Function: launch_callback

Applicability

Product	Supported (√/x)
Atlas A3 training products / Atlas A3 inference products	√
Atlas A2 training products / Atlas A2 inference products	√
Atlas training products	√
Atlas inference products	√
Atlas 200I/500 A2 inference products	√

Function Usage

Delivers a callback task in the task queue of the stream in the asynchronous task scenario. When the callback task is executed in the system, it is also executed in the thread subscribed to on the stream (acl.rt.subscribe_report). This API is asynchronous.

This API must be work with the following APIs to implement the callback function in asynchronous scenarios:

Create a thread. Once acl.rt.process_report in the thread function is called to set the timeout interval (cyclic calling is required), acl.rt.launch_callback will deliver a callback task after a period of time.
Call acl.rt.subscribe_report to bind the thread created in Step 1 to the stream. The callback task delivered by the stream is executed in the bound thread.
Execute an asynchronous job (for example, an asynchronous inference job) on the specified stream.
Define and implement the callback function, call acl.rt.launch_callback to deliver a callback task in the task queue of the stream, and trigger the thread to process the callback function subscribed by acl.rt.subscribe_report. Each time acl.rt.launch_callback is called, a callback task is delivered.
Call acl.rt.unsubscribe_report to unsubscribe from threads and unbind threads from streams after all asynchronous tasks are executed.

Prototype

C Prototype

        
             aclError aclrtLaunchCallback(aclrtCallback fn, void *userData, aclrtCallbackBlockType blockType, aclrtStream stream)

Python Function

        
             ret = acl.rt.launch_callback(fn, user_data_list,  block_type, stream)

Parameter Description

Parameter	Description
fn	Function, callback function on the Python side.
user_data_list	List, parameters to be transferred to the callback function. Currently, data of the list type is transferred.
block_type	Int, whether the callback task blocks subsequent tasks in the stream. 0: not blocked. 1: blocked.
stream	Int, stream.

Return Value Description

Return Value	Description
ret	Int, error code: 0 on success; else, failure.

Restrictions

This API is asynchronous. The API call delivers a task rather than executes a task. After this API is called, call the synchronization API (for example, acl.rt.synchronize_stream) to ensure that the task is complete.

Reference

For the API call sequence, see API Call Sequence.
For the API call example, see Sample Code.

Parent topic: Execution Control