View source for OpenMP in Small Bites/Tasking

[[Category:Tutorials|Tasking (OpenMP)]]<nowiki />
{{DISPLAYTITLE:Tasking (OpenMP)}}<nowiki />
{{Syllabus OpenMP in Small Bites}}<nowiki />
__TOC__

This video introduces another way to to express parallelism in OpenMP: Tasking. This concept enables the programmer to parallelize code regions with non-canonical loop forms or regions which do not use loops at all (including recursive algorithms). The video explains how to use OpenMP tasking, how to synchonize, how to deal with cut-off strategies and how an OpenMP runtime environment manages the tasks in queues. More examples and details about [[OpenMP_in_Small_Bites/Tasking_and_Data_Scoping|Tasking and Data Scoping]] as well as [[OpenMP_in_Small_Bites/Tasking_and_Synchronization| Tasking_and_Synchronization]] are given in further parts of this tutorial.

== Video ==

<youtube width="600" height="340" right>lALAUBDszrU</youtube>

([[Media:Hpc.nrw_05_Introduction-Tasking.pdf | Slides as pdf]])

== Quiz ==
{{hidden begin 
|title = 1. What is the default data scoping of a variable in a task scope? Hint: Assume that the variable is declared before the task region, but in the same function.
}}
<quiz display=simple>
{
|type="()"}
- Always <code>firstprivate</code>.
|| Wrong.
+ <code>firstprivate</code> unless <code>shared</code> in the enclosing context.
|| Correct.
- <code>shared</code> unless <code>firstprivate</code> in the enclosing context.
|| Correct.
</quiz>
{{hidden end}}

{{hidden begin 
|title = 2. Which tasks are synchronized with by a <code>taskwait</code> construct?
}}
<quiz display=simple>
{
|type="()"}
- All tasks of the same thread team.
|| 
- All desendant tasks.
|| 
+ The direct child tasks.
||
</quiz>
{{hidden end}}

{{hidden begin 
|title = 3. Why can it be beneficial for the performance to use cut-off strategies for task-based OpenMP programs?
}}
<quiz display=simple>
{
|type="()"}
+ It can avoid overhead caused by too fine-grained tasks.
|| Correct.
- It can synchronize tasks faster.
|| Wrong.
- It can accelerate task stealing be enforcing one task queue per thread. 
|| Wrong.
</quiz>
{{hidden end}}