Difference between revisions of "OpenMP in Small Bites/Worksharing"
OpenMP in Small Bites/Worksharing
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| − | {{ | + | [[Category:Tutorials|Worksharing (OpenMP)]]<nowiki /> |
| + | {{DISPLAYTITLE:Worksharing (OpenMP)}}<nowiki /> | ||
| + | {{Syllabus OpenMP in Small Bites}}<nowiki /> | ||
| + | __TOC__ | ||
| + | |||
| + | This video shows the concept of OpenMP worksharing, loop scheduling and synchronization mechanisms. After this tutorial session the programmer already has knowledge about the most common used OpenMP constructs and API functions. How the scoping of data is controlled is introduced in the part on [[OpenMP_in_Small_Bites/Scoping |Data Scoping]]. | ||
| + | |||
| + | === Video === <!--T:5--> | ||
| + | |||
| + | <youtube width="600" height="340" right>vIX0Zplc2ws</youtube> | ||
| + | |||
| + | ([[Media:hpc.nrw_02_Introduction-Worksharing.pdf | Slides as pdf]]) | ||
| + | |||
| + | === Quiz === <!--T:5--> | ||
| + | |||
| + | |||
| + | {{hidden begin | ||
| + | |title = 1. What is most commonly used worksharing construct in OpenMP to distribute work among loop interations? | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || C/C++: for-construct <code>#pragma omp for </code>(or as combined construct <code>#pragma omp parallel for </code> <br /> Fortran: do-construct <code>!$omp do</code> | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
| + | |||
| + | {{hidden begin | ||
| + | |title = 2. Give an example for a parallel vector addition using OpenMP worksharing! | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || C/C++:<br /><code>int i; <br />#pragma omp parallel <br />#pragma omp for <br /> for (i = 0; i < 100; i++){</code> <div style="margin-left: 1em;"> <code> a[i] = b[i] + c[i]; </code> </div> <code> } </code> <br /> Fortran:<br /> <code> INTEGER :: i <br />!$omp parallel <br />!$omp do <br /> DO i = 0, 99</code> <div style="margin-left: 1em;"> <code> a[i] = b[i] + c[i] </code> </div><code>END DO </code> | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
| + | |||
| + | |||
| + | {{hidden begin | ||
| + | |title = 3. Can the following code snipped be parallelized with the OpenMP for-construct with out breaking the semantic? Justify your answer. <br> | ||
| + | <code> int i, int s = 0; <br /> for (i = 1; i < 100; i++){ </code> <div style="margin-left: 1em;"><code> s = a[i-1] + a[i]; </code></div> <code>} </code> <br /> | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || {{Note|'''No. Due to the dependency between the loop iterations this would cause a data race'''}} | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
Latest revision as of 17:29, 4 December 2020
| Tutorial | |
|---|---|
| Title: | OpenMP in Small Bites |
| Provider: | HPC.NRW
|
| Contact: | tutorials@hpc.nrw |
| Type: | Multi-part video |
| Topic Area: | Programming Paradigms |
| License: | CC-BY-SA |
| Syllabus
| |
| 1. Overview | |
| 2. Worksharing | |
| 3. Data Scoping | |
| 4. False Sharing | |
| 5. Tasking | |
| 6. Tasking and Data Scoping | |
| 7. Tasking and Synchronization | |
| 8. Loops and Tasks | |
| 9. Tasking Example: Sudoku Solver | |
| 10. Task Scheduling | |
| 11. Non-Uniform Memory Access | |
This video shows the concept of OpenMP worksharing, loop scheduling and synchronization mechanisms. After this tutorial session the programmer already has knowledge about the most common used OpenMP constructs and API functions. How the scoping of data is controlled is introduced in the part on Data Scoping.
Video
Quiz
Collapse
1. What is most commonly used worksharing construct in OpenMP to distribute work among loop interations?
Collapse
3. Can the following code snipped be parallelized with the OpenMP for-construct with out breaking the semantic? Justify your answer.
int i, int s = 0;
for (i = 1; i < 100; i++){ s = a[i-1] + a[i]; }