parallel_ad<Base>()must be called before any
AD<Base>objects are used in parallel mode. In addition, if this routine is called after one is done using parallel mode, it will free extra memory used to keep track of the multiple
AD<Base>tapes required for parallel execution.
AD<Base>class there is only one tape that records AD of Base operations. This tape is a global variable and hence it cannot be used by multiple threads at the same time. The parallel_setup function informs CppAD of the maximum number of threads that can be active in parallel mode. This routine does extra setup (and teardown) for the particular
CheckSimpleVector< Type, CppAD::vector<Type> >()