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Add WorkerThreadPool documentation

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VolTer 2023-04-28 05:23:59 +02:00
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doc/classes/WorkerThreadPool.xml
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@ -1,10 +1,50 @@
<?xml version="1.0" encoding="UTF-8" ?>
<class name="WorkerThreadPool" inherits="Object" version="4.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
<brief_description>
A singleton that allocates some [Thread]s on startup, used to offload tasks to these threads.
</brief_description>
<description>
The [WorkerThreadPool] singleton allocates a set of [Thread]s (called worker threads) on project startup and provides methods for offloading tasks to them. This can be used for simple multithreading without having to create [Thread]s.
Tasks hold the [Callable] to be run by the threads. [WorkerThreadPool] can be used to create regular tasks, which will be taken by one worker thread, or group tasks, which can be distributed between multiple worker threads. Group tasks execute the [Callable] multiple times, which makes them useful for iterating over a lot of elements, such as the enemies in an arena.
Here's a sample on how to offload an expensive function to worker threads:
[codeblocks]
[gdscript]
var enemies = [] # An array to be filled with enemies.
func process_enemy_ai(enemy_index):
var processed_enemy = enemies[enemy_index]
# Expensive logic...
func _process(delta):
var task_id = WorkerThreadPool.add_group_task(process_enemy_ai, enemies.size())
# Other code...
WorkerThreadPool.wait_for_group_task_completion(task_id)
# Other code that depends on the enemy AI already being processed.
[/gdscript]
[csharp]
private List&lt;Node&gt; _enemies = new List&lt;Node&gt;(); // A list to be filled with enemies.
private void ProcessEnemyAI(int enemyIndex)
{
Node processedEnemy = _enemies[enemyIndex];
// Expensive logic here.
}
public override void _Process(double delta)
{
long taskId = WorkerThreadPool.AddGroupTask(Callable.From&lt;int&gt;(ProcessEnemyAI), _enemies.Count);
// Other code...
WorkerThreadPool.WaitForGroupTaskCompletion(taskId);
// Other code that depends on the enemy AI already being processed.
}
[/csharp]
[/codeblocks]
The above code relies on the number of elements in the [code]enemies[/code] array remaining constant during the multithreaded part.
[b]Note:[/b] Using this singleton could affect performance negatively if the task being distributed between threads is not computationally expensive.
</description>
<tutorials>
<link title="Using multiple threads">$DOCS_URL/tutorials/performance/using_multiple_threads.html</link>
<link title="Thread-safe APIs">$DOCS_URL/tutorials/performance/thread_safe_apis.html</link>
</tutorials>
<methods>
<method name="add_group_task">
@ -15,6 +55,9 @@
<param index="3" name="high_priority" type="bool" default="false" />
<param index="4" name="description" type="String" default="&quot;&quot;" />
<description>
Adds [param action] as a group task to be executed by the worker threads. The [Callable] will be called a number of times based on [param elements], with the first thread calling it with the value [code]0[/code] as a parameter, and each consecutive execution incrementing this value by 1 until it reaches [code]element - 1[/code].
The number of threads the task is distributed to is defined by [param tasks_needed], where the default value [code]-1[/code] means it is distributed to all worker threads. [param high_priority] determines if the task has a high priority or a low priority (default). You can optionally provide a [param description] to help with debugging.
Returns a group task ID that can be used by other methods.
</description>
</method>
<method name="add_task">
@ -23,36 +66,44 @@
<param index="1" name="high_priority" type="bool" default="false" />
<param index="2" name="description" type="String" default="&quot;&quot;" />
<description>
Adds [param action] as a task to be executed by a worker thread. [param high_priority] determines if the task has a high priority or a low priority (default). You can optionally provide a [param description] to help with debugging.
Returns a task ID that can be used by other methods.
</description>
</method>
<method name="get_group_processed_element_count" qualifiers="const">
<return type="int" />
<param index="0" name="group_id" type="int" />
<description>
Returns how many times the [Callable] of the group task with the given ID has already been executed by the worker threads.
[b]Note:[/b] If a thread has started executing the [Callable] but is yet to finish, it won't be counted.
</description>
</method>
<method name="is_group_task_completed" qualifiers="const">
<return type="bool" />
<param index="0" name="group_id" type="int" />
<description>
Returns [code]true[/code] if the group task with the given ID is completed.
</description>
</method>
<method name="is_task_completed" qualifiers="const">
<return type="bool" />
<param index="0" name="task_id" type="int" />
<description>
Returns [code]true[/code] if the task with the given ID is completed.
</description>
</method>
<method name="wait_for_group_task_completion">
<return type="void" />
<param index="0" name="group_id" type="int" />
<description>
Pauses the thread that calls this method until the group task with the given ID is completed.
</description>
</method>
<method name="wait_for_task_completion">
<return type="void" />
<param index="0" name="task_id" type="int" />
<description>
Pauses the thread that calls this method until the task with the given ID is completed.
</description>
</method>
</methods>