Parallel example for computing pi efficiently is actually slow

[rforcen]

first attempt to a more general solution, i'm considering rayon rust module 
parallel implementation which contains parallel iterators, maps, etc.
    
    
    proc par_apply*[T](v:var seq[T], fnc:proc(i:int):T)=
      proc chunk_range(size, i, nth: int): Slice[int] =
        let
          chunk_sz = size div nth
          rfrom = i * chunk_sz
          rto = if (i+1) * chunk_sz > size: size else: (i+1) * chunk_sz
        rfrom..<rto
      
      proc chunk_apply(fnc:proc(i:int):T, i, n : int, v:var seq[T]) =
         for i in chunk_range(size=v.len, i, n):
            v[i] = fnc(i)
      
      let nth = countProcessors()
      
      parallel:
        for i in 0..nth:
          spawn chunk_apply(fnc, i, nth, v)
    
    
    Run