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<div class="moz-cite-prefix">Marco,<br>
<br>
Just switch Gomory i.e. -gomory off -gmi ifmove <br>
<br>
Will be just the same as next release. You may wish to make it
-gmi root.<br>
<br>
John Forrest<br>
<br>
<br>
On 24/03/15 11:18, mg wrote:<br>
</div>
<blockquote
cite="mid:CAOayR=b+Z7ZQtxCR91_twpp+qRQNk_VieCcB4Mqd25Zg1fkZTQ@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>John, thanks a lot for the fast reply :)</div>
<div><br>
</div>
<div>
<div>Do you think I can still use the 2.9.3 version (release)
and just turn gomory cuts off ?</div>
<div>Does this version (2.9.3) suffer of other known problems
that may be worth switching to svn stable ?<br>
</div>
<div>(I usually prefer to update to new release versions when
possible...) <br>
</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Marco</div>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2015-03-24 11:08 GMT+01:00 John Forrest
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:john.forrest@fastercoin.com" target="_blank">john.forrest@fastercoin.com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
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<div>Marco,<br>
<br>
Thanks. I wish I knew why Gomory cuts have started
giving trouble.<br>
<br>
If I run with debug I get<br>
<br>
Cut with 7 coefficients, cuts off known solutions by
1.403e-05, lo=-1.79769e+308, ub=9.75001<br>
( 3 , -9.75 ) ( 4 , -9.75 ) ( 6 , 9.75001 ) ( 7 ,
9.75001 ) ( 8 , 9.75001 ) ( 9 , 9.75001 ) ( 10 , 9.75001
) <br>
Non zero solution values are<br>
( 3 , 1 ) ( 4 , 1 ) ( 7 , 1 ) ( 9 , 1 ) ( 10 , 1 ) <br>
<br>
so you can see it is an accuracy problem.<br>
<br>
Yesterday I had changed stable so that CglGomory cuts
were not default, but CglGMI was default - as CglGMI is
more stable. I then decided that was a bit drastic so
changed it back unless a Cbc configure option is set.<br>
<br>
So in stable (svn) you now have several options.<br>
<br>
In configure use -DSWAP_GOMORY to use CglGMI as default
(you can still switch back by using gomory ifmove etc.).<br>
<br>
In configure use -DWEAKEN_CUTS=1. This weakens cuts a
bit if they look slightly odd.<br>
<br>
If performance does not suffer, I would suggest first
option - or just change to using -gomory off -gmi
ifmove.<br>
<br>
John Forrest
<div>
<div class="h5"><br>
<br>
On 24/03/15 08:23, mg wrote:<br>
</div>
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<div>
<div class="h5">
<div dir="ltr">Hi All,
<div>I'm currently solving some very small
multiknapsack-like problems and I got an
infeasibility on the attached problem (CBC
version release 2.9.3)</div>
<div><br>
</div>
<div>It seems related to some wrong cut, since
disabling the cut generators (with cutsonoff
off) it works.</div>
<div><br>
</div>
<div>I don't know if it's important, but if you
look at the attached LP, you can see a
constraint called "PrimaryObjAsConstr" that
comes from a previous solve where this
constraint was actually the objective function. </div>
<div>Well, the RHS of this contraint is the
objective value of the previous solve (4) plus a
tolerance (0.1). If I put it to 4, the model is
solved without any problem even with the cut
generators enabled. Does this lead to some
integer-related stuff ?</div>
<div><br>
</div>
<div>For the moment I can solve it by disabling
the cut generation, but I wanted to report the
issue that might rise again in other cases.</div>
<div><br>
</div>
<div>Thanks in advance,</div>
<div>Marco</div>
</div>
<br>
<fieldset></fieldset>
<br>
</div>
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