void copymask(OLattice<T2>& dest, const OLattice<T1>& mask, const OLattice<T2>& s1)
void copymask(OSubLattice<T2> d, const OLattice<T1>& mask, const OLattice<T2>& s1)
void copymask(OLattice<T2>& dest, const OLattice<T1>& mask, const OLattice<T2>& s1) {  for(int i=0; i < Layout::subgridVol(); ++i)     copymask(dest.elem(i), mask.elem(i), s1.elem(i));}