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Dear Ahmad, <br>
<br>
as you noticed yourself, you can only access the actual reduced
costs (corresponding to the solved LP at the current focus node)
during the solving stage. When creating a heuristic, you can set the
right timing mask such that it is only called when an LP was solved
at a node, using the timing <a moz-do-not-send="true"
href="http://scip.zib.de/doc/html/type__timing_8h.php#ac4cb022a363958364724303ce7a76897">SCIP_HEURTIMING_AFTERLPNODE.</a><br>
<br>
In addition, you must ensure yourself that the LP was solved to
optimality for correct reduced costs by testing SCIPgetLPSolStat()
against SCIP_LPSOLSTAT_OPTIMAL.<br>
<br>
FYI: You can also access information about the best reduced costs
(for root reduced cost propagation) that SCIP found during the root
LP processing using the methods SCIPvarGetBestRootRedcost,
SCIPvarGetBestRootSol, and SCIPvarGetBestRootLPObjval.<br>
<br>
Let me know if this helps you continue, or if you need further
advice on this.<br>
<br>
Have a nice weekend<br>
Gregor<br>
<br>
<br>
<div class="moz-cite-prefix">Am 06.09.2017 um 10:27 schrieb Ahmad
Moradi:<br>
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<div>Dear SCIP community,<br>
<br>
</div>
I am implementing a heuristic algorithm who seeks to find
a good (primal) solution of a given MILP. The algorithm
actually starts by looking at reduced-cost value of
variables after solving LP relaxation of the MILP.<br>
<br>
</div>
I simply coded the LP and solved it. Then I used the method
<span style="font-family:monospace,monospace">SCIPgetVarRedcost()</span>
to see reduced-cost value of my original LP variables.
However, I noticed that some of the values are negative,
contradicting to optimality as the LP has minimization
objective sense. Then I found that scip is not in the
solving stage (SCIP_STAGE_SOLVING) as required by <span
style="font-family:monospace,monospace">SCIPgetVarRedcost()</span>...
is that the why some reduced-costs get negative? if so, how
can I access correct reduced cost values (according to
optimal basis).<br>
<br>
</div>
Bests,<br>
</div>
Ahmad<br>
</div>
<br>
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