Difference between revisions of "OpenMP in Small Bites/Tasking and Data Scoping"

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OpenMP in Small Bites/Tasking and Data Scoping
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<code>printf("y=%d\n", y);</code><br/>
 
<code>printf("y=%d\n", y);</code><br/>
  
What is the data scope of <code>x</code> and what is printed?
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What is the data scope of <code>x</code> in the task region and what is printed out at the end?
  
 
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<code>printf("y=%d\n", y);</code><br/>
 
<code>printf("y=%d\n", y);</code><br/>
  
What is the data scope of <code>x</code> and what is printed?
+
What is the data scope of <code>x</code> in the task region and what is printed out at the end?
 
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<quiz display=simple>
 
<quiz display=simple>

Revision as of 19:04, 3 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 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


( Slides as pdf)

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);

What is the data scope of x in the task region and what is printed at the end?

firstprivate, x=42
firstprivate, x=3
shared, x=3

2. Consider the following code snippet

int x = 42;
int y = 0;
#pragma omp parallel num_threads(4)
{

#pragma omp task
{
#pragma omp critical
{
y += x;
}
}

}
printf("y=%d\n", y);

What is the data scope of x in the task region and what is printed out at the end?

shared, y=42
shared, y=168
firstprivate, y=168

3. Consider the following code snippet

int x = 42;
int y = 0;
#pragma omp parallel num_threads(4)
{

#pragma omp single
{
#pragma omp task
{
#pragma omp critical
{
y += x;
}
}
}

}
printf("y=%d\n", y);

What is the data scope of x in the task region and what is printed out at the end?

shared, y=42
shared, y=168
firstprivate, y=168