Compile[{{Subscript[x, 1],Subscript[t, 1],Subscript[n, 1]},\[Ellipsis]},expr]
assumes that Subscript[x, i] is a rank Subscript[n, i] array of objects, each of a type that matches Subscript[t, i].
assumes that Subscript[x, i] is a rank Subscript[n, i] array of objects, each of a type that matches Subscript[t, i].