Alternatively it involves actually mathematically proving that the function is used correctly, which is rather hard in sequential programming languages, and nig

Alternatively it involves actually mathematically proving that the function is used correctly, which is rather hard in sequential programming languages, and nigh impossible in parallel. Just proving the alleged "sync" works is a nightmare involving some proof or assumptions on underlying hardware. Exhaustive testing of parallel behaviors is near impossible too. Removing logic can only go as far as the essentials that are required for solving the problem.