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///
/// @file OmpLock.hpp
/// @brief The OmpLock and LockGuard classes are RAII-style
/// wrappers for OpenMP locks.
///
/// Copyright (C) 2022 Kim Walisch, <kim.walisch@gmail.com>
///
/// This file is distributed under the BSD License. See the COPYING
/// file in the top level directory.
///
#ifndef OMPLOCK_HPP
#define OMPLOCK_HPP
#include <macros.hpp>
#include <primecount-config.hpp>
#if defined(_OPENMP)
#include <omp.h>
#else
// If OpenMP is disabled we define the functions used by
// the OmpLock and LockGuard classes as no-op.
namespace {
using omp_lock_t = int;
inline void omp_init_lock(omp_lock_t*) { }
inline void omp_destroy_lock(omp_lock_t*) { }
inline void omp_set_lock(omp_lock_t*) { }
inline void omp_unset_lock(omp_lock_t*) { }
} // namespace
#endif
namespace primecount {
struct OmpLock
{
void init(int threads)
{
ASSERT(!is_initialized());
ASSERT(threads > 0);
threads_ = threads;
if (threads_ > 1)
omp_init_lock(&lock_);
}
~OmpLock()
{
if (threads_ > 1)
omp_destroy_lock(&lock_);
}
bool is_initialized() const
{
return threads_ > 0;
}
// 0 = uninitialized lock
unsigned threads_ = 0;
// Use padding to avoid CPU false sharing
MAYBE_UNUSED char pad1[MAX_CACHE_LINE_SIZE];
omp_lock_t lock_;
MAYBE_UNUSED char pad2[MAX_CACHE_LINE_SIZE];
};
class LockGuard
{
public:
LockGuard(OmpLock& lock)
{
ASSERT(lock.is_initialized());
if (lock.threads_ > 1)
{
lock_ = &lock.lock_;
omp_set_lock(lock_);
}
}
~LockGuard()
{
if (lock_)
omp_unset_lock(lock_);
}
private:
omp_lock_t* lock_ = nullptr;
};
} // namespace
#endif
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