all the elements. Parallel_reduce with a grain_size of 2500 will then allocate
an intermediate result tensor with 4 elements. Then it will execute the function
"f" you provide and pass the beginning and end index of these chunks, so
-0-24999, 2500-4999, etc. and the combination identity. It will then write out
+0-2499, 2500-4999, etc. and the combination identity. It will then write out
the result from each of these chunks into the intermediate result tensor. After
that it'll reduce the partial results from each chunk into a single number using
the combination function sf and the identity ident. For a total summation this