Arch Dispatching

xsimd provides a generic way to dispatch a function call based on the architecture the code was compiled for and the architectures available at runtime. The :cpp:func::xsimd::dispatch function takes a functor whose call operator takes an architecture parameter as first operand, followed by any number of arguments Args... and turn it into a dispatching functor that takes Args... as arguments.

template<class F, class ArchList = supported_architectures>
inline detail::dispatcher<F, ArchList> xsimd::dispatch(F &&f)

Following code showcases a usage of the :cpp:func::xsimd::dispatch function:

// functor with a call method that depends on `Arch`
struct sum {
  template<class Arch, class T>
  T operator()(Arch, T const* data, unsigned size)
  {
    using batch = xsimd::batch<T, Arch>;
    batch acc(static_cast<T>(0));
    const unsigned n = size / batch::size * batch::size;
    for(unsigned i = 0; i != n; i += batch::size)
        acc += batch::load_unaligned(data + i);
    T star_acc = xsimd::hadd(acc);
    for(unsigned i = n; i < size; ++i)
      star_acc += data[i];
    return star_acc;
  }
};

// Create the dispatching function.
auto dispatched = xsimd::dispatch(sum{});

// Call the appropriate implementation based on runtime information.
float res = dispatched(data, 17);