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[[Category:Tutorials|Tasking and Data Scoping (OpenMP)]]<nowiki /> {{DISPLAYTITLE:Tasking and Data Scoping (OpenMP)}}<nowiki /> {{Syllabus OpenMP in Small Bites}}<nowiki /> __TOC__ This video deepens the knowledge of OpenMP Tasking and Data Scoping by using an example which includes typical scenarios. Furthermore, aspects of the lifetime of a variable are discussed. == Video == <youtube width="600" height="340" right>sK11P-AfUCM</youtube> ([[Media:hpc.nrw_06_Introduction-TaskingAndScoping.pdf | Slides as pdf]]) == Quiz == {{hidden begin |title = 1. Consider the following code snippet <code>int x = 42;</code><br/> <code>#pragma omp parallel private(x)</code><br/> <code>{</code><br/> <div style="margin-left: 1em;"><code> #pragma omp task</code></div> <div style="margin-left: 1em;"><code> {</code></div> <div style="margin-left: 2em;"><code> x = 3;</code></div> <div style="margin-left: 1em;"><code> }</code></div> <code>}</code><br/> <code>printf("x=%d\n", x);</code><br/> What is the data scope of <code>x</code> in the task region and what is printed at the end? }} <quiz display=simple> { |type="()"} + <code>firstprivate</code>, x=42 - <code>firstprivate</code>, x=3 - <code>shared</code>, x=3 </quiz> {{hidden end}} {{hidden begin |title = 2. Consider the following code snippet <code>int x = 42;</code><br/> <code>int y = 0;</code><br/> <code>#pragma omp parallel num_threads(4)</code><br/> <code>{</code><br/> <div style="margin-left: 1em;"><code> #pragma omp task</code></div> <div style="margin-left: 1em;"><code> {</code></div> <div style="margin-left: 2em;"><code> #pragma omp critical</code></div> <div style="margin-left: 2em;"><code> {</code></div> <div style="margin-left: 3em;"><code> y += x;</code></div> <div style="margin-left: 2em;"><code> }</code></div> <div style="margin-left: 1em;"><code> }</code></div> <code>}</code><br/> <code>printf("y=%d\n", y);</code><br/> What is the data scope of <code>x</code> in the task region and what is printed out at the end? }} <quiz display=simple> { |type="()"} - <code>shared</code>, y=42 + <code>shared</code>, y=168 - <code>firstprivate</code>, y=168 </quiz> {{hidden end}} {{hidden begin |title = 3. Consider the following code snippet <code>int x = 42;</code><br/> <code>int y = 0;</code><br/> <code>#pragma omp parallel num_threads(4)</code><br/> <code>{</code><br/> <div style="margin-left: 1em;"><code> #pragma omp single</code></div> <div style="margin-left: 1em;"><code> {</code></div> <div style="margin-left: 2em;"><code> #pragma omp task</code></div> <div style="margin-left: 2em;"><code> {</code></div> <div style="margin-left: 3em;"><code> #pragma omp critical</code></div> <div style="margin-left: 3em;"><code> {</code></div> <div style="margin-left: 4em;"><code> y += x;</code></div> <div style="margin-left: 3em;"><code> }</code></div> <div style="margin-left: 2em;"><code> }</code></div> <div style="margin-left: 1em;"><code> }</code></div> <code>}</code><br/> <code>printf("y=%d\n", y);</code><br/> What is the data scope of <code>x</code> in the task region and what is printed out at the end? }} <quiz display=simple> { |type="()"} + <code>shared</code>, y=42 - <code>shared</code>, y=168 - <code>firstprivate</code>, y=168 </quiz> {{hidden end}}

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