map reduce on as many nodes as you want in 10 lines of Unison code

map-reduce.hs

-- note, syntax here is Unison, just using .hs extension to get some syntax highlighting

-- The mapping function may spawn subcomputations on different nodes, 
-- and the reduction function is done in parallel, building a balanced tree
-- of operations. Computation fails if any step takes longer than timeout
mapreduce : forall a b 
          . Duration -> (a -> Remote b) -> b -> (b -> b -> b) -> Vector a 
         -> Remote b
mapreduce timeout f z op vs = do Remote
  futures := Remote.traverse (f `and-then` Remote.start timeout) vs
  Vector.fold-balanced (Remote.parallel-map2 timeout op) 
                       (Remote.pure z) 
                       futures