error in compiling using both gsl and openmp

[robjons21]

Hello All,
I am trying to write a program that uses both GSL and OpenMP.

I have no problem using GSL and OpenMP separately, but I'm having issues using both. For instance, I can compile the GSL program By typing

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$gcc -c Bessel.c
$gcc Bessel.o -lgsl -lgslcblas -lm
$./a.out

and it works.

I was also able to compile the program that uses OpenMP In this case I typed

Code: Select all

$gcc -fopenmp test_omp.c
$./a.out

And I got what I wanted (all 4 threads I have were used).

However, when I simply write a program that combines the two codes

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#include <stdio.h>
#include <gsl/gsl_sf_bessel.h>
#include <omp.h>

int
main (void)
{
   double x = 5.0;
   double y = gsl_sf_bessel_J0 (x);
   printf ("J0(%g) = %.18e\n", x, y);`


int dimension = 4;
int i = 0;
int j = 0;
#pragma omp parallel private(i, j)
for (i =0; i < dimension; i++)
    for (j = 0; j < dimension; j++)
        printf("i=%d, jjj=%d, thread = %d\n", i, j, omp_get_thread_num());

return 0;

}`


Then I try to compile to typing

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$gcc -c Bessel_omp_test.c
$gcc Bessel_omp_test.o -fopenmp -lgsl -lgslcblas -lm
$./a.out

The GSL part works (The Bessel function is computed), but only one thread is used for the OpenMP part. I'm not sure what's wrong here...
If any body can help me here!!!
Thanks

[MarkB]

I think you need to compile and link with the -fopenmp flag:

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$gcc -c -fopenmp Bessel_omp_test.c
$gcc Bessel_omp_test.o -fopenmp -lgsl -lgslcblas -lm
$./a.out