# NAG CPP Interfacenagcpp::opt::handle_set_linobj (e04re)

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## 1Purpose

handle_set_linobj is a part of the NAG optimization modelling suite and defines or redefines the objective function of the problem to be linear.

## 2Specification

```#include "e04/nagcpp_e04re.hpp"
#include "e04/nagcpp_class_CommE04RA.hpp"
```
```template <typename COMM, typename CVEC>

void function handle_set_linobj(COMM &comm, const CVEC &cvec, OptionalE04RE opt)```
```template <typename COMM, typename CVEC>

void function handle_set_linobj(COMM &comm, const CVEC &cvec)```

## 3Description

After the handle has been initialized (e.g., handle_​init has been called), handle_set_linobj may be used to define the objective function of the problem as a linear function ${c}^{\mathrm{T}}x$ using a dense vector $c$. If the objective function has already been defined, it will be overwritten. If $c=0$, any existing objective function is removed, no new one is added and the problem will be solved as a feasible point problem. It is recommended to use handle_​set_​quadobj if the vector $c$ is sparse. e04tef (no CPP interface) may be used to set individual elements ${c}_{i}$ of the linear objective.
This will typically be used for Linear Programming (LP)
 $minimize x∈ℝn cTx (a) subject to lB≤Bx≤uB, (b) lx≤x≤ux , (c)$ (1)
Second-order Cone Programming (SOCP)
 $minimize x∈ℝn cTx (a) subject to lB≤Bx≤uB, (b) lx≤x≤ux , (c) xGi∈Kmi,i=1,…,r, (d)$ (2)
linear Semidefinite Programming problems (SDP)
 $minimize x∈ℝn cTx (a) subject to ∑ i=1 n xi Aik - A0k ⪰ 0 , k=1,…,mA , (b) lB≤Bx≤uB , (c) lx≤x≤ux , (d)$ (3)
or SDP with bilinear matrix inequalities (BMI-SDP) where the objective function has only linear terms. See Section 3.1 in the E04 Chapter Introduction for more details about the NAG optimization modelling suite.

None.

## 5Arguments

1: $\mathbf{comm}$CommE04RA Input/Output
Communication structure. An object of either the derived class CommE04RA or its base class NoneCopyableComm can be supplied. It is recommended that the derived class is used. If the base class is supplied it must first be initialized via a call to opt::handle_init (e04ra).
2: $\mathbf{cvec}\left({\mathbf{nvar}}\right)$double array Input
On entry: the dense vector $c$ of the objective function.
3: $\mathbf{opt}$OptionalE04RE Input/Output
Optional parameter container, derived from Optional.

1: $\mathbf{nvar}$
$n$, the current number of decision variables $x$ in the model.

## 6Exceptions and Warnings

Errors or warnings detected by the function:
All errors and warnings have an associated numeric error code field, errorid, stored either as a member of the thrown exception object (see errorid), or as a member of opt.ifail, depending on how errors and warnings are being handled (see Error Handling for more details).
Raises: ErrorException
$\mathbf{errorid}=1$
comm::handle has not been initialized.
$\mathbf{errorid}=1$
comm::handle does not belong to the NAG optimization modelling suite,
has not been initialized properly or is corrupted.
$\mathbf{errorid}=1$
comm::handle has not been initialized properly or is corrupted.
$\mathbf{errorid}=2$
The problem cannot be modified right now, the solver is running.
$\mathbf{errorid}=4$
On entry, ${\mathbf{nvar}}=⟨\mathit{value}⟩$,
expected $\mathrm{value}=⟨\mathit{value}⟩$.
Constraint: ${\mathbf{nvar}}$ must match the current number of variables
of the model in the comm::handle.
$\mathbf{errorid}=10601$
On entry, argument $⟨\mathit{\text{value}}⟩$ must be a vector of size $⟨\mathit{\text{value}}⟩$ array.
Supplied argument has $⟨\mathit{\text{value}}⟩$ dimensions.
$\mathbf{errorid}=10601$
On entry, argument $⟨\mathit{\text{value}}⟩$ must be a vector of size $⟨\mathit{\text{value}}⟩$ array.
Supplied argument was a vector of size $⟨\mathit{\text{value}}⟩$.
$\mathbf{errorid}=10601$
On entry, argument $⟨\mathit{\text{value}}⟩$ must be a vector of size $⟨\mathit{\text{value}}⟩$ array.
The size for the supplied array could not be ascertained.
$\mathbf{errorid}=10602$
On entry, the raw data component of $⟨\mathit{\text{value}}⟩$ is null.
$\mathbf{errorid}=10603$
On entry, unable to ascertain a value for $⟨\mathit{\text{value}}⟩$.
$\mathbf{errorid}=10605$
On entry, the communication class $⟨\mathit{\text{value}}⟩$ has not been initialized correctly.
$\mathbf{errorid}=-99$
An unexpected error has been triggered by this routine.
$\mathbf{errorid}=-399$
Your licence key may have expired or may not have been installed correctly.
$\mathbf{errorid}=-999$
Dynamic memory allocation failed.

Not applicable.

## 8Parallelism and Performance

Please see the description for the underlying computational routine in this section of the FL Interface documentation.