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<div class="moz-cite-prefix">Dear Diego,<br>
<br>
</div>
<blockquote cite="mid:a6d9118385a6c42a300a8af99a593783@us.es"
type="cite">I have implemented a branch-and-price-procedure with a
pricer which seems working in the PRICERREDCOST. But in the
instances that it need to use PRICERFARKAS I am obtaining some
farkas multipliers with strange values, like -e99. Indeed this
dual variable should be nonnegative.</blockquote>
this sounds strange. Can you please check with SCIPgetLPSolstat()
that the LP is really infeasible and with SCIProwIsInLP() that the
row corresponding to the constraint for which you get the dual
farkas multiplier is contained in the LP (you can get the row of a
linear constraint with SCIPgetRowLinear()). Did you mark the
constraint to be modifiable?<br>
<br>
<blockquote cite="mid:a6d9118385a6c42a300a8af99a593783@us.es"
type="cite">
<p>Because of this problem, I would like to know if SCIP by itself
is able to close an infeasible node since the variables fixed
avoid any feasible solution <strong>and how</strong>.</p>
</blockquote>
Yes, SCIP can detect the infeasibility of a node in the domain
propagation step. For example, if you have a constraint x + y = 1
and x and y were both fixed to 0, SCIP will detect the infeasibility
and cut off the node. However, this is only done if the constraint
was not marked to be modifiable, since otherwise pricing might add
more variables to the constraint and there might still be feasible
solutions with x = y = 0.<br>
<br>
<blockquote cite="mid:a6d9118385a6c42a300a8af99a593783@us.es"
type="cite">
<p>My Farkas pricing is similar to the Reduced cost pricing whith
0 in the coefficients of the objective function
and SCIPgetDualfarkasLinear() instead of SCIPgetDualsolLinear().</p>
</blockquote>
This is how it should be.<br>
<br>
Best,<br>
Gerald<br>
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