message: Core: Added single field reduce also to sequential backend
diff: @@ -10,6 +10,17 @@ namespace Backend
  {
  namespace seq
  {
  + template<typename A, typename F>
  + scalar reduce(const field<A> & vf1, const F f)
  + {
  + scalar res=0;
  + #pragma omp parallel for reduction(+:res)
  + for(unsigned int idx = 0; idx < vf1.size(); ++idx)
  + {
  + res += f(vf1[idx]);
  + }
  + return res;
  + }
  // result = sum_i f( vf1[i], vf2[i] )
  template<typename A, typename B, typename F>
  