[OpenMP] Solution 3 : AXPY Operation

This material is part of the course Practical Introduction to Parallel Programming and meant for educational purposes only.

Task

Write a parallel program that computes

\begin{equation*} \mathbf{y}:=\alpha\mathbf{x}+\mathbf{y} \end{equation*}

for two vectors \(\mathbf{x},\mathbf{y}\in\mathbb{R}^N\) and a scalar coefficient \(\alpha\in\mathbb{R}\).

Test your program for different scheduling strategies and chunk sizes, and different values for \(N\).

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Question 1: AXPY Operation

#include <stdio.h>

#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_num_threads() 1
#define omp_get_max_threads() 1
#define omp_get_thread_num()  0
#endif

int main ( int argc, char** argv )
{
    const int n=1000;
    const int alpha=2;
    int x[n],y[n];

    double t0 = omp_get_wtime();

#pragma omp parallel default(none) shared(x,y)
    {
        /* Initialization */
#pragma omp for schedule(static) nowait
        for (int i=0; i<n; i++)
            {
                x[i] = i; y[i]= i ;
            }

        /* Parallel axpy */
#pragma omp for schedule(static)
        for (int i=0; i<n; i++)
            {
                y[i] += alpha*x[i];
            }
    }

    double t1 = omp_get_wtime();

    if (n<10)
    {
        printf("AXPY (in %g seconds):\n", t1-t0);
        for (int i=0; i<n; i++)
        {
            printf("%d ", y[i]);
        }
    }
    else
        printf("AXPY (in %g seconds):\nSet n<10 to produce output\n", t1-t0);

    return 0;
}

Question 2: OpenMP environment variables

Specify the OpenMP environment variables that should be used for running your program (export OMP_NUM_THREADS=1 ...). Use semicolons to separate multiple variables

Question 3: Command Line Argument

Specify the command line arguments that should be passed to your program when it is run. Arguments must be given in quotes and separated by commas. Leave this filed empty if you do not want to specify command line arguments.

Example: "1","int","arg=2" is interpreted as three arguments 1, int, and arg=2.

Author(s)	Erik-Jan Lingen, Matthias Möller
Deadline	No deadline
Submission limit	No limitation

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