code: def _select_vs(v, p):
      # This one is is about 30 times faster than
      # the generic algorithm it is replacing.
      
  
      if v >= 120.:
          return 60, 120, inf
      elif v >= 60.:
          return 40, 60, 120
      elif v >= 40.:
          return 30, 40, 60
      elif v >= 30.:
          return 24, 30, 40
      elif v >= 24.:
          return 20, 24, 30
      elif v >= 19.5:
          return 19, 20, 24
  
      if p >= .9:
          if v < 2.5:
              return 1, 2, 3
      else:
          if v < 3.5:
              return 2, 3, 4
  
      vi = int(round(v))
      return vi - 1, vi, vi + 1
docs: returns the points to use for interpolating v