That's the commutative property. It is really nice to have operations that are commutative monoids, where you can re-order the operands, and combine them in any

That's the commutative property. It is really nice to have operations that are commutative monoids, where you can re-order the operands, and combine them in any order, and get the same result. Then if you want to perform that operation (ex. Addition) over a set of operands (ex. Integers), you can do it in parallel, where each process can take any set of intermediate results, and perform the operation on them.