<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">Hi Gerald,<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><o:p style="background-color: rgba(255, 255, 255, 0);"> </o:p></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">as you suggested, I changed the SCIP source so that the pricer can be deactivated in solving state. For that I adapted these lines:<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><o:p style="background-color: rgba(255, 255, 255, 0);"> </o:p></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">scip_pricer.c (line 480): SCIP_CALL( SCIPcheckStage(scip,"SCIPdeactivatePricer", FALSE, TRUE, FALSE, FALSE,FALSE, FALSE, FALSE, FALSE, FALSE, 1, FALSE, TRUE,FALSE, FALSE) );<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);"> </span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">pricer.c (line 370): assert(set->stage == SCIP_STAGE_PROBLEM || set->stage == SCIP_STAGE_SOLVING); // (Also == SCIP_STAGE_PROBLEM should be allowed?)<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);"> </span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">This changes make the concept work as planned, without any problems so far.<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><o:p style="background-color: rgba(255, 255, 255, 0);"> </o:p></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">Best,<o:p></o:p></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0.0001pt;"><span style="background-color: rgba(255, 255, 255, 0);">Jan</span></p><br><div dir="ltr"><br></div><div dir="ltr"><br>Am 26.07.2019 um 21:13 schrieb Gerald Gamrath <<a href="mailto:gamrath@zib.de">gamrath@zib.de</a>>:<br><br></div><blockquote type="cite"><div dir="ltr">
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Hi Jan,<br>
<br>
ok, I did not check that. I guess it should be no problem if you
change the checkStage call in SCIPdeactivatePricer() to allow
calling the method also in solving stage. (and by the way, good to
hear that you are using the debug mode first! :-))<br>
<br>
If you don't mind changing the SCIP source, that's the way to go,
and if it works for you in the end, we can change this in the next
release as well. Otherwise, I fear you need to go for solution 1),
where this should not be a problem as you can just tell SCIP to not
copy the pricer. In that case, you need to copy the solution of the
sub-SCIP back to the original SCIP, see any sub-MIP heuristic (e.g.,
rens) for how this can be done.<br>
<br>
The solved stage is only reached when the problem is solved to
optimality (because SCIP otherwise allows you to just continue
solving also after it was already stopped ). You should not go back
to the problem stage, because the priced variables would then be
lost.<br>
<br>
Best,<br>
Gerald<br>
<br>
<br>
<div class="moz-cite-prefix">Am 26.07.19 um 21:02 schrieb
<a class="moz-txt-link-abbreviated" href="mailto:berlingjan@gmail.com">berlingjan@gmail.com</a>:<br>
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<blockquote type="cite" cite="mid:A3FB6C88-D6CC-4EC1-A2D7-41F8BD452ECD@gmail.com">
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<div dir="ltr"><span></span></div>
<div dir="ltr">Hi Gerald,
<div><br>
</div>
<div>I went for solution 2) to disable the pricer and to restart
scip. The problem is that the pricer can only be disabled when
scip is in stage problem or in stage solved and I could not
manage to reach these stages from the pricer. In scip, time
limit is reached but even though after the SCIPsolve() is
finished, scip is in stage solving. How could scip reach stage
solved? Is it necessary that the problem is solved to
optimality? Could we go back to stage problem? <br>
<br>
<div dir="ltr">Best,</div>
<div dir="ltr">Jan</div>
<div dir="ltr"><br>
Am 25.07.2019 um 21:29 schrieb Gerald Gamrath <<a href="mailto:gamrath@zib.de" moz-do-not-send="true">gamrath@zib.de</a>>:<br>
<br>
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Hi Jan,<br>
<br>
there are two options that you already mentioned which I
would suggest as well, but I did not try them myself:<br>
<br>
1) copy the problem using SCIPcopy(), where you can set
copypricers to FALSE. Additionally, you need to loop over
all constraints in the subscip once and set them to be not
modifiable via SCIPsetConsModifiable(). SCIP can only
perform very few presolving, propagation, and separation
steps if constraints are marked to be modifiable, because
in that case, SCIP needs to assume that new variables will
be added to the constraint later which might conflict with
the reductions performed now.<br>
<br>
2) Again, set all constraint to be non-modifiable, disable
the pricer, and then perform a restart and solve the
problem.<br>
<br>
In both cases, you potentially need to re-enable features
that you disabled for the column generation phase.<br>
<br>
I would probably go for the second option first, because
it should be easier to implement, but I am not sure if
perhaps some flags can still be set incorrectly in that
case. If you still observe considerable differences,
please write again.<br>
<br>
Best,<br>
Gerald<br>
<br>
<div class="moz-cite-prefix">Am 24.07.19 um 18:54 schrieb
Jan Berling:<br>
</div>
<blockquote type="cite" cite="mid:CAPeMmq0TTGyT3s6s-WSUTqYX6GAbWyzh5rNYmELFUxrkrLDK8g@mail.gmail.com">
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<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">Dear
SCIP community,<span></span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><span> </span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">I
have a binary optimization problem which uses column
generation, i. a. because adding all variables is
not possible due to memory limitations. However,
solving takes a lot of time and so pricing is
stopped<span> </span>when a timelimit is exceeded,
by setting the result pointer to SCIP_SUCCESS<span style="font-size:9.5pt;font-family:Consolas;color:black">.</span><span></span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><span> </span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">SCIP
continues solving the “final restricted master
problem” but this takes a lot of time.<span></span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><span> </span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">I
made an experiment giving the final transformed lp
file to out-of-the-box-SCIP and the problem is
solved more quickly, due to presolvers and cutting
planes.<span></span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><span> </span></p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">Is
it possible to restart the solving of the
transformed problem after pricing is stopped and to
enable presolving/cutting-planes (e.g. by copying
the problem, enabling presolvers, restarting,
setting SCIP stage...)?</p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><br>
</p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">Kind
regards,</p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif"">Jan<br>
</p>
<p class="MsoNormal" style="margin:0cm 0cm
0.0001pt;font-size:11pt;font-family:"Calibri","sans-serif""><span></span></p>
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