View source for OpenMP in Small Bites/Overview

[[Category:Tutorials]]<nowiki />
{{DISPLAYTITLE:OpenMP Overview}}
{{Syllabus OpenMP in Small Bites}}<nowiki />
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This video provides a brief history of OpenMP and then introduces the parallel region, one of the most fundamental concepts of OpenMP, used to mark code regions that are meant to be processed by multiple threads in parallel. How the code region is processed and by which threads is then controlled by other OpenMP constructs introduced in the part on [[OpenMP in Small Bites/Worksharing | Worksharing]].

=== Video === <!--T:5-->

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

([[Media:hpc.nrw_01_Introduction-Overview.pdf | Slides as pdf]])

=== Quiz === <!--T:5-->  


{{hidden begin 
|title = 1. Out of which three components does the OpenMP interface consist?
}}
<quiz display=simple>
{
|type="()"}
+ Compiler directives, runtime routines, environment variables
|| Correct
- Compiler directives, host language extensions, runtime routines
|| While compiler support is needed, OpenMP does comprise host language extensions, yet also uses environment variables.
- Host language extensions, runtime routines, environment variables.
|| OpenMP does not comprise host language extensions, but rather uses compiler directives to insert .
</quiz>
{{hidden end}}

{{hidden begin 
|title = 2. What is one of the key concepts of the OpenMP execution model?
}}
<quiz display=simple>
{
|type="()"}
+ Fork-Join
||  An OpenMP program starts with just one worker thread (<code>master</code>). The <code>worker</code> threads are spawned in the parallel region and form a <code>team</code> of threads together with the <code>master</code>. They all join at the end of a parallel region. 
- Create-Release
||  An OpenMP program starts with just one worker thread (<code>master</code>). The <code>worker</code> threads are spawned in the parallel region and form a <code>team</code> of threads together with the <code>master</code>. They all join at the end of a parallel region. 
- Start-Wait
|| An OpenMP program starts with just one worker thread (<code>master</code>). The <code>worker</code> threads are spawned in the parallel region and form a <code>team</code> of threads together with the <code>master</code>. They all join at the end of a parallel region. 
</quiz>
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{{hidden begin 
|title = 3. How can you control the number of threads?
}}
<quiz display=simple>
{
|type="[]"}
+ Set environment variable <code>OMP_NUM_THREADS</code>.
|| True
+ Use <code>num_threads</code> clause on a parallel construct.
|| True
- Number of threads are fixed at compile time
|| False
- All of the above
|| False
</quiz>
{{hidden end}}