OpenMP training
Table of Contents
Setup
Installation
apt-get install libopenmpi-dev
apt-get install openmpi-bin
Compilation & Running OpenMP
gcc -o name name.c -fopenmp
./name
Compilation & Running MPI
mpicc filename.c -o filename
mpirun -np 1 ./filename # -lm
Exercises
omp_threadnum.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
printf("Hello World from thread = %d\n", omp_get_thread_num());
}
omp_threadnum.c - exercises
omp_hello.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
{
printf("Hello World from thread = %d\n", omp_get_thread_num());
}
}
omp_hello.c - exercises
omp_private.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
int tid, nthreads;
/* Fork a team of threads */
#pragma omp parallel
{
tid = omp_get_thread_num();
nthreads = omp_get_num_threads();
printf("Hello World from thread = %d out of %d\n", tid, nthreads);
} /* All threads join master thread and disband */
}
omp_private.c - exercises
omp_vectadd.c
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#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[])
{
// Initialize arrays
int size=1000000;
int a[size];
int b[size];
int c[size];
// Time the parallel for-loop
double start,end;
start = omp_get_wtime();
// Fill with a & b with random numbers between 0 and 100
int i;
for(i=0; i<size; i++)
{
a[i]=rand() % 100;
b[i]=rand() % 100;
c[i]=a[i]+b[i];
}
end = omp_get_wtime();
printf("Summed vectors a and b in %g seconds\n", end-start);
}
omp_vectadd.c - exercises
omp_pi.c
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#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main (int argc, char *argv[])
{
//initialize variables
int i;
double pi = 0;
int niter = 100000000;
// Get timing
double start,end;
start=omp_get_wtime();
// Calculate PI using Leibnitz sum
for(i = 0; i < niter; i++)
{
pi = pi + pow(-1, i) * (4 / (2*((double) i)+1));
}
// Stop timing
end=omp_get_wtime();
// Print result
printf("Pi estimate: %.20f, obtained in %f seconds\n", pi, end-start);
}
omp_pi.c - exercises
Solutions
omp_threadnum.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
printf("Hello World from thread = %d\n", omp_get_thread_num());
}
omp_threadnum.c - solutions
omp_hello.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
/* Fork a team of threads */
#pragma omp parallel
{
printf("Hello World from thread = %d\n", omp_get_thread_num());
} /* All threads join master thread and disband */
}
omp_hello.c - solutions
omp_private.c
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#include <omp.h>
#include <stdio.h>
int main (int argc, char *argv[])
{
int tid, nthreads;
/* Fork a team of threads */
#pragma omp parallel private(tid)
{
tid = omp_get_thread_num();
nthreads = omp_get_num_threads();
printf("Hello World from thread = %d out of %d\n", tid, nthreads);
} /* All threads join master thread and disband */
}
omp_private.c - solutions
omp_vectadd.c
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#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[])
{
// Initialize arrays
int size=1000000;
int a[size];
int b[size];
int c[size];
// Time the parallel for-loop
double start,end;
start = omp_get_wtime();
// Fill with a & b with random numbers between 0 and 100
int i;
#pragma omp parallel for
for(i=0; i<size; i++)
{
a[i]=rand() % 100;
b[i]=rand() % 100;
c[i]=a[i]+b[i];
}
end = omp_get_wtime();
printf("Summed vectors a and b in %g seconds\n", end-start);
}
omp_vectadd.c - solutions
omp_pi.c
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#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include "math.h"
int main (int argc, char *argv[])
{
//initialize variables
int i;
double pi = 0;
int niter = 100000000;
// Get timing
double start,end;
start=omp_get_wtime();
// Calculate PI using Leibnitz sum
/* Fork a team of threads */
#pragma omp parallel for reduction(+ : pi)
for(i = 0; i < niter; i++)
{
pi = pi + pow(-1, i) * (4 / (2*((double) i)+1));
} /* Reduction operation is done. All threads join master thread and disband */
// Stop timing
end=omp_get_wtime();
// Print result
printf("Pi estimate: %.20f, obtained in %f seconds\n", pi, end-start);
}
omp_pi.c - solutions
