VecGather(const DAD* dst, const DAD* src, const int len,
const DAD* subs [], const int* subsDat [])
The source array is described by the DAD *src and the
destination array is described by the DAD *dst.
len specifies the size of each array element, in bytes.
The source and destination arrays have the same rank, R.
The vectors subs and subsDat have extent R.
If subs [r] is non-null,
the pair *subs [r], subsDat [r] defines
the rth subscript array.