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XPRBgetdual

Purpose

Get dual value.

Synopsis

double XPRBgetdual(XPRBctr ctr);  

Argument

ctr	Reference to a constraint.

Return value

Dual value for the constraint, 0 in case of an error.

Example

XPRBprob expl2;
XPRBctr ctr2;
XPRBarrvar ty1;
double dval;
   ...
expl2 = XPRBnewprob("example2");
ty1 = XPRBnewarrvar(expl2, 5, XPRB_PL, "arry1", 0, 500);
ctr2 = XPRBnewsum(expl2, "r2", ty1, XPRB_E, 9);
XPRBsolve(expl2, "l");
dval = XPRBgetdual(ctr2);

This obtains the dual value for the constraint ctr2.

Further information

This function returns the dual value for a constraint. The user may wish to test first whether this constraint is part of the problem, for instance by checking that the row number is non-negative.
If this function is called after completion of a global search and an integer solution has been found (that is, if function XPRBgetmipstat returns values XPRB_MIP_SOLUTION or XPRB_MIP_OPTIMAL), it returns the value in the best integer solution. If no integer solution is available after a global search this function outputs a warning and returns 0. In all other cases it returns the dual value in the last LP that has been solved. If this function is used during the execution of an optimization process (for instance in Optimizer library callback functions) it needs to be preceded by a call to XPRBsync with the flag XPRB_XPRS_SOL.