PfHP Basics

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Unit 4.2.2 Basics

OpenMP is a standardized API (Application Programming Interface) for creating multiple threads of execution from a single program. For our purposes, you need to know very little:

There is a header file to include in the file(s):
```
#include <omp.h>
```

Directives to the compiler (pragmas):

#pragma omp parallel 
#pragma omp parallel for

A library of routines that can, for example, be used to inquire about the execution environment:
```
omp_get_max_threads() 
omp_get_num_threads() 
omp_get_thread_num()
```
Environment parameters that can be set before executing the program:
```
export OMP_NUM_THREADS=4
```
If you want to see what the value of this environment parameter is, execute
```
echo $OMP_NUM_THREADS
```

Learn more:

Search for "OpenMP" on Wikipedia.
Tim Mattson’s (Intel) “Introduction to OpenMP” (2013) on YouTube.
- Slides: Intro_To_OpenMP_Mattson.pdf
- Exercise files: Mattson_OMP_exercises.zip

We suggest you investigate OpenMP more after completing this week.