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# holoscan::CPUThread

> CPU thread class.

CPU thread class.

A `CPUThread` resource can be added to an operator to control whether it will be pinned to a specific thread in a [ThreadPool](threadpool) (as used by [MultiThreadScheduler](multithreadscheduler)). See the [ThreadPool](threadpool) API documentation for a more detailed description of its usage.

[Application](application) authors should not need to use this class directly. It is used behind the scenes as needed by the [`holoscan::ThreadPool`](threadpool) class.

\==Parameters==

* **pin\_operator** (bool, optional): Whether or not an operator should be pinned to a specific thread (Default: false).
* **pin\_cores** (std::vector\<uint32\_t>, optional): CPU core IDs to pin the worker thread to. Empty vector means no core pinning (Default: empty).
* **sched\_policy** ([SchedulingPolicy](../typedefs/schedulingpolicy), optional): Linux real-time scheduling policy. kFirstInFirstOut is SCHED\_FIFO, kRoundRobin is SCHED\_RR, kDeadline is SCHED\_DEADLINE (Default: not set).
* **sched\_priority** (uint32\_t, optional): Thread priority for FirstInFirstOut and RoundRobin policies (Default: not set).
* **sched\_runtime** (uint64\_t, optional): Expected worst case execution time in nanoseconds for Deadline policy (Default: not set).
* **sched\_deadline** (uint64\_t, optional): Relative deadline in nanoseconds for Deadline policy (Default: not set).
* **sched\_period** (uint64\_t, optional): Period in nanoseconds for Deadline policy (Default: not set).

```cpp showLineNumbers={false}
#include <holoscan/cpu_thread.hpp>
```

**Inherits from:** `holoscan::gxf::GXFResource` (public)

---

## Constructors

### CPUThread \[#cputhread]

#### Move

```cpp showLineNumbers={false}
template <typename ArgT,
          typename... ArgsT,
          typename = std::enable_if_t<!std::is_base_of_v<::holoscan::Resource, std::decay_t<ArgT>> &&   (std::is_same_v<::holoscan::Arg, std::decay_t<ArgT>> ||   std::is_same_v<::holoscan::ArgList, std::decay_t<ArgT>>)>>
holoscan::CPUThread::CPUThread(
    ArgT &&arg,
    ArgsT &&... args
)
```

#### Overload 2

```cpp showLineNumbers={false}
holoscan::CPUThread::CPUThread(
    bool pin_operator = true
)
```

---

## Methods

### gxf\_typename \[#gxftypename]

```cpp showLineNumbers={false}
const char * holoscan::CPUThread::gxf_typename() const override
```

The underlying GXF component's name.

### setup \[#setup]

```cpp showLineNumbers={false}
void holoscan::CPUThread::setup(
    ComponentSpec &spec
) override
```

Define the resource specification.

**Parameters**

**`spec`** `ComponentSpec &`

The reference to the component specification.

---

### initialize \[#initialize]

```cpp showLineNumbers={false}
void holoscan::CPUThread::initialize() override
```

Initialize the component.

This method is called only once when the component is created for the first time, and use of light-weight initialization.

### pinned \[#pinned]

```cpp showLineNumbers={false}
bool holoscan::CPUThread::pinned() const
```

Returns whether the component is pinned to a worker thread.

### pin\_cores \[#pincores]

```cpp showLineNumbers={false}
std::vector<uint32_t> holoscan::CPUThread::pin_cores() const
```

CPU core IDs to pin the worker thread to (empty means no core pinning).

### sched\_policy \[#schedpolicy]

```cpp showLineNumbers={false}
holoscan::expected<SchedulingPolicy, holoscan::RuntimeError> holoscan::CPUThread::sched_policy() const
```

Real-time scheduling policy.

### sched\_priority \[#schedpriority]

```cpp showLineNumbers={false}
holoscan::expected<uint32_t, holoscan::RuntimeError> holoscan::CPUThread::sched_priority() const
```

Thread priority (only for FirstInFirstOut and RoundRobin policies).

### sched\_runtime \[#schedruntime]

```cpp showLineNumbers={false}
holoscan::expected<uint64_t, holoscan::RuntimeError> holoscan::CPUThread::sched_runtime() const
```

Expected worst case execution time in nanoseconds (only for Deadline policy).

### sched\_deadline \[#scheddeadline]

```cpp showLineNumbers={false}
holoscan::expected<uint64_t, holoscan::RuntimeError> holoscan::CPUThread::sched_deadline() const
```

Relative deadline in nanoseconds (only for Deadline policy).

### sched\_period \[#schedperiod]

```cpp showLineNumbers={false}
holoscan::expected<uint64_t, holoscan::RuntimeError> holoscan::CPUThread::sched_period() const
```

Period in nanoseconds (only for Deadline policy).

### is\_realtime \[#isrealtime]

```cpp showLineNumbers={false}
bool holoscan::CPUThread::is_realtime() const
```

Helper method to check if real-time scheduling is enabled.

### resource\_type \[#resourcetype]

```cpp showLineNumbers={false}
ResourceType holoscan::Resource::resource_type() const
```

Get the resource type.

**Returns:** The resource type.

### name \[#name]

#### Set the name of the resource (1)

```cpp showLineNumbers={false}
Resource & holoscan::Resource::name(
    const std::string &name
) &
```

Set the name of the resource.

**Returns:** The reference to the resource.

**Parameters**

**`name`** `const std::string &`

The name of the resource.

---

#### Set the name of the resource (2)

```cpp showLineNumbers={false}
Resource && holoscan::Resource::name(
    const std::string &name
) &&
```

Set the name of the resource.

**Returns:** The reference to the resource.

**Parameters**

**`name`** `const std::string &`

The name of the resource.

---

#### Const

const

```cpp showLineNumbers={false}
const std::string & holoscan::ComponentBase::name() const
```

Get the name of the component.

**Returns:** The name of the component.

### fragment \[#fragment]

#### Set the fragment of the resource

```cpp showLineNumbers={false}
Resource & holoscan::Resource::fragment(
    Fragment *fragment
)
```

Set the fragment of the resource.

**Returns:** The reference to the resource.

**Parameters**

**`fragment`** `Fragment *`

The pointer to the fragment of the resource.

---

#### Get a pointer to \[Fragment]\(fragment) object

```cpp showLineNumbers={false}
Fragment * holoscan::ComponentBase::fragment()
```

Get a pointer to [Fragment](fragment) object.

**Returns:** The Pointer to [Fragment](fragment) object.

#### Const

const

```cpp showLineNumbers={false}
const Fragment * holoscan::ComponentBase::fragment() const
```

Get a const pointer to [Fragment](fragment) object.

**Returns:** The const pointer to [Fragment](fragment) object.

### spec \[#spec]

#### Set the component specification to the resource

```cpp showLineNumbers={false}
Resource & holoscan::Resource::spec(
    const std::shared_ptr<ComponentSpec> &spec
)
```

Set the component specification to the resource.

**Returns:** The reference to the resource.

**Parameters**

**`spec`** `const std::shared_ptr<ComponentSpec> &`

The component specification.

---

#### Get the component specification of the resource

```cpp showLineNumbers={false}
ComponentSpec * holoscan::Resource::spec()
```

Get the component specification of the resource.

**Returns:** The pointer to the component specification.

### spec\_shared \[#specshared]

```cpp showLineNumbers={false}
std::shared_ptr<ComponentSpec> holoscan::Resource::spec_shared()
```

Get the shared pointer to the component spec.

**Returns:** The shared pointer to the component spec.

### id \[#id]

```cpp showLineNumbers={false}
int64_t holoscan::ComponentBase::id() const
```

Get the identifier of the component.

By default, the identifier is set to -1. It is set to a valid value when the component is initialized.

With the default executor (GXFExecutor), the identifier is set to the GXF component ID.

**Returns:** The identifier of the component.

### add\_arg \[#addarg]

#### Add an argument to the component (1)

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    const Arg &arg
)
```

Add an argument to the component.

**Parameters**

**`arg`** `const Arg &`

The argument to add.

---

#### Add an argument to the component (2)

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    Arg &&arg
)
```

Add an argument to the component.

**Parameters**

**`arg`** `Arg &&`

The argument to add.

---

#### Add a list of arguments to the component (1)

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    const ArgList &arg
)
```

Add a list of arguments to the component.

**Parameters**

**`arg`** `const ArgList &`

The list of arguments to add.

---

#### Add a list of arguments to the component (2)

```cpp showLineNumbers={false}
void holoscan::ComponentBase::add_arg(
    ArgList &&arg
)
```

Add a list of arguments to the component.

**Parameters**

**`arg`** `ArgList &&`

The list of arguments to add.

---

### args \[#args]

```cpp showLineNumbers={false}
std::vector<Arg> & holoscan::ComponentBase::args()
```

Get the list of arguments.

**Returns:** The vector of arguments.

### description \[#description]

```cpp showLineNumbers={false}
std::string holoscan::ComponentBase::description() const
```

Get a description of the component.

**Returns:** `YAML` string.

**See also:**
to\_yaml\_node()

### service \[#service]

```cpp showLineNumbers={false}
template <typename ServiceT = DefaultFragmentService>
std::shared_ptr<ServiceT> holoscan::ComponentBase::service(
    std::string_view id = ""
) const
```

Retrieve a registered fragment service or resource.

Retrieves a previously registered fragment service or resource by its type and optional identifier. Returns nullptr if no service/resource is found with the specified type and identifier.

Note that any changes to the service retrieval logic in this method should be synchronized with the implementation in `Fragment::service()` method to maintain consistency.

**Returns:** The shared pointer to the service/resource, or nullptr if not found or if type casting fails.

**Template parameters**

**`ServiceT`** `typename`

The type of the service/resource to retrieve. Must inherit from either [Resource](resource) or [FragmentService](fragmentservice). Defaults to [DefaultFragmentService](defaultfragmentservice) if not specified.

---

**Parameters**

**`id`** `std::string_view` — default: ""

The identifier of the service/resource. If empty, retrieves by type only.

---

### get\_service\_by\_type\_info \[#getservicebytypeinfo]

```cpp showLineNumbers={false}
std::shared_ptr<FragmentService> holoscan::ComponentBase::get_service_by_type_info(
    const std::type_info &service_type,
    std::string_view id = ""
) const
```

Retrieve a registered fragment service or resource for Python bindings.

This is a helper method for Python bindings to retrieve a service by its C++ type info.

**Returns:** The shared pointer to the base service, or nullptr if not found.

**Parameters**

**`service_type`** `const std::type_info &`

The type info of the service/resource to retrieve.

---

**`id`** `std::string_view` — default: ""

The identifier of the service/resource. If empty, retrieves by type only.

---

### gxf\_context \[#gxfcontext]

#### Mutable

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_context(
    gxf_context_t gxf_context
)
```

#### Const

const

```cpp showLineNumbers={false}
gxf_context_t holoscan::gxf::GXFComponent::gxf_context() const
```

### gxf\_eid \[#gxfeid]

#### Mutable

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_eid(
    gxf_uid_t gxf_eid
)
```

#### Const

const

```cpp showLineNumbers={false}
gxf_uid_t holoscan::gxf::GXFComponent::gxf_eid() const
```

### gxf\_tid \[#gxftid]

#### Mutable

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_tid(
    gxf_tid_t gxf_tid
)
```

#### Const

const

```cpp showLineNumbers={false}
gxf_tid_t holoscan::gxf::GXFComponent::gxf_tid() const
```

### gxf\_cid \[#gxfcid]

#### Mutable

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_cid(
    gxf_uid_t gxf_cid
)
```

#### Const

const

```cpp showLineNumbers={false}
gxf_uid_t holoscan::gxf::GXFComponent::gxf_cid() const
```

### gxf\_cname \[#gxfcname]

#### Overload 1

```cpp showLineNumbers={false}
std::string & holoscan::gxf::GXFComponent::gxf_cname()
```

#### Overload 2

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_cname(
    const std::string &name
)
```

### gxf\_graph\_entity \[#gxfgraphentity]

#### Overload 1

```cpp showLineNumbers={false}
std::shared_ptr<nvidia::gxf::GraphEntity> holoscan::gxf::GXFComponent::gxf_graph_entity()
```

#### Overload 2

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_graph_entity(
    std::shared_ptr<nvidia::gxf::GraphEntity> graph_entity
)
```

### gxf\_entity\_group\_name \[#gxfentitygroupname]

```cpp showLineNumbers={false}
std::string holoscan::gxf::GXFComponent::gxf_entity_group_name()
```

The name of the entity group this component belongs to.

### gxf\_entity\_group\_id \[#gxfentitygroupid]

```cpp showLineNumbers={false}
gxf_uid_t holoscan::gxf::GXFComponent::gxf_entity_group_id()
```

The group id of the entity group this component belongs to.

### gxf\_cptr \[#gxfcptr]

```cpp showLineNumbers={false}
void * holoscan::gxf::GXFComponent::gxf_cptr()
```

### gxf\_component \[#gxfcomponent]

```cpp showLineNumbers={false}
nvidia::gxf::Handle<nvidia::gxf::Component> holoscan::gxf::GXFComponent::gxf_component()
```

### gxf\_initialize \[#gxfinitialize]

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::gxf_initialize()
```

### set\_gxf\_parameter \[#setgxfparameter]

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::set_gxf_parameter(
    const std::string &component_name,
    const std::string &key,
    ParameterWrapper &param_wrap
)
```

Set a given parameter on the underlying GXF component.

### reset\_gxf\_graph\_entity \[#resetgxfgraphentity]

```cpp showLineNumbers={false}
void holoscan::gxf::GXFComponent::reset_gxf_graph_entity()
```

### add\_to\_graph\_entity \[#addtographentity]

#### Overload 1

virtual

```cpp showLineNumbers={false}
virtual void holoscan::CPUThread::add_to_graph_entity(
    Operator *op
)
```

#### Overload 2

```cpp showLineNumbers={false}
void holoscan::CPUThread::add_to_graph_entity(
    Fragment *fragment,
    const std::shared_ptr<nvidia::gxf::GraphEntity> &graph_entity
)
```

### to\_yaml\_node \[#toyamlnode]

```cpp showLineNumbers={false}
YAML::Node holoscan::CPUThread::to_yaml_node() const override
```

Get a `YAML` representation of the resource.

**Returns:** `YAML` node including type and specs of the resource in addition to the base component properties.

### set\_parameters \[#setparameters]

```cpp showLineNumbers={false}
void holoscan::CPUThread::set_parameters() override
```

This method is invoked by `GXFResource::initialize()`.

By overriding this method, we can modify how GXF Codelet's parameters are set from the arguments.

### handle\_dev\_id \[#handledevid]

```cpp showLineNumbers={false}
bool holoscan::CPUThread::handle_dev_id(
    std::optional<int32_t> &dev_id_value
)
```

### reset\_backend\_objects \[#resetbackendobjects]

```cpp showLineNumbers={false}
void holoscan::CPUThread::reset_backend_objects() override
```

Reset any backend-specific state.

### update\_params\_from\_args \[#updateparamsfromargs]

#### Update parameters based on the specified arguments

```cpp showLineNumbers={false}
void holoscan::Resource::update_params_from_args()
```

Update parameters based on the specified arguments.

#### Update parameters based on the specified arguments (with params)

```cpp showLineNumbers={false}
void holoscan::ComponentBase::update_params_from_args(
    std::unordered_map<std::string, ParameterWrapper> &params
)
```

Update parameters based on the specified arguments.

### service\_provider \[#serviceprovider]

```cpp showLineNumbers={false}
void holoscan::ComponentBase::service_provider(
    FragmentServiceProvider *provider
)
```

Set the service provider that owns this component.

---

## Static methods

### register\_converter \[#registerconverter]

```cpp showLineNumbers={false}
template <typename typeT>
static void holoscan::ComponentBase::register_converter()
```

Register the argument setter for the given type.

If an operator or resource has an argument with a custom type, the argument setter must be registered using this method.

The argument setter is used to set the value of the argument from the `YAML` configuration.

This method can be called in the initialization phase of the operator/resource (e.g., `initialize()`). The example below shows how to register the argument setter for the custom type (`Vec3`):

It is assumed that `YAML::convert<T>::encode` and `YAML::convert<T>::decode` are implemented for the given type. You need to specialize the `YAML::convert<>` template class.

For example, suppose that you had a `Vec3` class with the following members:

You can define the `YAML::convert<Vec3>` as follows in a '.cpp' file:

Please refer to the [yaml-cpp documentation](https://github.com/jbeder/yaml-cpp/wiki/Tutorial#converting-tofrom-native-data-types) for more details.

**Template parameters**

**`typeT`** `typename`

The type of the argument to register.

---

**Example**

```cpp showLineNumbers={false}
void MyOp::initialize() {
  register_converter<Vec3>();
}
```

**Example**

```cpp showLineNumbers={false}
struct Vec3 {
  // make sure you have overloaded operator==() for the comparison
  double x, y, z;
};
```

**Example**

```cpp showLineNumbers={false}
namespace YAML {
template<>
struct convert<Vec3> {
  static Node encode(const Vec3& rhs) {
    Node node;
    node.push_back(rhs.x);
    node.push_back(rhs.y);
    node.push_back(rhs.z);
    return node;
  }

  static bool decode(const Node& node, Vec3& rhs) {
    if(!node.IsSequence() || node.size() != 3) {
      return false;
    }

    rhs.x = node[0].as<double>();
    rhs.y = node[1].as<double>();
    rhs.z = node[2].as<double>();
    return true;
  }
};
}
```

### register\_argument\_setter \[#registerargumentsetter]

```cpp showLineNumbers={false}
template <typename typeT>
void holoscan::ComponentBase::register_argument_setter()
```

Register the argument setter for the given type.

Please refer to the documentation of `register_converter()` for more details.

**Template parameters**

**`typeT`** `typename`

The type of the argument to register.

---

---

## Types

### ResourceType

[Resource](resource) type used for the initialization of the resource.

| Name      | Value | Description      |
| --------- | ----- | ---------------- |
| `kNative` |       | Native resource. |
| `kGXF`    |       | GXF resource.    |

---

## Member variables

| Name                | Type                                            | Description                                                                |
| ------------------- | ----------------------------------------------- | -------------------------------------------------------------------------- |
| `pin_operator_`     | `Parameter< bool >`                             | Whether or not to pin an operator to a specific thread.                    |
| `pin_cores_`        | `Parameter< std::vector< uint32_t > >`          | CPU core IDs to pin the worker thread to.                                  |
| `sched_policy_`     | `Parameter< YAML::Node >`                       | Real-time scheduling policy.                                               |
| `sched_priority_`   | `Parameter< uint32_t >`                         | Thread priority.                                                           |
| `sched_runtime_`    | `Parameter< uint64_t >`                         | Expected worst case execution time in nanoseconds.                         |
| `sched_deadline_`   | `Parameter< uint64_t >`                         | Relative deadline in nanoseconds.                                          |
| `sched_period_`     | `Parameter< uint64_t >`                         | Period in nanoseconds.                                                     |
| `gxf_typename_`     | `std::string`                                   | The GXF type name (used for [GXFComponentResource](gxfcomponentresource)). |
| `resource_type_`    | `ResourceType`                                  | The type of the resource.                                                  |
| `is_initialized_`   | `bool`                                          | Whether the resource is initialized.                                       |
| `spec_`             | `std::shared_ptr< ComponentSpec >`              | The component specification.                                               |
| `id_`               | `int64_t`                                       | The ID of the component.                                                   |
| `name_`             | `std::string`                                   | Name of the component.                                                     |
| `fragment_`         | `Fragment *`                                    | Pointer to the fragment that owns this component.                          |
| `args_`             | `std::vector< Arg >`                            | List of arguments.                                                         |
| `service_provider_` | `FragmentServiceProvider *`                     | Pointer to the service provider.                                           |
| `gxf_context_`      | `gxf_context_t`                                 |                                                                            |
| `gxf_eid_`          | `gxf_uid_t`                                     |                                                                            |
| `gxf_tid_`          | `gxf_tid_t`                                     |                                                                            |
| `gxf_cid_`          | `gxf_uid_t`                                     |                                                                            |
| `gxf_graph_entity_` | `std::shared_ptr< nvidia::gxf::GraphEntity >`   |                                                                            |
| `gxf_cname_`        | `std::string`                                   |                                                                            |
| `gxf_component_`    | `nvidia::gxf::Handle< nvidia::gxf::Component >` |                                                                            |
| `gxf_cptr_`         | `void *`                                        |                                                                            |