VecScatterMsk(const DAD* src, const DAD* dst, const int len,
const DAD* subs [], const int* subsDat [],
const DAD* msk, const int* mskDat)
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.
The pair *msk, mskDat defines a mask array.
Note: the source and destination arguments of VecScatterMsk members are reversed relative to the conventions for most communication schedules. This is to emphasize the symmetry with VecGatherMsk.