parallel.h

#pragma once

#ifndef _OPENMP
#ifndef SINGLE_THREAD
#define SINGLE_THREAD
#endif
#endif

#ifndef SINGLE_THREAD
#include <omp.h>
#endif

extern size_t threshold;

namespace parallel {
extern size_t lastThreads;
inline size_t get_thread_num()
{
#ifdef SINGLE_THREAD
  return 0;
#else
  return omp_get_thread_num();
#endif
}

inline size_t get_thread_num(size_t threads) {
  return threads > 1 ? get_thread_num() : 0;
}

inline size_t get_max_threads()
{
#ifdef SINGLE_THREAD
  return 1;
#else
  return omp_get_max_threads();
#endif
}
}

#ifndef SINGLE_THREAD
#define PARALLEL(code)                                  \
  if(threads > 1) {                                     \
    _Pragma("omp parallel for num_threads(threads)")    \
      code                                              \
      } else {code}
#else
#define PARALLEL(code) {code}
#endif

#ifndef SINGLE_THREAD
#define OMPIF(condition,directive,code)         \
  if(threads > 1 && condition) {                \
    _Pragma(directive)                          \
      code                                      \
      } else {code}
#else
#define OMPIF(condition,directive,code) {code}
#endif

#define PARALLELIF(condition,code)                              \
  OMPIF(condition,"omp parallel for num_threads(threads)",code)

namespace parallel {

void Threshold(size_t threads);

}