Functions

__host__ ​cudaError_t cudaEventCreate ( cudaEvent_t* event )

Creates an event object.

Parameters

event

- Newly created event

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorLaunchFailure, cudaErrorMemoryAllocation

Description

Creates an event object for the current device using cudaEventDefault.

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

See also:

cudaEventCreate ( C++ API), cudaEventCreateWithFlags, cudaEventRecord, cudaEventQuery, cudaEventSynchronize, cudaEventDestroy, cudaEventElapsedTime, cudaStreamWaitEvent, cuEventCreate

__host__ ​ __device__ ​cudaError_t cudaEventCreateWithFlags ( cudaEvent_t* event, unsigned int  flags )

Creates an event object with the specified flags.

Parameters

event

- Newly created event

flags

- Flags for new event

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorLaunchFailure, cudaErrorMemoryAllocation

Description

Creates an event object for the current device with the specified flags. Valid flags include:

• cudaEventDefault: Default event creation flag.

• cudaEventBlockingSync: Specifies that event should use blocking synchronization. A host thread that uses cudaEventSynchronize() to wait on an event created with this flag will block until the event actually completes.

• cudaEventDisableTiming: Specifies that the created event does not need to record timing data. Events created with this flag specified and the cudaEventBlockingSync flag not specified will provide the best performance when used with cudaStreamWaitEvent() and cudaEventQuery().

• cudaEventInterprocess: Specifies that the created event may be used as an interprocess event by cudaIpcGetEventHandle(). cudaEventInterprocess must be specified along with cudaEventDisableTiming.

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

See also:

cudaEventCreate ( C API), cudaEventSynchronize, cudaEventDestroy, cudaEventElapsedTime, cudaStreamWaitEvent, cuEventCreate

__host__ ​ __device__ ​cudaError_t cudaEventDestroy ( cudaEvent_t event )

Destroys an event object.

Parameters

event

- Event to destroy

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure

Description

Destroys the event specified by event.

An event may be destroyed before it is complete (i.e., while cudaEventQuery() would return cudaErrorNotReady). In this case, the call does not block on completion of the event, and any associated resources will automatically be released asynchronously at completion.

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Use of the handle after this call is undefined behavior.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventQuery, cudaEventSynchronize, cudaEventRecord, cudaEventElapsedTime, cuEventDestroy

__host__ ​cudaError_t cudaEventElapsedTime ( float* ms, cudaEvent_t start, cudaEvent_t end )

Computes the elapsed time between events.

Parameters

ms

- Time between start and end in ms

start

- Starting event

end

- Ending event

Returns

cudaSuccess, cudaErrorNotReady, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure, cudaErrorUnknown

Description

Computes the elapsed time between two events (in milliseconds with a resolution of around 0.5 microseconds).

If either event was last recorded in a non-NULL stream, the resulting time may be greater than expected (even if both used the same stream handle). This happens because the cudaEventRecord() operation takes place asynchronously and there is no guarantee that the measured latency is actually just between the two events. Any number of other different stream operations could execute in between the two measured events, thus altering the timing in a significant way.

If cudaEventRecord() has not been called on either event, then cudaErrorInvalidResourceHandle is returned. If cudaEventRecord() has been called on both events but one or both of them has not yet been completed (that is, cudaEventQuery() would return cudaErrorNotReady on at least one of the events), cudaErrorNotReady is returned. If either event was created with the cudaEventDisableTiming flag, then this function will return cudaErrorInvalidResourceHandle.

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventQuery, cudaEventSynchronize, cudaEventDestroy, cudaEventRecord, cuEventElapsedTime

__host__ ​cudaError_t cudaEventQuery ( cudaEvent_t event )

Queries an event's status.

Parameters

event

- Event to query

Returns

cudaSuccess, cudaErrorNotReady, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure

Description

Queries the status of all work currently captured by event. See cudaEventRecord() for details on what is captured by an event.

Returns cudaSuccess if all captured work has been completed, or cudaErrorNotReady if any captured work is incomplete.

For the purposes of Unified Memory, a return value of cudaSuccess is equivalent to having called cudaEventSynchronize().

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventRecord, cudaEventSynchronize, cudaEventDestroy, cudaEventElapsedTime, cuEventQuery

__host__ ​ __device__ ​cudaError_t cudaEventRecord ( cudaEvent_t event, cudaStream_t stream = 0 )

Records an event.

Parameters

event

- Event to record

stream

- Stream in which to record event

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure

Description

Captures in event the contents of stream at the time of this call. event and stream must be on the same CUDA context. Calls such as cudaEventQuery() or cudaStreamWaitEvent() will then examine or wait for completion of the work that was captured. Uses of stream after this call do not modify event. See note on default stream behavior for what is captured in the default case.

cudaEventRecord() can be called multiple times on the same event and will overwrite the previously captured state. Other APIs such as cudaStreamWaitEvent() use the most recently captured state at the time of the API call, and are not affected by later calls to cudaEventRecord(). Before the first call to cudaEventRecord(), an event represents an empty set of work, so for example cudaEventQuery() would return cudaSuccess.

Note:

• This function uses standard default stream semantics.

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventQuery, cudaEventSynchronize, cudaEventDestroy, cudaEventElapsedTime, cudaStreamWaitEvent, cudaEventRecordWithFlags, cuEventRecord

__host__ ​cudaError_t cudaEventRecordWithFlags ( cudaEvent_t event, cudaStream_t stream = 0, unsigned int  flags = 0 )

Records an event.

Parameters

event

- Event to record

stream

- Stream in which to record event

flags

- Parameters for the operation(See above)

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure

Description

Captures in event the contents of stream at the time of this call. event and stream must be on the same CUDA context. Calls such as cudaEventQuery() or cudaStreamWaitEvent() will then examine or wait for completion of the work that was captured. Uses of stream after this call do not modify event. See note on default stream behavior for what is captured in the default case.

cudaEventRecordWithFlags() can be called multiple times on the same event and will overwrite the previously captured state. Other APIs such as cudaStreamWaitEvent() use the most recently captured state at the time of the API call, and are not affected by later calls to cudaEventRecordWithFlags(). Before the first call to cudaEventRecordWithFlags(), an event represents an empty set of work, so for example cudaEventQuery() would return cudaSuccess.

flags include:

• cudaEventRecordDefault: Default event creation flag.

• cudaEventRecordExternal: Event is captured in the graph as an external event node when performing stream capture.

Note:

• This function uses standard default stream semantics.

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventQuery, cudaEventSynchronize, cudaEventDestroy, cudaEventElapsedTime, cudaStreamWaitEvent, cudaEventRecord, cuEventRecord,

__host__ ​cudaError_t cudaEventSynchronize ( cudaEvent_t event )

Waits for an event to complete.

Parameters

event

- Event to wait for

Returns

cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle, cudaErrorLaunchFailure

Description

Waits until the completion of all work currently captured in event. See cudaEventRecord() for details on what is captured by an event.

Waiting for an event that was created with the cudaEventBlockingSync flag will cause the calling CPU thread to block until the event has been completed by the device. If the cudaEventBlockingSync flag has not been set, then the CPU thread will busy-wait until the event has been completed by the device.

Note:

• Note that this function may also return error codes from previous, asynchronous launches.

• Note that this function may also return cudaErrorInitializationError, cudaErrorInsufficientDriver or cudaErrorNoDevice if this call tries to initialize internal CUDA RT state.

• Note that as specified by cudaStreamAddCallback no CUDA function may be called from callback. cudaErrorNotPermitted may, but is not guaranteed to, be returned as a diagnostic in such case.

• Returns cudaErrorInvalidResourceHandle in the event of being passed NULL as the input event.

See also:

cudaEventCreate ( C API), cudaEventCreateWithFlags, cudaEventRecord, cudaEventQuery, cudaEventDestroy, cudaEventElapsedTime, cuEventSynchronize