code: def mpf_sum(xs, prec=0, rnd=round_fast, absolute=False):
      """
      Sum a list of mpf values efficiently and accurately
      (typically no temporary roundoff occurs). If prec=0,
      the final result will not be rounded either.
  
      There may be roundoff error or cancellation if extremely
      large exponent differences occur.
  
      With absolute=True, sums the absolute values.
      """
      man = 0
      exp = 0
      max_extra_prec = prec * 2 or 1000000  # XXX
      special = None
      for x in xs:
          xsign, xman, xexp, xbc = x
          if xman:
              if xsign and not absolute:
                  xman = -xman
              delta = xexp - exp
              if xexp >= exp:
                  # x much larger than existing sum?
                  # first: quick test
                  if (delta > max_extra_prec) and (
                      (not man)
                      or delta - bitcount(abs(man)) > max_extra_prec
                  ):
                      man = xman
                      exp = xexp
                  else:
                      man += xman << delta
              else:
                  delta = -delta
                  # x much smaller than existing sum?
                  if delta - xbc > max_extra_prec:
                      if not man:
                          man, exp = xman, xexp
                  else:
                      man = (man << delta) + xman
                      exp = xexp
          elif xexp:
              if absolute:
                  x = mpf_abs(x)
              special = mpf_add(special or fzero, x, 1)
      # Will be inf or nan
      if special:
          return special
      return from_man_exp(man, exp, prec, rnd)
  
imports: import math
  from bisect import bisect
  import sys
  from .backend import MPZ, MPZ_TYPE, MPZ_ZERO, MPZ_ONE, MPZ_TWO, MPZ_FIVE, BACKEND, STRICT, HASH_MODULUS, HASH_BITS, gmpy, sage, sage_utils
  from .libintmath import giant_steps, trailtable, bctable, lshift, rshift, bitcount, trailing, sqrt_fixed, numeral, isqrt, isqrt_fast, sqrtrem, bin_to_radix
label_desc: Use image node_id 41 for calling a global function with example usage: mpf_sum(xs, prec, rnd, absolute) and returns: from_man_exp, special