Task execution

This section provides a deeper look into the technical background concerning scheduling and task execution. The execution model of the UFO framework is based on the Ufo.TaskGraph that represents a network of interconnected task nodes and the Ufo.BaseScheduler that runs these tasks according to a pre-defined strategy. The Ufo.Scheduler is a concrete implementation and is the default choice because it is able to instantiate tasks in a multi-GPU environment. For greater flexibility, the Ufo.FixedScheduler can be used to define arbitrary GPU mappings.

Profiling execution

By default, the scheduler measures the run-time from initial setup until processing of the last data item finished. You can get the time in seconds via the time property

g = Ufo.TaskGraph()
scheduler = Ufo.Scheduler()
print("Time spent: {}s".format(scheduler.time))

To get more fine-grained insight into the execution, you can enable tracing

scheduler.props.enable_tracing = True

and analyse the generated traces for OpenCL (saved in opencl.PID.json) and general events (saved in trace.PID.json). To visualize the trace events, you can either use the distributed ufo-prof tool or Google Chrome or Chromium by going to chrome://tracing and loading the JSON files.

Broadcasting results

Connecting a task output to multiple consumers will in most cases cause undefined results because some data is processed differently than others. A certain class of problems can be solved by inserting explicit Ufo.CopyTask nodes and executing the graph with a Ufo.FixedScheduler. In the following example, we want write the same data twice with a different prefix:

from gi.repository import Ufo

pm = Ufo.PluginManager()
sched = Ufo.FixedScheduler()
graph = Ufo.TaskGraph()
copy = Ufo.CopyTask()

data = pm.get_task('read')

write1 = pm.get_task('write')

write2 = pm.get_task('write')

graph.connect_nodes(data, copy)
graph.connect_nodes(copy, write1)
graph.connect_nodes(copy, write2)



The copy task node is not a regular plugin but part of the core API and thus cannot be used with tools like ufo-runjson or ufo-launch.