add_range:=proc(lo,hi)

local i;
add(i,i=lo..hi);

end proc:

N:=3*10^8:

 

parallel_add_range:=proc(lo, hi, n)

   local i, step, i_min, d;

d:=hi-lo+1;
step:=floor(d/n);


       Threads:-Task:-Continue( Tasks=[ add_range,
                   seq( [i*step+lo,(i+1)*step], i=0..n-2 ),
                       [ (n-1)*step+lo,hi ] ] );

#       Threads:-Task:-Continue( Task= add_range,1, );

end proc:

start:=time[real]():
  Threads:-Task:-Start(parallel_add_range, 1, N, 2);
time[real]()-start;

Error, invalid input: add_range uses a 1st argument, lo, which is missing