# Controls System

The control system in MOOSE has one primary purpose: to modify input parameters during runtime of a MOOSE-based simulation.

## Creating a Controllable Parameter

The input parameters of objects you which to be controlled must:

• Store parameter as a const reference; in your *.h files, declare storage for the parameters as follows.

  const Real & _value;

(framework/include/bcs/DirichletBC.h)

• Initialize the reference in the *.C file as follows.

  : NodalBC(parameters), _value(getParam<Real>("value"))

(framework/src/bcs/DirichletBC.C)

In order to "control" a parameter it must be communicated that the parameter is allowed to be controlled, this is done in the validParams function as in Listing 1. The input can be a single value or a space separated list of parameters.

Listing 1: Example validParams method that declares a parameter as controllable.

template <>
InputParameters
validParams<DirichletBC>()
{
InputParameters p = validParams<NodalBC>();
p.declareControllable("value");
p.addClassDescription("Imposes the essential boundary condition $u=g$, where $g$ "
"is a constant, controllable value.");
return p;
}

(framework/src/bcs/DirichletBC.C)
note

The declareControllable method also accepts a space separated list of parameters.

## Create a Control object

Control objects are similar to other systems in MOOSE. You create a control in your application by inheriting from the Control C++ class in MOOSE. It is required to override the execute method in your custom object. Within this method the following methods are generally used to get or set controllable parameters:

• getControllableValue <br> This method returns the current controllable parameter, in the case that multiple parameters are being controlled, only the first value will be returned and a warning will be produced if the values are differ (this warning may be disabled).

• setControllableValue <br> This method allows for a controllable parameter to be changed, in the case that multiple parameters are being controlled, all of the values will be set.

These methods operator in a similar fashion as other systems in MOOSE (e.g., getPostprocessorValue in the Postprocessors system), each expects an input parameter name (std::string) that is prescribed in the validParams method.

There are additional overloaded methods that allow for the setting and getting of controllable values with various inputs for prescribing the parameter name, but the the two listed above are generally what is needed. Please refer to the source code for a complete list.

## Controls Block

Control objects are defined in the input file in the Controls block, similar to other systems in MOOSE. For example, the following input file snippet shows the use of the RealFunctionControl object.

Listing 2: Example of a Control object used in a MOOSE input file.

[Controls]
[./func_control]
type = RealFunctionControl
parameter = '*/*/coef'
function = 'func_coef'
execute_on = 'initial timestep_begin'
[../]
[]

(test/tests/controls/real_function_control/real_function_control.i)

## Object and Parameter Names

Notice that in Listing 2 the syntax for specifying a parameter is shown. In general, the syntax for a parameter name is specified as: block/object/name.

• block: specifies the input file block name (e.g., "Kernels", "BCs").

• object: specifies the input file sub-block name (e.g., "diff" in Listing 3).

• name: specifies the parameter name (e.g., "coef" in Listing 3).

Listing 3: Example of a "Kernel" block that contains a parameter that is controlled via a MOOSE Control object.

[Kernels]
[./diff]
type = CoefDiffusion
variable = u
coef = 0.1
[../]
[./time]
type = TimeDerivative
variable = u
[../]
[]

(test/tests/controls/real_function_control/real_function_control.i)

As shown in Listing 2 an asterisk ("*") can be substituted for any one of these three "names", doing so allows multiple parameters to match and be controlled simultaneously.

In similar fashion, object names can be defined (e.g., as in the TimePeriod) object. In this case, the general name scheme is the same as above but the parameter name is not included.

In both cases there is an alternative form for defining an object and parameter names: base::object/name. In this case "base" is the MOOSE base system that the object is derived from. For example, Kernel::diff/coef.

## Available Objects

• Moose App
• RealFunctionControlSets the value of a 'Real' input parameters to the value of a provided function.
• TimePeriodControl the enabled/disabled state of objects with time.
• Stochastic Tools App
• MultiAppCommandLineControlControl for modifying the command line arguments of MultiApps.
• SamplerReceiverControl for receiving data from a Sampler via SamplerTransfer.