Revert "fix typo in [71e1b8c6]"

This reverts commit 2110818f9ee1c89aca3e6d7ad6c19c9d87b0dacc.
Revert "change code to avoid multiple different types in initialization part of the loops"

This reverts commit 71e1b8c646b5c66815e4ddef2bee7522d89f369b.
Revert "change type of counters to size_t to silence warnings about sign mismatch"

This reverts commit 946c1667c24bd9748c05c11a4a4199f27ebb7b16.
Tidy up unit test.
Add sample benchmark of SSE vs C