c++ - How to perform basic operations with std::atomic when the type is not Integral? -

to precise, need increase double double , want thread safe. don't want use mutex since execution speed dramatically decrease.

as rule, c++ standard library tries provide operations can implemented efficiently. std::atomic, means operations can performed lock-free in instruction or 2 on "common" architectures. "common" architectures have atomic fetch-and-add instructions integers, not floating point types.

if want implement math operations atomic floating point types, you'll have cas (compare , swap) loop (live @ coliru):

std::atomic<double> foo{0};  void add_to_foo(double bar) {   auto current = foo.load();   while (!foo.compare_exchange_weak(current, current + bar))     ; }