Difference between revisions of "OpenMP in Small Bites/Scoping"
OpenMP in Small Bites/Scoping
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| + | [[Category:Tutorials]] | ||
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| + | __TOC__ | ||
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{{Infobox OpenMP in Small Bites}} | {{Infobox OpenMP in Small Bites}} | ||
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| + | |||
| + | === Video === <!--T:5--> | ||
| + | |||
| + | <youtube width="600" height="400" right>IfD9IPixgpo</youtube> | ||
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| + | |||
| + | === Quiz === <!--T:5--> | ||
| + | |||
| + | {{hidden begin | ||
| + | |title = 1. What is the default data scoping of variable in a parallel region when this variable is declared before a parallel region? | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || shared | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
| + | |||
| + | {{hidden begin | ||
| + | |title = 2. What is the data scoping of the variables <code>a</code>, <code>b</code>, <code>c</code> and <code>d</code> in the following code snippet in the parallel region? What is printed when executing the code? | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || <code> int a = 0;<br /> int b = 23;<br /> int c = -3;<br /> # pragma omp parallel num_threads(2) private(a) reduction(+:c)<br /> { </code> <div style="margin-left: 1em;"><code>int d = omp_get_thread_num();<br /> a = 42 + d;<br /> # pragma omp critical<br /> b = 1;<br /> c += a + b;</code></div> <code>} <br />c = c / 2;<br /> printf("a=%d, b=%d, c=%d\n", a, b, c) </code><br /> {{Note|'''a: shared, b: private, c: firstprivate (due to the reduction clause), d: private <br />output: a=0, b=1, c=42'''}} | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
| + | |||
| + | {{hidden begin | ||
| + | |title = 3. The following code snippet is wrong due to a missing data sharing attribute. How can you fix it? | ||
| + | }} | ||
| + | <quiz display=simple> | ||
| + | { | ||
| + | |type="()"} | ||
| + | + Click and submit to see the answer | ||
| + | || <code> int i, int s = 0; <br /> # pragma omp parallel for <br /> for (i = 1; i < 100; i++){</code> <div style="margin-left: 1em;"><code> s = s + a[i];</code></div> <code>} </code> <br /> {{Note|'''Add <code>reduction(+:s)</code> clause to the parallel for construct'''}} | ||
| + | </quiz> | ||
| + | {{hidden end}} | ||
Revision as of 19:39, 30 October 2020
| HPC.NRW | |
|---|---|
 | |
| Other HPC Courses | |
| 1. | Gprof Tutorial |
| 2. | Introduction to Linux in HPC |
| OpenMP in Small Bites | |
| 1. | Overview |
| 2. | Worksharing |
| 3. | Data Scoping |
| 4. | Non-Uniform Memory Access
|
Video
Quiz
1. What is the default data scoping of variable in a parallel region when this variable is declared before a parallel region?
2. What is the data scoping of the variables
a, b, c and d in the following code snippet in the parallel region? What is printed when executing the code?
3. The following code snippet is wrong due to a missing data sharing attribute. How can you fix it?