introduction-to-openmp

Hello World

#without fopenmp

gcc OMP-hello.c -o OMP-helloOM -fopenmp

./OMP-helloOM

gcc OMP-hello.c -o OMP-hello

./OMP-hello

export OMP_NUM_THREADS=3

./OMP-hello

Execution script

#!/bin/bash

#SBATCH -c 8

./exec.sh

Function

gcc OMP-hello-function.c -o OMP-hello-function -fopenmp
OMP-hello-function./OMP-hello-function

Thread Affinity

export OMP_NUM_THREADS=10
export GOMP_CPU_AFFINITY=0-10
./fib-taskOM

export OMP_PROC_BIND=spread
./fib-taskOM
export OMP_PROC_BIND=close
./fib-taskOM

Data Sharing Clauses

OMP-hello-function
gcc OMP-hello-PR-variable.c -o OMP-hello-PR-variable -fopenmp
./OMP-hello-PR-variable

Loop Worksharing

gcc OMP-loop-WorkSharing.c -o OMP-loop-WorkSharing -fopenmp

Performance Comparison

Serial version:

gcc OMP-matrix-sum.c -o OMP-matrix-sum

time ./OMP-matrix-sum

Parallel version:

gcc OMP-matrix-sum.c -o OMP-matrix-sumOM -fopenmp

time ./OMP-matrix-sumOM

Race condition

gcc OMP-race.c -o OMP-race -fopenmp
./OMP-race

Race condition - synchronization

critical, atomic, ordered

gcc OMP-race.c -o OMP-race -fopenmp
./OMP-race

Synchronization

gcc OMP-sync.c -o OMP-sync -fopenmp

./OMP-sync

Task

gcc OMP-task.c -o OMP-task

./OMP-task 

Fibonacci

gcc fib-task.c -o fib-task 

./fib-task 

gcc fib-task.c -o fib-taskOM -fopenmp

./fib-taskOM