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geant4/examples/extended/parallel/ThreadsafeScorers/include/G4atomic.hh
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2018-12-07 15:15:39 +01:00

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//
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/// \file parallel/ThreadsafeScorers/include/G4atomic.hh
/// \brief Definition of the G4atomic class
//
//
//
//
/// This is an friendly implementation of the STL atomic class.
/// This class has the same interface as the STL atomic but can be used
/// in an extremely similar fashion to plain old data (POD) types.
/// In other words, the copy constructor and assignment operators are
/// defined, and a load() does not need to be called to get the POD
/// value.
///
/// IMPORTANT: Care must be taken when using this class as a RHS term.
/// The best use case scenario for this class is as a LHS term that is
/// only used as a RHS term outside of the multithreaded operations on it.
///
/// FOR EXAMPLE:
/// Proper use:
/// Goal: sum energy deposited in run
/// Impl: Is a member variable of derived
/// G4VUserActionInitialization (of which there will
/// always be just one instance). Accumulate
/// thread-local energy deposit into EventAction,
/// add to ActionInit at end of event, print sum
/// on master EndOfRunAction
/// Why: the sum is only a LHS term
/// Improper use:
/// Goal: compute error during event processing
/// Impl: sum += x; sum_sq += x*x; counts++;
/// error = sqrt(sum_sq/(sum*sum) - 1/counts;
/// (where sum, sum_sq, counts are G4atomics)
/// Why: This will work but error can/will be wrong when
/// sum, sum_sq, and counts are updated by another thread
/// while error is being calculated, i.e. they are used as
/// RHS terms
//
//
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#ifndef G4atomic_hh_
#define G4atomic_hh_
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#ifdef G4MULTITHREADED
#include "G4atomic_defines.hh"
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template<typename _Tp>
class G4atomic
{
public:
typedef typename std::atomic<_Tp> base_type;
typedef _Tp value_type;
private:
using mem_ord = std::memory_order;
public:
// constructors
explicit
G4atomic(mem_ord mo = std::memory_order_acq_rel) : fMemOrder(mo)
{ atomics::set(&fvalue, value_type()); }
explicit
G4atomic(const value_type& _init,
mem_ord mo = std::memory_order_acq_rel) : fMemOrder(mo)
{ atomics::set(&fvalue, _init); }
// copy-constructor from pure C++11 atomic
explicit
G4atomic(const base_type& rhs,
mem_ord mo = std::memory_order_acq_rel) : fMemOrder(mo)
{ atomics::set(&fvalue, rhs); }
// copy-constructor
explicit
G4atomic(const G4atomic& rhs) : fMemOrder(rhs.fMemOrder)
{ atomics::set(&fvalue, rhs.base()); }
// assignment operators
G4atomic& operator=(const G4atomic& rhs)
{
if(this != &rhs)
atomics::set(&fvalue, rhs.fvalue);
return *this;
}
G4atomic& operator=(const value_type& rhs)
{
atomics::set(&fvalue, rhs);
return *this;
}
G4atomic& operator=(const base_type& rhs)
{
atomics::set(&fvalue, rhs);
return *this;
}
// destructor
~G4atomic() { fvalue.~base_type(); }
// base version
base_type& base() { return fvalue; }
const base_type& base() const { return fvalue; }
base_type& base() volatile { return fvalue; }
const base_type& base() const volatile { return fvalue; }
// check if atomic is lock-free
bool is_lock_free() const { return fvalue.is_lock_free(); }
bool is_lock_free() const volatile { return fvalue.is_lock_free(); }
// store functions
void store(_Tp _desired, mem_ord mo = std::memory_order_seq_cst)
{ atomics::set(fvalue, _desired, mo); }
void store(_Tp _desired, mem_ord mo = std::memory_order_seq_cst) volatile
{ atomics::set(fvalue, _desired, mo); }
// load functions
_Tp load(mem_ord mo = std::memory_order_seq_cst) const
{ return atomics::get(fvalue, mo); }
_Tp load(mem_ord mo = std::memory_order_seq_cst) const volatile
{ return atomics::get(fvalue, mo); }
// implicit conversion functions
operator _Tp() const { return this->load(); }
operator _Tp() const volatile { return this->load(); }
operator base_type&() const { return fvalue; }
// compare-and-swap functions
bool compare_exchange_weak(_Tp& _expected, _Tp _desired,
mem_ord _success, mem_ord _failure)
{ return fvalue.compare_exchange_weak(_expected, _desired,
_success, _failure); }
bool compare_exchange_weak(_Tp& _expected, _Tp _desired,
mem_ord _success, mem_ord _failure) volatile
{ return fvalue.compare_exchange_weak(_expected, _desired,
_success, _failure); }
bool compare_exchange_weak(_Tp& _expected, _Tp _desired, mem_ord _order)
{ return fvalue.compare_exchange_weak(_expected, _desired, _order); }
bool compare_exchange_weak(_Tp& _expected, _Tp _desired,
mem_ord _order) volatile
{ return fvalue.compare_exchange_weak(_expected, _desired, _order); }
bool compare_exchange_strong(_Tp& _expected, _Tp _desired,
mem_ord _success, mem_ord _failure)
{ return fvalue.compare_exchange_weak(_expected, _desired,
_success, _failure); }
bool compare_exchange_strong(_Tp& _expected, _Tp _desired,
mem_ord _success, mem_ord _failure) volatile
{ return fvalue.compare_exchange_weak(_expected, _desired,
_success, _failure); }
bool compare_exchange_strong(_Tp& _expected, _Tp _desired, mem_ord _order)
{ return fvalue.compare_exchange_weak(_expected, _desired, _order); }
bool compare_exchange_strong(_Tp& _expected, _Tp _desired,
mem_ord _order) volatile
{ return fvalue.compare_exchange_weak(_expected, _desired, _order); }
// value_type operators
G4atomic& operator+=(const value_type& rhs)
{ atomics::increment(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator-=(const value_type& rhs)
{ atomics::decrement(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator*=(const value_type& rhs)
{ atomics::multiply(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator/=(const value_type& rhs)
{ atomics::divide(&fvalue, rhs, fMemOrder); return *this; }
// atomic operators
G4atomic& operator+=(const G4atomic& rhs)
{ atomics::increment(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator-=(const G4atomic& rhs)
{ atomics::decrement(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator*=(const G4atomic& rhs)
{ atomics::multiply(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator/=(const G4atomic& rhs)
{ atomics::divide(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator+=(const G4atomic& rhs) volatile
{ atomics::increment(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator-=(const G4atomic& rhs) volatile
{ atomics::decrement(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator*=(const G4atomic& rhs) volatile
{ atomics::multiply(&fvalue, rhs.fvalue); return *this; }
G4atomic& operator/=(const G4atomic& rhs) volatile
{ atomics::divide(&fvalue, rhs.fvalue); return *this; }
// STL atomic operators
G4atomic& operator+=(const std::atomic<_Tp>& rhs)
{ atomics::increment(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator-=(const std::atomic<_Tp>& rhs)
{ atomics::decrement(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator*=(const std::atomic<_Tp>& rhs)
{ atomics::multiply(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator/=(const std::atomic<_Tp>& rhs)
{ atomics::divide(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator+=(const std::atomic<_Tp>& rhs) volatile
{ atomics::increment(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator-=(const std::atomic<_Tp>& rhs) volatile
{ atomics::decrement(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator*=(const std::atomic<_Tp>& rhs) volatile
{ atomics::multiply(&fvalue, rhs, fMemOrder); return *this; }
G4atomic& operator/=(const std::atomic<_Tp>& rhs) volatile
{ atomics::divide(&fvalue, rhs, fMemOrder); return *this; }
// increment operators
value_type operator++() { value_type _tmp = ++fvalue; return _tmp; }
value_type operator++(int)
{ value_type _tmp = fvalue++; return _tmp; }
value_type operator--() { value_type _tmp = --fvalue; return _tmp; }
value_type operator--(int)
{ value_type _tmp = fvalue--; return _tmp; }
protected:
base_type fvalue;
mem_ord fMemOrder;
};
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#else // ! G4MULTITHREADED
template <typename _Tp> using G4atomic = _Tp;
#endif // G4MULTITHREADED
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#endif // G4atomic_hh_