Difference between revisions of "OpenMP in Small Bites/Tasking and Data Scoping"
OpenMP in Small Bites/Tasking and Data Scoping
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== Quiz == | == 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/> | ||
+ | <code> #pragma omp task</code><br/> | ||
+ | <code> {</code><br/> | ||
+ | <code> x = 3;</code><br/> | ||
+ | <code> }</code><br/> | ||
+ | <code>}</code><br/> | ||
+ | <code>printf("x=%d\n", x);</code><br/> | ||
+ | |||
+ | What is the data scope of <code>x</code> and what is printed? | ||
+ | }} | ||
+ | <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/> | ||
+ | <code> #pragma omp task</code><br/> | ||
+ | <code> {</code><br/> | ||
+ | <code> y += x;</code><br/> | ||
+ | <code> }</code><br/> | ||
+ | <code>}</code><br/> | ||
+ | <code>printf("y=%d\n", y);</code><br/> | ||
+ | |||
+ | What is the data scope of <code>x</code> and what is printed? | ||
+ | |||
+ | }} | ||
+ | <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/> | ||
+ | <code> #pragma omp single</code><br/> | ||
+ | <code> {</code><br/> | ||
+ | <code> #pragma omp task</code><br/> | ||
+ | <code> {</code><br/> | ||
+ | <code> y += x;</code><br/> | ||
+ | <code> }</code><br/> | ||
+ | <code> }</code><br/> | ||
+ | <code>}</code><br/> | ||
+ | <code>printf("y=%d\n", y);</code><br/> | ||
+ | |||
+ | What is the data scope of <code>x</code> and what is printed? | ||
+ | }} | ||
+ | <quiz display=simple> | ||
+ | { | ||
+ | |type="()"} | ||
+ | + <code>shared</code>, y=42 | ||
+ | - <code>shared</code>, y=168 | ||
+ | - <code>firstprivate</code>, y=168 | ||
+ | </quiz> | ||
+ | {{hidden end}} |
Revision as of 17:59, 30 November 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 |
Video
Quiz
1. Consider the following code snippet
int x = 42;
#pragma omp parallel private(x)
{
#pragma omp task
{
x = 3;
}
}
printf("x=%d\n", x);
x
and what is printed?
2. Consider the following code snippet
int x = 42;
int y = 0;
#pragma omp parallel num_threads(4)
{
#pragma omp task
{
y += x;
}
}
printf("y=%d\n", y);
x
and what is printed?
3. Consider the following code snippet
int x = 42;
int y = 0;
#pragma omp parallel num_threads(4)
{
#pragma omp single
{
#pragma omp task
{
y += x;
}
}
}
printf("y=%d\n", y);
x
and what is printed?