Error "undefined reference to omp_get_wtime"

Question

I cannot find which library to link in GCC (4.8) under Windows (Vista). I tried the -fopenmp -llibgomp -lgomp compiler directives, but none works.

I already have GCC with POSIX (so std::thread is working if enabling C++11). The problem seems that searching for the right library does not provide useful results (even searching in GCC/MinGW documentation).

So basically I can't get this answer working (the answer claimed to work on most compilers, but it doesn’t provide additional information on how to get it working, so I can't verify if it is really working or not).

It would be nice to provide now additional information to get it working on most systems...

Answer 1

MinGW-w64 based on GCC 4.8.1 from here has no problems so far.

Example: C

---

main.c

#include <omp.h>
#include <stdio.h>

int
main() {
  double x = omp_get_wtime();

  printf("%f\n", x);
}

Build:

gcc main.c -lgomp -o test.exe

Result:

1381572544.299000

Example: C++

---

main.cpp

#include <iostream>
#include <omp.h>

using std::cout;
using std::endl;

int
main() {
  double x = omp_get_wtime();

  cout << x << endl;
}

Build:

g++ main.cpp -lgomp -o test.exe

Result:

1.38158e+009

Conclusion

---

Probably something is wrong with your MinGW distribution. Otherwise I don't see any reason for it not to work. Try the above one and see how it goes.