NAG FL Interface
e04ref (handle_​set_​linobj)

1 Purpose

e04ref is a part of the NAG optimization modelling suite and defines the linear objective function of the problem.

2 Specification

Fortran Interface
Subroutine e04ref ( handle, nvar, cvec, ifail)
Integer, Intent (In) :: nvar
Integer, Intent (Inout) :: ifail
Real (Kind=nag_wp), Intent (In) :: cvec(nvar)
Type (c_ptr), Intent (In) :: handle
C Header Interface
#include <nag.h>
void  e04ref_ (void **handle, const Integer *nvar, const double cvec[], Integer *ifail)
The routine may be called by the names e04ref or nagf_opt_handle_set_linobj.

3 Description

After the initialization routine e04raf has been called, e04ref may be used to define the objective function of the problem as a linear function cTx using a dense vector c unless the objective function has already been defined by another routine in the suite. This will typically be used for linear programming (LP)
minimize xn cTx   (a) subject to   lBBxuB,   (b) lxxux ,   (c) (1)
second-order cone programming (SOCP)
minimize xn cTx   (a) subject to lBBxuB,   (b) lxxux ,   (c) xGiKmi,i=1,,r,   (d) (2)
linear semidefinite programming problems (SDP)
minimize xn cTx   (a) subject to   i=1 n xi Aik - A0k 0 ,  k=1,,mA ,   (b) lBBxuB ,   (c) lxxux ,   (d) (3)
or SDP with bilinear matrix inequalities (BMI-SDP) where the objective function has only linear terms. It is recommended to use e04rff if the vector c is sparse. See Section 3.1 in the E04 Chapter Introduction for more details about the NAG optimization modelling suite.

4 References

None.

5 Arguments

1: handle Type (c_ptr) Input
On entry: the handle to the problem. It needs to be initialized by e04raf and must not be changed before the call to e04ref.
2: nvar Integer Input
On entry: n, the number of decision variables x in the problem. It must be unchanged from the value set during the initialization of the handle by e04raf.
3: cvecnvar Real (Kind=nag_wp) array Input
On entry: the dense vector c of the objective function.
4: ifail Integer Input/Output
On entry: ifail must be set to 0, -1 or 1 to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of 0 causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of -1 means that an error message is printed while a value of 1 means that it is not.
If halting is not appropriate, the value -1 or 1 is recommended. If message printing is undesirable, then the value 1 is recommended. Otherwise, the value -1 is recommended since useful values can be provided in some output arguments even when ifail0 on exit. When the value -1 or 1 is used it is essential to test the value of ifail on exit.
On exit: ifail=0 unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry ifail=0 or -1, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
ifail=1
The supplied handle does not define a valid handle to the data structure for the NAG optimization modelling suite. It has not been initialized by e04raf or it has been corrupted.
ifail=2
The problem cannot be modified in this phase any more, the solver has already been called.
ifail=3
The objective function has already been defined.
ifail=4
On entry, nvar=value, expected value=value.
Constraint: nvar must match the value given during initialization of handle.
ifail=-99
An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
ifail=-399
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.
ifail=-999
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

Not applicable.

8 Parallelism and Performance

e04ref is not threaded in any implementation.

9 Further Comments

None.

10 Example

See Section 10 in e04raf for links to all the examples in the suite.