 Berlin<br class="">
<a class="moz-txt-link-abbreviated" href="mailto:benjamin.mueller@zib.de">benjamin.mueller@zib.de</a><br class="">
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</blockquote>
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