Test whether clang++ recognizes openmp

omptest.cpp

#include <omp.h>
#include <stdio.h>
//clang++ -Xpreprocessor -fopenmp -lomp omptest.cpp -o omptest

int main() {
    #pragma omp parallel
    printf("Hello from thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
}