std.parallelism and multidimensional arrays

[Stefan Frijters via Digitalmars-d-learn]

I have a code which does a lot of work on 2D/3D arrays, for which 
I use the 2.066 multidimensional slicing syntax through a fork of 
the Unstandard package [1].
Many times the order of operations doesn't matter and I thought I 
would give the parallelism module a try to try and get some easy 
speedups (I also use MPI, but that has some additional overhead).

The way I currently have my foreach loops set up, p is a 
size_t[2], the payload of the array v is double[9] and the array 
is indexed directly with a size_t[2] array and all works fine:

foreach(immutable p, ref v, arr) { double[9] stuff; arr[p] = 
stuff; }

If I naively try

foreach(immutable p, ref v, parallel(arr)) { ... }

I first get errors of the type "Error: foreach: cannot make v 
ref". I do not understand where that particular problem comes 
from, but I can possibly live without the ref, so I went for

foreach(immutable p, v, parallel(arr)) { ... }

Which gets me "Error: no [] operator overload for type 
(complicated templated type of some wrapper struct I have for 
arr)". I'm guessing it doesn't like that there is no such thing 
as a simple one-dimensional slicing operation for a 
multidimensional array?
Should I define an opSlice function that takes the usual two 
size_t arguments for the upper and lower bounds and doesn't 
require a dimension template argument and somehow map this to my 
underlying two-dimensional array? Will it need an opIndex 
function that takes only takes a single size_t as well?
Or is this just taking the simple parallel(...) too far and 
should I try to put something together myself using lower-level 
constructs?

Any hints would be appreciated!

[1] http://code.dlang.org/packages/unstandard