OpenCL Runtime: Command Queues and Events

Command Queue

class pyopencl.CommandQueue(context, device=None, properties=None)

Create a new command queue. properties is a bit field consisting of command_queue_properties values.

if device is None, one of the devices in context is chosen in an implementation-defined manner.

A CommandQueue may be used as a context manager, like this:

with cl.CommandQueue(self.cl_context) as queue:
    enqueue_stuff(queue, ...)

finish() is automatically called at the end of the context.

New in version 2013.1: Context manager capability.

info

Lower case versions of the command_queue_info constants may be used as attributes on instances of this class to directly query info attributes.

get_info(param)

See command_queue_info for values of param.

set_property(prop, enable)

See command_queue_properties for possible values of prop. enable is a bool.

Unavailable in OpenCL 1.1 and newer.

flush()
finish()
from_int_ptr(int_ptr_value, retain=True)

Constructs a pyopencl handle from a C-level pointer (given as the integer int_ptr_value). If retain is True (the defauult) pyopencl will call clRetainXXX on the provided object. If the previous owner of the object will not release the reference, retain should be set to False, to effectively transfer ownership to pyopencl.

Changed in version 2016.1: retain added

int_ptr

Instances of this class are hashable, and two instances of this class may be compared using “==” and ”!=”. (Hashability was added in version 2011.2.) Two objects are considered the same if the underlying OpenCL object is the same, as established by C pointer equality.

Event

class pyopencl.Event
info

Lower case versions of the event_info constants may be used as attributes on instances of this class to directly query info attributes.

profile.info

Lower case versions of the profiling_info constants may be used as attributes on the attribute profile of this class to directly query profiling info.

For example, you may use evt.profile.end instead of evt.get_profiling_info(pyopencl.profiling_info.END).

get_info(param)

See event_info for values of param.

get_profiling_info(param)

See profiling_info for values of param. See profile for an easier way of obtaining the same information.

wait()
from_int_ptr(int_ptr_value, retain=True)

Constructs a pyopencl handle from a C-level pointer (given as the integer int_ptr_value). If retain is True (the defauult) pyopencl will call clRetainXXX on the provided object. If the previous owner of the object will not release the reference, retain should be set to False, to effectively transfer ownership to pyopencl.

Changed in version 2016.1: retain added

int_ptr
set_callback(type, cb)

Add the callback cb with signature cb(status) to the callback queue for the event status type (one of the values of command_execution_status, except command_execution_status.QUEUED).

See the OpenCL specification for restrictions on what cb may and may not do.

New in version 2015.2.

Instances of this class are hashable, and two instances of this class may be compared using “==” and ”!=”. (Hashability was added in version 2011.2.) Two objects are considered the same if the underlying OpenCL object is the same, as established by C pointer equality.

Event Subclasses

class pyopencl.UserEvent(context)

A subclass of Event. Only available with OpenCL 1.1 and newer.

New in version 0.92.

set_status(status)

See command_execution_status for possible values of status.

class pyopencl.NannyEvent

Transfers between host and device return events of this type. They hold a reference to the host-side buffer and wait for the transfer to complete when they are freed. Therefore, they can safely release the reference to the object they’re guarding upon destruction.

A subclass of Event.

New in version 2011.2.

get_ward()
wait()

In addition to performing the same wait as Event.wait(), this method also releases the reference to the guarded object.

Synchronization Functions

pyopencl.wait_for_events(events)
pyopencl.enqueue_barrier(queue, wait_for=None)

Enqueues a barrier operation. which ensures that all queued commands in command_queue have finished execution. This command is a synchronization point.

New in version 0.91.5.

Changed in version 2011.2: Takes wait_for and returns an Event

pyopencl.enqueue_marker(queue, wait_for=None)

Returns an Event.

Changed in version 2011.2: Takes wait_for.