Event Management

Event Management#

HIP Runtime API Reference: Event Management
Event Management
Collaboration diagram for Event Management:

Functions

hipError_t hipEventCreateWithFlags (hipEvent_t *event, unsigned flags)
 Create an event with the specified flags.
 
hipError_t hipEventCreate (hipEvent_t *event)
 
hipError_t hipEventRecord (hipEvent_t event, hipStream_t stream=NULL)
 Record an event in the specified stream.
 
hipError_t hipEventDestroy (hipEvent_t event)
 Destroy the specified event.
 
hipError_t hipEventSynchronize (hipEvent_t event)
 Wait for an event to complete.
 
hipError_t hipEventElapsedTime (float *ms, hipEvent_t start, hipEvent_t stop)
 Return the elapsed time between two events.
 
hipError_t hipEventQuery (hipEvent_t event)
 Query event status.
 

Detailed Description



This section describes the event management functions of HIP runtime API.

Function Documentation

◆ hipEventCreate()

◆ hipEventCreateWithFlags()

hipError_t hipEventCreateWithFlags ( hipEvent_t event,
unsigned  flags 
)

Create an event with the specified flags.

Parameters
[in,out]eventReturns the newly created event.
[in]flagsFlags to control event behavior. Valid values are hipEventDefault, hipEventBlockingSync, hipEventDisableTiming, hipEventInterprocess hipEventDefault : Default flag. The event will use active synchronization and will support timing. Blocking synchronization provides lowest possible latency at the expense of dedicating a CPU to poll on the event. hipEventBlockingSync : The event will use blocking synchronization : if hipEventSynchronize is called on this event, the thread will block until the event completes. This can increase latency for the synchroniation but can result in lower power and more resources for other CPU threads. hipEventDisableTiming : Disable recording of timing information. Events created with this flag would not record profiling data and provide best performance if used for synchronization. hipEventInterprocess : The event can be used as an interprocess event. hipEventDisableTiming flag also must be set when hipEventInterprocess flag is set. hipEventDisableSystemFence : Disable acquire and release system scope fence. This may improve performance but device memory may not be visible to the host and other devices if this flag is set.
Returns
hipSuccess, hipErrorNotInitialized, hipErrorInvalidValue, hipErrorLaunchFailure, hipErrorOutOfMemory
See also
hipEventCreate, hipEventSynchronize, hipEventDestroy, hipEventElapsedTime

◆ hipEventDestroy()

hipError_t hipEventDestroy ( hipEvent_t  event)

Destroy the specified event.

Parameters
[in]eventEvent to destroy.
Returns
hipSuccess, hipErrorNotInitialized, hipErrorInvalidValue, hipErrorLaunchFailure

Releases memory associated with the event. If the event is recording but has not completed recording when hipEventDestroy() is called, the function will return immediately and the completion_future resources will be released later, when the hipDevice is synchronized.

See also
hipEventCreate, hipEventCreateWithFlags, hipEventQuery, hipEventSynchronize, hipEventRecord, hipEventElapsedTime
Returns
hipSuccess

◆ hipEventElapsedTime()

hipError_t hipEventElapsedTime ( float *  ms,
hipEvent_t  start,
hipEvent_t  stop 
)

Return the elapsed time between two events.

Parameters
[out]ms: Return time between start and stop in ms.
[in]start: Start event.
[in]stop: Stop event.
Returns
hipSuccess, hipErrorInvalidValue, hipErrorNotReady, hipErrorInvalidHandle, hipErrorNotInitialized, hipErrorLaunchFailure

Computes the elapsed time between two events. Time is computed in ms, with a resolution of approximately 1 us.

Events which are recorded in a NULL stream will block until all commands on all other streams complete execution, and then record the timestamp.

Events which are recorded in a non-NULL stream will record their timestamp when they reach the head of the specified stream, after all previous commands in that stream have completed executing. Thus the time that the event recorded may be significantly after the host calls hipEventRecord().

If hipEventRecord() has not been called on either event, then hipErrorInvalidHandle is returned. If hipEventRecord() has been called on both events, but the timestamp has not yet been recorded on one or both events (that is, hipEventQuery() would return hipErrorNotReady on at least one of the events), then hipErrorNotReady is returned.

See also
hipEventCreate, hipEventCreateWithFlags, hipEventQuery, hipEventDestroy, hipEventRecord, hipEventSynchronize

◆ hipEventQuery()

hipError_t hipEventQuery ( hipEvent_t  event)

Query event status.

Parameters
[in]eventEvent to query.
Returns
hipSuccess, hipErrorNotReady, hipErrorInvalidHandle, hipErrorInvalidValue, hipErrorNotInitialized, hipErrorLaunchFailure

Query the status of the specified event. This function will return hipSuccess if all commands in the appropriate stream (specified to hipEventRecord()) have completed. If any execution has not completed, then hipErrorNotReady is returned.

Note
This API returns hipSuccess, if hipEventRecord() is not called before this API.
See also
hipEventCreate, hipEventCreateWithFlags, hipEventRecord, hipEventDestroy, hipEventSynchronize, hipEventElapsedTime

◆ hipEventRecord()

hipError_t hipEventRecord ( hipEvent_t  event,
hipStream_t  stream = NULL 
)

Record an event in the specified stream.

Parameters
[in]eventevent to record.
[in]streamstream in which to record event.
Returns
hipSuccess, hipErrorInvalidValue, hipErrorNotInitialized, hipErrorInvalidHandle, hipErrorLaunchFailure

hipEventQuery() or hipEventSynchronize() must be used to determine when the event transitions from "recording" (after hipEventRecord() is called) to "recorded" (when timestamps are set, if requested).

Events which are recorded in a non-NULL stream will transition to from recording to "recorded" state when they reach the head of the specified stream, after all previous commands in that stream have completed executing.

If hipEventRecord() has been previously called on this event, then this call will overwrite any existing state in event.

If this function is called on an event that is currently being recorded, results are undefined

  • either outstanding recording may save state into the event, and the order is not guaranteed.
Note
If this function is not called before use hipEventQuery() or hipEventSynchronize(), hipSuccess is returned, meaning no pending event in the stream.
See also
hipEventCreate, hipEventCreateWithFlags, hipEventQuery, hipEventSynchronize, hipEventDestroy, hipEventElapsedTime

◆ hipEventSynchronize()

hipError_t hipEventSynchronize ( hipEvent_t  event)

Wait for an event to complete.

This function will block until the event is ready, waiting for all previous work in the stream specified when event was recorded with hipEventRecord().

If hipEventRecord() has not been called on event, this function returns hipSuccess when no event is captured.

Parameters
[in]eventEvent on which to wait.
Returns
hipSuccess, hipErrorInvalidValue, hipErrorNotInitialized, hipErrorInvalidHandle, hipErrorLaunchFailure
See also
hipEventCreate, hipEventCreateWithFlags, hipEventQuery, hipEventDestroy, hipEventRecord, hipEventElapsedTime