tweak form of 'reduce()'

Author: kevinushey

inst/include/RcppParallel/simd/map_reduce.h

@@ -34,8 +34,8 @@ U simdMapReduce(const T* it, const T* end, U init, MapReducer mapper)
    for (; it != aligned_end; it += N)
       mapper.map(boost::simd::aligned_load<vT>(it), &buffer);
 
-   // Reduce our buffer
-   mapper.reduce(buffer, &init);
+   // Reduce our buffer, and join it with the initial value
+   mapper.map(mapper.reduce(buffer), &init);
 
    // Leftover unaligned region
    for (; it != end; ++it)