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<div class="moz-cite-prefix">Jean-Paul,<br>
<br>
There is an opaque option tunePreprocess - the default is 6 which
says something about looking for SOS >=6. However it can
influence number of passes. So try setting it to 2006 and see
what effect that has.<br>
<br>
Looking at log, it is interesting that last two passes fix a lot
of variables but does no substitutions. If that coding is only
switched after end of substitutions it may be possible to redo the
code to make faster.<br>
<br>
If you send me a sample, I can see why it is so slow.<br>
<br>
John<br>
<br>
<br>
<br>
On 24/01/13 14:31, Watson, Jean-paul wrote:<br>
</div>
<blockquote
cite="mid:4FD66F25D7BD5F438E839BBA5F76409530073110@EXMB02.srn.sandia.gov"
type="cite">
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<div>Hi all,</div>
<div><br>
</div>
<div>I have a medium-scale MIP that is behaving badly when I try
to solve it with CBC. In particular, it takes around 5+ minutes
just to get to the point where the feasibility pump kicks in
(which turns out to quickly find an optimal solution). This is
in contrast to GLPK, SCIP, CPLEX, Gurobi, etc., which get to
this point in a few seconds at worst. The output trace is
below. </div>
<div><br>
</div>
<div>The vast majority of the time is spent doing substitutions /
variable fixing. Is there an option to either turn such
processing off, or reduce the number of passes? I tried turning
off all cuts and presolve, and didn't see any other options that
were obvious (at least to me). </div>
<div><br>
</div>
<div>Thanks!</div>
<div><br>
</div>
<div>Jean-Paul</div>
<div><br>
</div>
<div>---</div>
<div><br>
</div>
<div>
<div>command line - cbc foo.lp (default strategy 1)</div>
<div>Coin0009I CoinLpIO::readLp(): Maximization problem
reformulated as minimization</div>
<div>Continuous objective value is -53.7 - 0.66 seconds</div>
<div>Cgl0002I 542 variables fixed</div>
<div>Cgl0003I 188 fixed, 0 tightened bounds, 0 strengthened
rows, 58122 substitutions</div>
<div>Cgl0003I 99 fixed, 0 tightened bounds, 0 strengthened rows,
42070 substitutions</div>
<div>Cgl0003I 69 fixed, 0 tightened bounds, 0 strengthened rows,
41920 substitutions</div>
<div>Cgl0003I 72 fixed, 0 tightened bounds, 0 strengthened rows,
41792 substitutions</div>
<div>Cgl0003I 51 fixed, 0 tightened bounds, 0 strengthened rows,
41672 substitutions</div>
<div>Cgl0003I 75 fixed, 0 tightened bounds, 0 strengthened rows,
41528 substitutions</div>
<div>Cgl0003I 66 fixed, 0 tightened bounds, 0 strengthened rows,
41406 substitutions</div>
<div>Cgl0003I 72 fixed, 0 tightened bounds, 0 strengthened rows,
41258 substitutions</div>
<div>Cgl0003I 63 fixed, 0 tightened bounds, 0 strengthened rows,
41118 substitutions</div>
<div>Cgl0003I 2320 fixed, 0 tightened bounds, 0 strengthened
rows, 0 substitutions</div>
<div>Cgl0003I 2324 fixed, 0 tightened bounds, 0 strengthened
rows, 2 substitutions</div>
<div>Cgl0003I 0 fixed, 0 tightened bounds, 0 strengthened rows,
1 substitutions</div>
<div>Cgl0004I processed model has 777 rows, 6796 columns (6795
integer) and 17610 elements</div>
<div>Cbc0038I Pass 1: suminf. 0.00000 (0) obj. -25
iterations 938</div>
<div>Cbc0038I Solution found of -25</div>
<div>Cbc0038I Before mini branch and bound, 6715 integers at
bound fixed and 0 continuous</div>
<div>Cbc0038I Full problem 777 rows 6796 columns, reduced to 20
rows 20 columns</div>
<div>Cbc0038I Mini branch and bound improved solution from -25
to -27 (840.93 seconds)</div>
<div>Cbc0038I Round again with cutoff of -27.065</div>
<div>Cbc0038I Pass 2: suminf. 1.30018 (16) obj. -27.065
iterations 475</div>
<div>Cbc0038I Pass 3: suminf. 1.04014 (16) obj. -27.065
iterations 89</div>
<div>Cbc0038I Pass 4: suminf. 1.04014 (14) obj. -27.065
iterations 612</div>
<div>Cbc0038I Pass 5: suminf. 0.91013 (14) obj. -27.065
iterations 72</div>
<div>Cbc0038I Pass 6: suminf. 0.91013 (12) obj. -27.065
iterations 536</div>
<div>Cbc0038I Pass 7: suminf. 0.78011 (12) obj. -27.065
iterations 55</div>
<div>Cbc0038I Pass 8: suminf. 1.04014 (12) obj. -27.065
iterations 528</div>
<div>Cbc0038I Pass 9: suminf. 0.78011 (12) obj. -27.065
iterations 239</div>
<div>Cbc0038I Pass 10: suminf. 0.91013 (12) obj. -27.065
iterations 529</div>
<div>Cbc0038I Pass 11: suminf. 0.78011 (11) obj. -27.065
iterations 85</div>
<div>Cbc0038I Pass 12: suminf. 1.30018 (12) obj. -27.065
iterations 437</div>
<div>Cbc0038I Pass 13: suminf. 0.78011 (12) obj. -27.065
iterations 270</div>
<div>Cbc0038I Pass 14: suminf. 1.43020 (12) obj. -27.065
iterations 471</div>
<div>Cbc0038I Pass 15: suminf. 0.78011 (11) obj. -27.065
iterations 136</div>
<div>Cbc0038I Pass 16: suminf. 1.17016 (12) obj. -27.065
iterations 488</div>
<div>Cbc0038I Pass 17: suminf. 0.78011 (11) obj. -27.065
iterations 130</div>
<div>Cbc0038I Pass 18: suminf. 1.04014 (11) obj. -27.065
iterations 468</div>
<div>Cbc0038I Pass 19: suminf. 0.78011 (12) obj. -27.065
iterations 144</div>
<div>Cbc0038I Pass 20: suminf. 1.56022 (12) obj. -27.065
iterations 475</div>
<div>Cbc0038I Pass 21: suminf. 0.78011 (11) obj. -27.065
iterations 150</div>
<div>Cbc0038I Pass 22: suminf. 1.04014 (11) obj. -27.065
iterations 462</div>
<div>Cbc0038I Pass 23: suminf. 0.78011 (12) obj. -27.065
iterations 145</div>
<div>Cbc0038I Pass 24: suminf. 3.90054 (26) obj. -27.065
iterations 458</div>
<div>Cbc0038I Pass 25: suminf. 1.62522 (21) obj. -27.065
iterations 375</div>
<div>Cbc0038I Pass 26: suminf. 3.17016 (21) obj. -27.065
iterations 484</div>
<div>Cbc0038I Pass 27: suminf. 1.43020 (20) obj. -27.065
iterations 439</div>
<div>Cbc0038I Pass 28: suminf. 3.49521 (19) obj. -27.065
iterations 517</div>
<div>Cbc0038I Pass 29: suminf. 1.36519 (18) obj. -27.065
iterations 411</div>
<div>Cbc0038I Pass 30: suminf. 2.84512 (18) obj. -27.065
iterations 440</div>
<div>Cbc0038I Pass 31: suminf. 1.36519 (16) obj. -27.065
iterations 504</div>
<div>Cbc0038I No solution found this major pass</div>
<div>Cbc0038I Before mini branch and bound, 6498 integers at
bound fixed and 0 continuous</div>
<div>Cbc0038I Full problem 777 rows 6796 columns, reduced to 55
rows 170 columns</div>
<div>Cbc0038I Mini branch and bound did not improve solution
(841.72 seconds)</div>
<div>Cbc0038I After 841.72 seconds - Feasibility pump exiting
with objective of -27 - took 0.90 seconds</div>
</div>
<div><br>
</div>
<br>
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<br>
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