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Hi Matheus,<br>
<br>
your reasoning about negation is correct, so I would expect that the
LP solution satisfies ** at CONSENFOLP. A special case occurs if the
knapsack constraint is flagged by (not initial/not separate/not
check), in which case the constraint is not immediately part of the
root LP and might not be separated at violation. <br>
<br>
Note that the knapsack constraint handler has a very low enforcement
priority, -600000. Probably, the enforcement priority of your
constraint handler is higher, and the knapsack constraint handler
would add its constraint to the LP in the same enforcement round,
but later?<br>
<br>
Kind regards,<br>
Gregor<br>
<br>
<div class="moz-cite-prefix">Am 06.12.19 um 01:01 schrieb Matheus
Ota:<br>
</div>
<blockquote type="cite"
cite="mid:CAL0UnZ2WSfGm2R5JvD1bqEcsENLcmbP=QwUZ+6SmG+-fGwRQ2g@mail.gmail.com">
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<div>Hi all,</div>
<div><br>
</div>
<div>First I would like to say that I'm very grateful for all
the help I received from this mailing list! I have a question
regarding a MIP model that I'm solving. I have some equalities
of the following type</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>x_i,0 + x_i,1 == 1, for i = 0, ..., 8 (*)<br>
</div>
</blockquote>
<div><br>
</div>
<div> Thus, SCIP presolve routines replace some of my variables
(x_i,0) by the negation of other variables (1 - x_i,1). In the
transformed model I have only this constraint</div>
<div>
<p style="margin:0px;text-indent:0px;white-space:pre-wrap"><span style="color:rgb(0,0,0)">
</span></p>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<p style="margin:0px;text-indent:0px;white-space:pre-wrap"><span style="color:rgb(0,0,0)">[knapsack] <R>: +1<~t_x_8,1>[B] +1<~t_x_7,1>[B] +1<~t_x_6,1>[B] +1<~t_x_5,1>[B] +1<~t_x_4,1>[B] +1<~t_x_3,1>[B] +1<~t_x_2,1>[B] +1<~t_x_1,1>[B] +1<~t_x_0,1>[B] <= 4;</span></p>
</blockquote>
<div><br>
</div>
<div> And each variable x is binary. The tilde (~) means
negation here? If so, replacing <~t_x_i,1> by
<t_x_i,0> this would give</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div><t_x_8,0> + ... + <t_x_0,0><= 4 (**)<br>
</div>
</blockquote>
<div><br>
</div>
<div>But at the CONSENFOLP method, SCIP is entering with a
"solution" S with x_i,0 = 1 and x_i,1 = 0, for i = 0, ...,
8. Which is infeasible because violates (**). But the SCIP
documentation says that CONSENFOLP is called when an LP
solution is available. But this solution S do not respect
the constraints in my LP. I'm a little confused with this
behavior and would be glad if someone could give me some
light here.</div>
<div><br>
</div>
<div>Thanks!</div>
<div>Matheus<br>
</div>
</div>
</div>
<br>
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</blockquote>
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