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This is an advanced routine. Advanced routines typically demand a profound understanding of the algorithms used by ILOG CPLEX. Thus they incur a higher risk of incorrect behavior in your application, behavior that can be difficult to debug. Therefore, ILOG encourages you to consider carefully whether you can accomplish the same task by means of other Callable Library routines instead.
The routine CPXprechgobj is used to change the objective
function coefficients of an LP problem object and its associated presolved
LP problem object. Note that the CPLEX parameter
CPX_PARAM_REDUCE must be set to CPX_PREREDUCE_PRIMALONLY
(1) or CPX_PREREDUCE_NOPRIMALORDUAL (0) at the time of
the presolve in order to change objective coefficients and preserve the
presolved problem. This routine should be used in place of
CPXchgobj when it is desired to preserve the presolved
problem.
The arguments and operation of CPXprechgobj are the same
as those of CPXchgobj. The objective coefficient changes are
applied to both the original LP problem object and the associated presolved
LP problem object.
Example
status = CPXprechgobj (env, lp, objcnt, objind, objval);
See also the example adpreex1.c in the standard
distribution.