how to refactor nested for loop into smaller for loop assume each of them independent?

[meInvent bbird]

how to refactor nested for loop into smaller for loop assume each of them independent?

because memory is not enough

for ii in range(1,2000):
 for jj in range(1,2000):
  for kk in range(1,2000):
    print run(ii,jj,kk)