title: undefined reference to `omp_get_num_procs'
body: <pre><code># include &lt;cstdlib&gt;
  # include &lt;iostream&gt;
  # include &lt;iomanip&gt;
  # include &lt;omp.h&gt;
  
  using namespace std;
  
  int main ( int argc, char *argv[] );
  
  //********************************
  int main ( int argc, char *argv[] )
  //**********************************
  {
    int id;
    double wtime;
  
    cout &lt;&lt; "\n";
    cout &lt;&lt; "HELLO_OPENMP\n";
    cout &lt;&lt; "  C++/OpenMP version\n";
  
    cout &lt;&lt; "\n";
    cout &lt;&lt; "  Number of processors available = " &lt;&lt; omp_get_num_procs ( ) &lt;&lt; "\n";
    cout &lt;&lt; "  Number of threads =              " &lt;&lt; omp_get_max_threads ( ) &lt;&lt; "\n";
  
    wtime = omp_get_wtime ( );
  
  # pragma omp parallel \
    private ( id )
    {
      id = omp_get_thread_num ( );
      cout &lt;&lt; "  This is process " &lt;&lt; id &lt;&lt; "\n";
    }
    wtime = omp_get_wtime ( ) - wtime;
  
    cout &lt;&lt; "\n";
    cout &lt;&lt; "HELLO_OPENMP\n";
    cout &lt;&lt; "  Normal end of execution.\n";
  
    cout &lt;&lt; "\n";
    cout &lt;&lt; "  Elapsed wall clock time = " &lt;&lt; wtime &lt;&lt; "\n";
  
    return 0;
  }
  </code></pre>
  
  <p>Hello,
  I try to run this program:</p>
  
  <p>I run make "filename"       and I had this error:</p>
  
  <p>g++     hello_openmp.cpp   -o hello_openmp
  /tmp/ccz80Tfg.o: In function <code>main':
  hello_openmp.cpp:(.text+0x4d): undefined reference to</code>omp_get_num_procs'
  hello_openmp.cpp:(.text+0x7a): undefined reference to <code>omp_get_max_threads'
  hello_openmp.cpp:(.text+0xa7): undefined reference to</code>omp_get_wtime'
  hello_openmp.cpp:(.text+0xb9): undefined reference to <code>omp_get_thread_num'
  hello_openmp.cpp:(.text+0xea): undefined reference to</code>omp_get_wtime'
  collect2: error: ld returned 1 exit status
  make: *** [hello_openmp] Error 1</p>
  
  <p>Is anyone knows what is the meaning of this error.
  Sorry I am beginner in C++.
  Thank you</p>