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<div class="moz-cite-prefix">Aleksandr,<br>
<br>
In this problem, during normal solves the code is spending too
much time before declaring a branch to be infeasible - I may try
and see if I can improve.<br>
<br>
However this error is to do with strong branching. Then the code
is trying to be as fast as possible and may miss some checks.
This does not matter too much as it will just declare that
tentative branch to be unfinished. This is because it is only
doing a hundred or so iterations. This maximum number of
iterations<br>
is preset to a high value, but the standalone solver and other
implementations reduce this to a reasonable value by <br>
<br>
solver->setIntParam(OsiMaxNumIterationHotStart, 100);<br>
<br>
I will look into why a strong branch "looped" - and did 9999999
iterations! For now use above setting or similar.<br>
<br>
John Forrest<br>
On 09/12/17 23:12, Aleksandr M. Kazachkov wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CABsukBnbv4NUj-=N_zM=n4H-w2oty5KOg3hp5hoGt2n6h0RVjg@mail.gmail.com">
<div dir="ltr">Hello all,<br>
<br>
On my computer, Cbc-2.9 (latest stable, compiled with lapack,
blas, and enable_debug on) takes an unusually long time (~15
minutes) on a particular node of the branch-and-bound tree for a
version of the instance pigeon-13 from MIPLIB (after applying
some preprocessing to it). The instance is here:<br>
<br>
<a
href="https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_17CWEN1A5ZefhAEZsUwnU1gJl-5FEPM9d5b_view-3Fusp-3Dsharing&d=DwMFaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=js2M0T-3OIMIVDvokcKjokJbk0F8QOCd0mT4FsVFE88&m=4sql7feDwXVnADRe81wH9Kinl4oVnVLekMxeZUOQrx8&s=4kM-ZvXu57rNQKxU50jfoQ66IprD2kkjH0k3oyZALY8&e="
moz-do-not-send="true">https://drive.google.com/file/d/17CWEN1A5ZefhAEZsUwnU1gJl_EPM9d5b/view?usp=sharing</a><br>
<br>
I am reporting this in case the behavior is the result of a bug,
though it may simply be a case in which I should be using
different settings. On my system, the following lines of code
reproduce the behavior:<br>
<br>
OsiClpSolverInterface* solver = new OsiClpSolverInterface;<br>
solver->readMps("pigeon-13_presolved.mps.gz");<br>
CbcModel* cbc_model = new CbcModel;<br>
cbc_model->swapSolver(solver);<br>
cbc_model->setModelOwnsSolver(true); // solver will be
deleted with cbc object<br>
cbc_model->setLogLevel(3);<br>
cbc_model->messagesPointer()->setDetailMessages(10, 10000,
(int *) NULL);<br>
cbc_model->setPrintFrequency(1);
<div>cbc_model->setMaximumNodes(656); // at least on my
system, this will show the slow node<br>
<div>cbc_model->branchAndBound(3);<br>
<br>
As indicated in the log (excerpt below), Cbc stalls for
quite a while after 654 nodes.
<div><br>
Cbc0010I After 654 nodes, 44 on tree, 1e+50 best solution,
best possible -13000 (84.18 seconds)<br>
Clp0006I 0 Obj -13000 Primal inf 0.1871137 (1)<br>
Clp0006I 2 Obj -13000<br>
Clp0000I Optimal - objective value -13000</div>
<div>---- long stall here ---</div>
<div>Cbc0007I Strong branching on 145 (184), down 0 (20) up
6.4595608e+14 (19) value 0.5<br>
Cbc0007I Strong branching on 179 (218), down 3.6850268e+13
(12) up 0 (20) value 0.5<br>
Node 655 depth 45 unsatisfied 22 sum 1.40366e+15 obj
-13000 guess -12708 branching on 184<br>
Cbc0015I Node 655 Obj -13000 Unsat 22 depth 45<br>
Cbc0010I After 655 nodes, 44 on tree, 1e+50 best solution,
best possible -13000 (1015.90 seconds)<br>
Clp0006I 0 Obj -13000 Primal inf 0.10206197 (1)<br>
Clp0006I 5 Obj -13000<br>
Clp0000I Optimal - objective value -13000</div>
</div>
</div>
<div><br>
</div>
<div>If there is any other information that would be helpful
that I can provide, please let me know,</div>
<div>Aleksandr Kazachkov</div>
</div>
<br>
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<br>
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