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# holoscan::MultiThreadScheduler

> Multi-Thread scheduler.

Multi-Thread scheduler.

This is a multi-thread scheduler that uses an event-based design. In addition to the specified [`worker_thread_number`](#workerthreadnumber) of threads for executing operators, it utilizes an additional polling thread that is used to check the execution readiness status of operators at period specified by [`check_recession_period_ms`](#checkrecessionperiodms).

\==Parameters==

* **worker\_thread\_number** (int64\_t): The number of (CPU) worker threads to use for executing operators. Defaults to 1.
* **stop\_on\_deadlock** (bool): If True, the application will terminate if a deadlock state is reached. Defaults to true.
* **stop\_on\_deadlock\_timeout** (int64\_t): The amount of time (in ms) before an application is considered to be in deadlock. Defaults to 0.
* **check\_recession\_period\_ms** (int64\_t): How often the polling thread checks for whether an operator is ready to execute. The value is in ms (default: 5).
* **max\_duration\_ms\_** (int64\_t, optional): Terminate the application after the specified duration even if deadlock does not occur. If unspecified, the application can run indefinitely.

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

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

***

## Constructors

### MultiThreadScheduler \[#multithreadscheduler]

#### Move

inline

explicit

```cpp showLineNumbers={false}
template <typename ArgT,
          typename... ArgsT,
          typename = std::enable_if_t<!std::is_base_of_v<::holoscan::Scheduler, 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::MultiThreadScheduler::MultiThreadScheduler(
    ArgT &&arg,
    ArgsT &&... args
)
```

#### Default

```cpp showLineNumbers={false}
holoscan::MultiThreadScheduler::MultiThreadScheduler() = default
```

***

## Methods

### gxf\_typename \[#gxftypename]

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

Get the type name of the GXF scheduler.

The returned string is the type name of the GXF scheduler and is used to create the GXF scheduler.

Example: "nvidia::holoscan::GreedyScheduler"

**Returns:** The type name of the GXF scheduler.

### clock \[#clock]

```cpp showLineNumbers={false}
std::shared_ptr<Clock> holoscan::MultiThreadScheduler::clock() override
```

Get the [Clock](clock) used by the scheduler.

**Returns:** The [Clock](clock) used by the scheduler.

### setup \[#setup]

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

Define the scheduler specification.

**Parameters**

The reference to the component specification.

### initialize \[#initialize]

```cpp showLineNumbers={false}
void holoscan::MultiThreadScheduler::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.

### worker\_thread\_number \[#workerthreadnumber]

```cpp showLineNumbers={false}
int64_t holoscan::MultiThreadScheduler::worker_thread_number() const
```

### stop\_on\_deadlock \[#stopondeadlock]

```cpp showLineNumbers={false}
bool holoscan::MultiThreadScheduler::stop_on_deadlock() const
```

### check\_recession\_period\_ms \[#checkrecessionperiodms]

```cpp showLineNumbers={false}
int64_t holoscan::MultiThreadScheduler::check_recession_period_ms() const
```

### stop\_on\_deadlock\_timeout \[#stopondeadlocktimeout]

```cpp showLineNumbers={false}
int64_t holoscan::MultiThreadScheduler::stop_on_deadlock_timeout() const
```

### network\_connection\_timeout \[#networkconnectiontimeout]

```cpp showLineNumbers={false}
int64_t holoscan::MultiThreadScheduler::network_connection_timeout() const
```

### max\_duration\_ms \[#maxdurationms]

```cpp showLineNumbers={false}
int64_t holoscan::MultiThreadScheduler::max_duration_ms() const
```

### get \[#get]

```cpp showLineNumbers={false}
nvidia::gxf::MultiThreadScheduler * holoscan::MultiThreadScheduler::get() const
```

### gxf\_clock \[#gxfclock]

```cpp showLineNumbers={false}
virtual nvidia::gxf::Clock * holoscan::MultiThreadScheduler::gxf_clock()
```

Get the GXF [Clock](../namespaces/gxf/classes/clock) pointer.

**Returns:** The GXF clock pointer used by the scheduler.

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

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

Get a `YAML` representation of the scheduler.

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

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

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

Reset any backend-specific objects.

### set\_parameters \[#setparameters]

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

Set the parameters based on defaults (sets GXF parameters for GXF operators).

### id \[#id]

#### Mutable

```cpp showLineNumbers={false}
Scheduler & holoscan::Scheduler::id(
    int64_t id
)
```

Set the [Scheduler](scheduler) ID.

**Returns:** The reference to this scheduler.

**Parameters**

The ID of the scheduler.

#### Const

const

```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.

### name \[#name]

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

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

Set the name of the scheduler.

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

**Parameters**

The name of the scheduler.

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

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

Set the name of the scheduler.

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

**Parameters**

The name of the scheduler.

#### 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 scheduler

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

Set the fragment of the scheduler.

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

**Parameters**

The pointer to the fragment of the scheduler.

#### 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 scheduler

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

Set the component specification to the scheduler.

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

**Parameters**

The component specification.

#### Get the component specification of the scheduler

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

Get the component specification of the scheduler.

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

### spec\_shared \[#specshared]

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

Get the shared pointer to the component spec.

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

### add\_arg \[#addarg]

#### Add a resource to the scheduler (1)

```cpp showLineNumbers={false}
void holoscan::Scheduler::add_arg(
    const std::shared_ptr<Resource> &arg
)
```

Add a resource to the scheduler.

**Parameters**

The resource to add.

#### Add a resource to the scheduler (2)

```cpp showLineNumbers={false}
void holoscan::Scheduler::add_arg(
    std::shared_ptr<Resource> &&arg
)
```

Add a resource to the scheduler.

**Parameters**

The resource to add.

#### 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**

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**

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**

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**

The list of arguments to add.

### resources \[#resources]

```cpp showLineNumbers={false}
std::unordered_map<std::string, std::shared_ptr<Resource>> & holoscan::Scheduler::resources()
```

Get the resources of the scheduler.

**Returns:** The resources of the scheduler.

### 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**

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**

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**

The type info of the service/resource to retrieve.

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()
```

### clock\_gxf\_cptr \[#clockgxfcptr]

```cpp showLineNumbers={false}
void * holoscan::MultiThreadScheduler::clock_gxf_cptr() const override
```

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

#### Update parameters based on the specified arguments

```cpp showLineNumbers={false}
void holoscan::Component::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**

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**

The type of the argument to register.

***

## Member variables

| Name                          | Type                                                             | Description                                       |
| ----------------------------- | ---------------------------------------------------------------- | ------------------------------------------------- |
| `clock_`                      | `Parameter< std::shared_ptr< gxf::Clock > >`                     |                                                   |
| `worker_thread_number_`       | `Parameter< int64_t >`                                           |                                                   |
| `stop_on_deadlock_`           | `Parameter< bool >`                                              |                                                   |
| `check_recession_period_ms_`  | `Parameter< double >`                                            |                                                   |
| `max_duration_ms_`            | `Parameter< int64_t >`                                           |                                                   |
| `stop_on_deadlock_timeout_`   | `Parameter< int64_t >`                                           |                                                   |
| `network_connection_timeout_` | `Parameter< int64_t >`                                           |                                                   |
| `strict_job_thread_pinning_`  | `Parameter< bool >`                                              |                                                   |
| `resources_`                  | `std::unordered_map< std::string, std::shared_ptr< Resource > >` | The resources used by the scheduler.              |
| `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 *`                                                         |                                                   |