C++ MPFR_INT_CEIL_LOG2函数代码示例

int
mpfr_const_euler_internal (mpfr_t x, mpfr_rnd_t rnd)
{
  mpfr_prec_t prec = MPFR_PREC(x), m, log2m;
  mpfr_t y, z;
  unsigned long n;
  int inexact;
  MPFR_ZIV_DECL (loop);

  log2m = MPFR_INT_CEIL_LOG2 (prec);
  m = prec + 2 * log2m + 23;

  mpfr_init2 (y, m);
  mpfr_init2 (z, m);

  MPFR_ZIV_INIT (loop, m);
  for (;;)
    {
      mpfr_exp_t exp_S, err;
      /* since prec >= 1, we have m >= 24 here, which ensures n >= 9 below */
      n = 1 + (unsigned long) ((double) m * LOG2 / 2.0);
      MPFR_ASSERTD (n >= 9);
      mpfr_const_euler_S2 (y, n); /* error <= 3 ulps */
      exp_S = MPFR_EXP(y);
      mpfr_set_ui (z, n, MPFR_RNDN);
      mpfr_log (z, z, MPFR_RNDD); /* error <= 1 ulp */
      mpfr_sub (y, y, z, MPFR_RNDN); /* S'(n) - log(n) */
      /* the error is less than 1/2 + 3*2^(exp_S-EXP(y)) + 2^(EXP(z)-EXP(y))
         <= 1/2 + 2^(exp_S+2-EXP(y)) + 2^(EXP(z)-EXP(y))
         <= 1/2 + 2^(1+MAX(exp_S+2,EXP(z))-EXP(y)) */
      err = 1 + MAX(exp_S + 2, MPFR_EXP(z)) - MPFR_EXP(y);
      err = (err >= -1) ? err + 1 : 0; /* error <= 2^err ulp(y) */
      exp_S = MPFR_EXP(y);
      mpfr_const_euler_R (z, n); /* err <= ulp(1/2) = 2^(-m) */
      mpfr_sub (y, y, z, MPFR_RNDN);
      /* err <= 1/2 ulp(y) + 2^(-m) + 2^(err + exp_S - EXP(y)) ulp(y).
         Since the result is between 0.5 and 1, ulp(y) = 2^(-m).
         So we get 3/2*ulp(y) + 2^(err + exp_S - EXP(y)) ulp(y).
         3/2 + 2^e <= 2^(e+1) for e>=1, and <= 2^2 otherwise */
      err = err + exp_S - MPFR_EXP(y);
      err = (err >= 1) ? err + 1 : 2;
      if (MPFR_LIKELY (MPFR_CAN_ROUND (y, m - err, prec, rnd)))
        break;
      MPFR_ZIV_NEXT (loop, m);
      mpfr_set_prec (y, m);
      mpfr_set_prec (z, m);
    }
  MPFR_ZIV_FREE (loop);

  inexact = mpfr_set (x, y, rnd);

  mpfr_clear (y);
  mpfr_clear (z);

  return inexact; /* always inexact */
}

static void
test_int_ceil_log2 (void)
{
  int i;
  int val[16] = { 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };

  for (i = 1; i < 17; i++)
    {
      if (MPFR_INT_CEIL_LOG2 (i) != val[i-1])
        {
          printf ("Error 1 in test_int_ceil_log2 for i = %d\n", i);
          exit (1);
        }
      if (MPFR_INT_CEIL_LOG2 (i) != __gmpfr_int_ceil_log2 (i))
        {
          printf ("Error 2 in test_int_ceil_log2 for i = %d\n", i);
          exit (1);
        }
    }
}

//.........这里部分代码省略.........
        {
          mpfr_sub (tmp, tmp, tmp2, MPFR_RNDZ); /* low bnd on |sin(Pi*(2-x))| */
          mpfr_ui_div (tmp, 12, tmp, MPFR_RNDU); /* upper bound */
          mpfr_log2 (tmp, tmp, MPFR_RNDU);
          mpfr_add (xp, tmp, xp, MPFR_RNDU);
          /* The assert below checks that expo.saved_emin - 2 always
             fits in a long. FIXME if we want to allow mpfr_exp_t to
             be a long long, for instance. */
          MPFR_ASSERTN (MPFR_EMIN_MIN - 2 >= LONG_MIN);
          underflow = mpfr_cmp_si (xp, expo.saved_emin - 2) <= 0;
        }

      mpfr_clear (xp);
      mpfr_clear (tmp);
      mpfr_clear (tmp2);
      if (underflow) /* the sign is the opposite of that of sin(Pi*(2-x)) */
        {
          MPFR_SAVE_EXPO_FREE (expo);
          return mpfr_underflow (gamma, (rnd_mode == MPFR_RNDN) ? MPFR_RNDZ : rnd_mode, -sgn);
        }
    }

  realprec = MPFR_PREC (gamma);
  /* we want both 1-x and 2-x to be exact */
  {
    mpfr_prec_t w;
    w = mpfr_gamma_1_minus_x_exact (x);
    if (realprec < w)
      realprec = w;
    w = mpfr_gamma_2_minus_x_exact (x);
    if (realprec < w)
      realprec = w;
  }
  realprec = realprec + MPFR_INT_CEIL_LOG2 (realprec) + 20;
  MPFR_ASSERTD(realprec >= 5);

  MPFR_GROUP_INIT_4 (group, realprec + MPFR_INT_CEIL_LOG2 (realprec) + 20,
                     xp, tmp, tmp2, GammaTrial);
  mpz_init (fact);
  MPFR_ZIV_INIT (loop, realprec);
  for (;;)
    {
      mpfr_exp_t err_g;
      int ck;
      MPFR_GROUP_REPREC_4 (group, realprec, xp, tmp, tmp2, GammaTrial);

      /* reflection formula: gamma(x) = Pi*(x-1)/sin(Pi*(2-x))/gamma(2-x) */

      ck = mpfr_ui_sub (xp, 2, x, MPFR_RNDN); /* 2-x, exact */
      MPFR_ASSERTD(ck == 0);  (void) ck; /* use ck to avoid a warning */
      mpfr_gamma (tmp, xp, MPFR_RNDN);   /* gamma(2-x), error (1+u) */
      mpfr_const_pi (tmp2, MPFR_RNDN);   /* Pi, error (1+u) */
      mpfr_mul (GammaTrial, tmp2, xp, MPFR_RNDN); /* Pi*(2-x), error (1+u)^2 */
      err_g = MPFR_GET_EXP(GammaTrial);
      mpfr_sin (GammaTrial, GammaTrial, MPFR_RNDN); /* sin(Pi*(2-x)) */
      /* If tmp is +Inf, we compute exp(lngamma(x)). */
      if (mpfr_inf_p (tmp))
        {
          inex = mpfr_explgamma (gamma, x, &expo, tmp, tmp2, rnd_mode);
          if (inex)
            goto end;
          else
            goto ziv_next;
        }
      err_g = err_g + 1 - MPFR_GET_EXP(GammaTrial);
      /* let g0 the true value of Pi*(2-x), g the computed value.

/* agm(x,y) is between x and y, so we don't need to save exponent range */
int
mpfr_agm (mpfr_ptr r, mpfr_srcptr op2, mpfr_srcptr op1, mp_rnd_t rnd_mode)
{
  int compare, inexact;
  mp_size_t s;
  mp_prec_t p, q;
  mp_limb_t *up, *vp, *tmpp;
  mpfr_t u, v, tmp;
  unsigned long n; /* number of iterations */
  unsigned long err = 0;
  MPFR_ZIV_DECL (loop);
  MPFR_TMP_DECL(marker);

  MPFR_LOG_FUNC (("op2[%#R]=%R op1[%#R]=%R rnd=%d", op2,op2,op1,op1,rnd_mode),
                 ("r[%#R]=%R inexact=%d", r, r, inexact));

  /* Deal with special values */
  if (MPFR_ARE_SINGULAR (op1, op2))
    {
      /* If a or b is NaN, the result is NaN */
      if (MPFR_IS_NAN(op1) || MPFR_IS_NAN(op2))
        {
          MPFR_SET_NAN(r);
          MPFR_RET_NAN;
        }
      /* now one of a or b is Inf or 0 */
      /* If a and b is +Inf, the result is +Inf.
         Otherwise if a or b is -Inf or 0, the result is NaN */
      else if (MPFR_IS_INF(op1) || MPFR_IS_INF(op2))
        {
          if (MPFR_IS_STRICTPOS(op1) && MPFR_IS_STRICTPOS(op2))
            {
              MPFR_SET_INF(r);
              MPFR_SET_SAME_SIGN(r, op1);
              MPFR_RET(0); /* exact */
            }
          else
            {
              MPFR_SET_NAN(r);
              MPFR_RET_NAN;
            }
        }
      else /* a and b are neither NaN nor Inf, and one is zero */
        {  /* If a or b is 0, the result is +0 since a sqrt is positive */
          MPFR_ASSERTD (MPFR_IS_ZERO (op1) || MPFR_IS_ZERO (op2));
          MPFR_SET_POS (r);
          MPFR_SET_ZERO (r);
          MPFR_RET (0); /* exact */
        }
    }
  MPFR_CLEAR_FLAGS (r);

  /* If a or b is negative (excluding -Infinity), the result is NaN */
  if (MPFR_UNLIKELY(MPFR_IS_NEG(op1) || MPFR_IS_NEG(op2)))
    {
      MPFR_SET_NAN(r);
      MPFR_RET_NAN;
    }

  /* Precision of the following calculus */
  q = MPFR_PREC(r);
  p = q + MPFR_INT_CEIL_LOG2(q) + 15;
  MPFR_ASSERTD (p >= 7); /* see algorithms.tex */
  s = (p - 1) / BITS_PER_MP_LIMB + 1;

  /* b (op2) and a (op1) are the 2 operands but we want b >= a */
  compare = mpfr_cmp (op1, op2);
  if (MPFR_UNLIKELY( compare == 0 ))
    {
      mpfr_set (r, op1, rnd_mode);
      MPFR_RET (0); /* exact */
    }
  else if (compare > 0)
    {
      mpfr_srcptr t = op1;
      op1 = op2;
      op2 = t;
    }
  /* Now b(=op2) >= a (=op1) */

  MPFR_TMP_MARK(marker);

  /* Main loop */
  MPFR_ZIV_INIT (loop, p);
  for (;;)
    {
      mp_prec_t eq;

      /* Init temporary vars */
      MPFR_TMP_INIT (up, u, p, s);
      MPFR_TMP_INIT (vp, v, p, s);
      MPFR_TMP_INIT (tmpp, tmp, p, s);

      /* Calculus of un and vn */
      mpfr_mul (u, op1, op2, GMP_RNDN); /* Faster since PREC(op) < PREC(u) */
      mpfr_sqrt (u, u, GMP_RNDN);
      mpfr_add (v, op1, op2, GMP_RNDN); /* add with !=prec is still good*/
      mpfr_div_2ui (v, v, 1, GMP_RNDN);
      n = 1;
//.........这里部分代码省略.........

int
mpfr_mul_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mpfr_rnd_t rnd_mode)
{
  mp_limb_t *yp;
  mp_size_t xn;
  int cnt, inexact;
  MPFR_TMP_DECL (marker);

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    {
      if (MPFR_IS_NAN (x))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else if (MPFR_IS_INF (x))
        {
          if (u != 0)
            {
              MPFR_SET_INF (y);
              MPFR_SET_SAME_SIGN (y, x);
              MPFR_RET (0); /* infinity is exact */
            }
          else /* 0 * infinity */
            {
              MPFR_SET_NAN (y);
              MPFR_RET_NAN;
            }
        }
      else /* x is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (x));
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0); /* zero is exact */
        }
    }
  else if (MPFR_UNLIKELY (u <= 1))
    {
      if (u < 1)
        {
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0); /* zero is exact */
        }
      else
        return mpfr_set (y, x, rnd_mode);
    }
  else if (MPFR_UNLIKELY (IS_POW2 (u)))
    return mpfr_mul_2si (y, x, MPFR_INT_CEIL_LOG2 (u), rnd_mode);

  yp = MPFR_MANT (y);
  xn = MPFR_LIMB_SIZE (x);

  MPFR_ASSERTD (xn < MP_SIZE_T_MAX);
  MPFR_TMP_MARK(marker);
  yp = MPFR_TMP_LIMBS_ALLOC (xn + 1);

  MPFR_ASSERTN (u == (mp_limb_t) u);
  yp[xn] = mpn_mul_1 (yp, MPFR_MANT (x), xn, u);

  /* x * u is stored in yp[xn], ..., yp[0] */

  /* since the case u=1 was treated above, we have u >= 2, thus
     yp[xn] >= 1 since x was msb-normalized */
  MPFR_ASSERTD (yp[xn] != 0);
  if (MPFR_LIKELY (MPFR_LIMB_MSB (yp[xn]) == 0))
    {
      count_leading_zeros (cnt, yp[xn]);
      mpn_lshift (yp, yp, xn + 1, cnt);
    }
  else
    {
      cnt = 0;
    }

  /* now yp[xn], ..., yp[0] is msb-normalized too, and has at most
     PREC(x) + (GMP_NUMB_BITS - cnt) non-zero bits */
  MPFR_RNDRAW (inexact, y, yp, (mpfr_prec_t) (xn + 1) * GMP_NUMB_BITS,
               rnd_mode, MPFR_SIGN (x), cnt -- );

  MPFR_TMP_FREE (marker);

  cnt = GMP_NUMB_BITS - cnt;
  if (MPFR_UNLIKELY (__gmpfr_emax < MPFR_EMAX_MIN + cnt
                     || MPFR_GET_EXP (x) > __gmpfr_emax - cnt))
    return mpfr_overflow (y, rnd_mode, MPFR_SIGN(x));

  MPFR_SET_EXP (y, MPFR_GET_EXP (x) + cnt);
  MPFR_SET_SAME_SIGN (y, x);

  return inexact;
}

int
mpfr_fac_ui (mpfr_ptr y, unsigned long int x, mpfr_rnd_t rnd_mode)
{
  mpfr_t t;       /* Variable of Intermediary Calculation*/
  unsigned long i;
  int round, inexact;

  mpfr_prec_t Ny;   /* Precision of output variable */
  mpfr_prec_t Nt;   /* Precision of Intermediary Calculation variable */
  mpfr_prec_t err;  /* Precision of error */

  mpfr_rnd_t rnd;
  MPFR_SAVE_EXPO_DECL (expo);
  MPFR_ZIV_DECL (loop);

  /***** test x = 0  and x == 1******/
  if (MPFR_UNLIKELY (x <= 1))
    return mpfr_set_ui (y, 1, rnd_mode); /* 0! = 1 and 1! = 1 */

  MPFR_SAVE_EXPO_MARK (expo);

  /* Initialisation of the Precision */
  Ny = MPFR_PREC (y);

  /* compute the size of intermediary variable */
  Nt = Ny + 2 * MPFR_INT_CEIL_LOG2 (x) + 7;

  mpfr_init2 (t, Nt); /* initialise of intermediary variable */

  rnd = MPFR_RNDZ;
  MPFR_ZIV_INIT (loop, Nt);
  for (;;)
    {
      /* compute factorial */
      inexact = mpfr_set_ui (t, 1, rnd);
      for (i = 2 ; i <= x ; i++)
        {
          round = mpfr_mul_ui (t, t, i, rnd);
          /* assume the first inexact product gives the sign
             of difference: is that always correct? */
          if (inexact == 0)
            inexact = round;
        }

      err = Nt - 1 - MPFR_INT_CEIL_LOG2 (Nt);

      round = !inexact || mpfr_can_round (t, err, rnd, MPFR_RNDZ,
                                          Ny + (rnd_mode == MPFR_RNDN));

      if (MPFR_LIKELY (round))
        {
          /* If inexact = 0, then t is exactly x!, so round is the
             correct inexact flag.
             Otherwise, t != x! since we rounded to zero or away. */
          round = mpfr_set (y, t, rnd_mode);
          if (inexact == 0)
            {
              inexact = round;
              break;
            }
          else if ((inexact < 0 && round <= 0)
                   || (inexact > 0 && round >= 0))
            break;
          else /* inexact and round have opposite signs: we cannot
                  compute the inexact flag. Restart using the
                  symmetric rounding. */
            rnd = (rnd == MPFR_RNDZ) ? MPFR_RNDU : MPFR_RNDZ;
        }
      MPFR_ZIV_NEXT (loop, Nt);
      mpfr_set_prec (t, Nt);
    }
  MPFR_ZIV_FREE (loop);

  mpfr_clear (t);
  MPFR_SAVE_EXPO_FREE (expo);
  return mpfr_check_range (y, inexact, rnd_mode);
}

/* Implements asymptotic expansion for jn or yn (formulae 9.2.5 and 9.2.6
   from Abramowitz & Stegun).
   Assumes |z| > p log(2)/2, where p is the target precision
   (z can be negative only for jn).
   Return 0 if the expansion does not converge enough (the value 0 as inexact
   flag should not happen for normal input).
*/
static int
FUNCTION (mpfr_ptr res, long n, mpfr_srcptr z, mpfr_rnd_t r)
{
  mpfr_t s, c, P, Q, t, iz, err_t, err_s, err_u;
  mpfr_prec_t w;
  long k;
  int inex, stop, diverge = 0;
  mpfr_exp_t err2, err;
  MPFR_ZIV_DECL (loop);

  mpfr_init (c);

  w = MPFR_PREC(res) + MPFR_INT_CEIL_LOG2(MPFR_PREC(res)) + 4;

  MPFR_ZIV_INIT (loop, w);
  for (;;)
    {
      mpfr_set_prec (c, w);
      mpfr_init2 (s, w);
      mpfr_init2 (P, w);
      mpfr_init2 (Q, w);
      mpfr_init2 (t, w);
      mpfr_init2 (iz, w);
      mpfr_init2 (err_t, 31);
      mpfr_init2 (err_s, 31);
      mpfr_init2 (err_u, 31);

      /* Approximate sin(z) and cos(z). In the following, err <= k means that
         the approximate value y and the true value x are related by
         y = x * (1 + u)^k with |u| <= 2^(-w), following Higham's method. */
      mpfr_sin_cos (s, c, z, MPFR_RNDN);
      if (MPFR_IS_NEG(z))
        mpfr_neg (s, s, MPFR_RNDN); /* compute jn/yn(|z|), fix sign later */
      /* The absolute error on s/c is bounded by 1/2 ulp(1/2) <= 2^(-w-1). */
      mpfr_add (t, s, c, MPFR_RNDN);
      mpfr_sub (c, s, c, MPFR_RNDN);
      mpfr_swap (s, t);
      /* now s approximates sin(z)+cos(z), and c approximates sin(z)-cos(z),
         with total absolute error bounded by 2^(1-w). */

      /* precompute 1/(8|z|) */
      mpfr_si_div (iz, MPFR_IS_POS(z) ? 1 : -1, z, MPFR_RNDN);   /* err <= 1 */
      mpfr_div_2ui (iz, iz, 3, MPFR_RNDN);

      /* compute P and Q */
      mpfr_set_ui (P, 1, MPFR_RNDN);
      mpfr_set_ui (Q, 0, MPFR_RNDN);
      mpfr_set_ui (t, 1, MPFR_RNDN); /* current term */
      mpfr_set_ui (err_t, 0, MPFR_RNDN); /* error on t */
      mpfr_set_ui (err_s, 0, MPFR_RNDN); /* error on P and Q (sum of errors) */
      for (k = 1, stop = 0; stop < 4; k++)
        {
          /* compute next term: t(k)/t(k-1) = (2n+2k-1)(2n-2k+1)/(8kz) */
          mpfr_mul_si (t, t, 2 * (n + k) - 1, MPFR_RNDN); /* err <= err_k + 1 */
          mpfr_mul_si (t, t, 2 * (n - k) + 1, MPFR_RNDN); /* err <= err_k + 2 */
          mpfr_div_ui (t, t, k, MPFR_RNDN);               /* err <= err_k + 3 */
          mpfr_mul (t, t, iz, MPFR_RNDN);                 /* err <= err_k + 5 */
          /* the relative error on t is bounded by (1+u)^(5k)-1, which is
             bounded by 6ku for 6ku <= 0.02: first |5 log(1+u)| <= |5.5u|
             for |u| <= 0.15, then |exp(5.5u)-1| <= 6u for |u| <= 0.02. */
          mpfr_mul_ui (err_t, t, 6 * k, MPFR_IS_POS(t) ? MPFR_RNDU : MPFR_RNDD);
          mpfr_abs (err_t, err_t, MPFR_RNDN); /* exact */
          /* the absolute error on t is bounded by err_t * 2^(-w) */
          mpfr_abs (err_u, t, MPFR_RNDU);
          mpfr_mul_2ui (err_u, err_u, w, MPFR_RNDU); /* t * 2^w */
          mpfr_add (err_u, err_u, err_t, MPFR_RNDU); /* max|t| * 2^w */
          if (stop >= 2)
            {
              /* take into account the neglected terms: t * 2^w */
              mpfr_div_2ui (err_s, err_s, w, MPFR_RNDU);
              if (MPFR_IS_POS(t))
                mpfr_add (err_s, err_s, t, MPFR_RNDU);
              else
                mpfr_sub (err_s, err_s, t, MPFR_RNDU);
              mpfr_mul_2ui (err_s, err_s, w, MPFR_RNDU);
              stop ++;
            }
          /* if k is odd, add to Q, otherwise to P */
          else if (k & 1)
            {
              /* if k = 1 mod 4, add, otherwise subtract */
              if ((k & 2) == 0)
                mpfr_add (Q, Q, t, MPFR_RNDN);
              else
                mpfr_sub (Q, Q, t, MPFR_RNDN);
              /* check if the next term is smaller than ulp(Q): if EXP(err_u)
                 <= EXP(Q), since the current term is bounded by
                 err_u * 2^(-w), it is bounded by ulp(Q) */
              if (MPFR_EXP(err_u) <= MPFR_EXP(Q))
                stop ++;
              else
                stop = 0;
            }
//.........这里部分代码省略.........

int
mpfr_sinh (mpfr_ptr y, mpfr_srcptr xt, mp_rnd_t rnd_mode)
{
  mpfr_t x;
  int inexact;

  MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", xt, xt, rnd_mode),
                 ("y[%#R]=%R inexact=%d", y, y, inexact));

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (xt)))
    {
      if (MPFR_IS_NAN (xt))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else if (MPFR_IS_INF (xt))
        {
          MPFR_SET_INF (y);
          MPFR_SET_SAME_SIGN (y, xt);
          MPFR_RET (0);
        }
      else /* xt is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (xt));
          MPFR_SET_ZERO (y);   /* sinh(0) = 0 */
          MPFR_SET_SAME_SIGN (y, xt);
          MPFR_RET (0);
        }
    }

  /* sinh(x) = x + x^3/6 + ... so the error is < 2^(3*EXP(x)-2) */
  MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, xt, -2 * MPFR_GET_EXP(xt), 2, 1,
                                    rnd_mode, {});

  MPFR_TMP_INIT_ABS (x, xt);

  {
    mpfr_t t, ti;
    mp_exp_t d;
    mp_prec_t Nt;    /* Precision of the intermediary variable */
    long int err;    /* Precision of error */
    MPFR_ZIV_DECL (loop);
    MPFR_SAVE_EXPO_DECL (expo);
    MPFR_GROUP_DECL (group);

    MPFR_SAVE_EXPO_MARK (expo);

    /* compute the precision of intermediary variable */
    Nt = MAX (MPFR_PREC (x), MPFR_PREC (y));
    /* the optimal number of bits : see algorithms.ps */
    Nt = Nt + MPFR_INT_CEIL_LOG2 (Nt) + 4;
    /* If x is near 0, exp(x) - 1/exp(x) = 2*x+x^3/3+O(x^5) */
    if (MPFR_GET_EXP (x) < 0)
      Nt -= 2*MPFR_GET_EXP (x);

    /* initialise of intermediary variables */
    MPFR_GROUP_INIT_2 (group, Nt, t, ti);

    /* First computation of sinh */
    MPFR_ZIV_INIT (loop, Nt);
    for (;;) {
      /* compute sinh */
      mpfr_clear_flags ();
      mpfr_exp (t, x, GMP_RNDD);        /* exp(x) */
      /* exp(x) can overflow! */
      /* BUG/TODO/FIXME: exp can overflow but sinh may be representable! */
      if (MPFR_UNLIKELY (mpfr_overflow_p ())) {
        inexact = mpfr_overflow (y, rnd_mode, MPFR_SIGN (xt));
        MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, MPFR_FLAGS_OVERFLOW);
        break;
      }
      d = MPFR_GET_EXP (t);
      mpfr_ui_div (ti, 1, t, GMP_RNDU); /* 1/exp(x) */
      mpfr_sub (t, t, ti, GMP_RNDN);    /* exp(x) - 1/exp(x) */
      mpfr_div_2ui (t, t, 1, GMP_RNDN);  /* 1/2(exp(x) - 1/exp(x)) */

      /* it may be that t is zero (in fact, it can only occur when te=1,
         and thus ti=1 too) */
      if (MPFR_IS_ZERO (t))
        err = Nt; /* double the precision */
      else
        {
          /* calculation of the error */
          d = d - MPFR_GET_EXP (t) + 2;
          /* error estimate: err = Nt-(__gmpfr_ceil_log2(1+pow(2,d)));*/
          err = Nt - (MAX (d, 0) + 1);
          if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, MPFR_PREC (y), rnd_mode)))
            {
              inexact = mpfr_set4 (y, t, rnd_mode, MPFR_SIGN (xt));
              break;
            }
        }
      /* actualisation of the precision */
      Nt += err;
      MPFR_ZIV_NEXT (loop, Nt);
      MPFR_GROUP_REPREC_2 (group, Nt, t, ti);
    }
    MPFR_ZIV_FREE (loop);
    MPFR_GROUP_CLEAR (group);
//.........这里部分代码省略.........

int
mpfr_cos (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
{
  mpfr_prec_t K0, K, precy, m, k, l;
  int inexact, reduce = 0;
  mpfr_t r, s, xr, c;
  mpfr_exp_t exps, cancel = 0, expx;
  MPFR_ZIV_DECL (loop);
  MPFR_SAVE_EXPO_DECL (expo);
  MPFR_GROUP_DECL (group);

  MPFR_LOG_FUNC (
    ("x[%Pu]=%*.Rg rnd=%d", mpfr_get_prec (x), mpfr_log_prec, x, rnd_mode),
    ("y[%Pu]=%*.Rg inexact=%d", mpfr_get_prec (y), mpfr_log_prec, y,
     inexact));

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    {
      if (MPFR_IS_NAN (x) || MPFR_IS_INF (x))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (x));
          return mpfr_set_ui (y, 1, rnd_mode);
        }
    }

  MPFR_SAVE_EXPO_MARK (expo);

  /* cos(x) = 1-x^2/2 + ..., so error < 2^(2*EXP(x)-1) */
  expx = MPFR_GET_EXP (x);
  MPFR_SMALL_INPUT_AFTER_SAVE_EXPO (y, __gmpfr_one, -2 * expx,
                                    1, 0, rnd_mode, expo, {});

  /* Compute initial precision */
  precy = MPFR_PREC (y);

  if (precy >= MPFR_SINCOS_THRESHOLD)
    {
      MPFR_SAVE_EXPO_FREE (expo);
      return mpfr_cos_fast (y, x, rnd_mode);
    }

  K0 = __gmpfr_isqrt (precy / 3);
  m = precy + 2 * MPFR_INT_CEIL_LOG2 (precy) + 2 * K0;

  if (expx >= 3)
    {
      reduce = 1;
      /* As expx + m - 1 will silently be converted into mpfr_prec_t
         in the mpfr_init2 call, the assert below may be useful to
         avoid undefined behavior. */
      MPFR_ASSERTN (expx + m - 1 <= MPFR_PREC_MAX);
      mpfr_init2 (c, expx + m - 1);
      mpfr_init2 (xr, m);
    }

  MPFR_GROUP_INIT_2 (group, m, r, s);
  MPFR_ZIV_INIT (loop, m);
  for (;;)
    {
      /* If |x| >= 4, first reduce x cmod (2*Pi) into xr, using mpfr_remainder:
         let e = EXP(x) >= 3, and m the target precision:
         (1) c <- 2*Pi              [precision e+m-1, nearest]
         (2) xr <- remainder (x, c) [precision m, nearest]
         We have |c - 2*Pi| <= 1/2ulp(c) = 2^(3-e-m)
                 |xr - x - k c| <= 1/2ulp(xr) <= 2^(1-m)
                 |k| <= |x|/(2*Pi) <= 2^(e-2)
         Thus |xr - x - 2kPi| <= |k| |c - 2Pi| + 2^(1-m) <= 2^(2-m).
         It follows |cos(xr) - cos(x)| <= 2^(2-m). */
      if (reduce)
        {
          mpfr_const_pi (c, MPFR_RNDN);
          mpfr_mul_2ui (c, c, 1, MPFR_RNDN); /* 2Pi */
          mpfr_remainder (xr, x, c, MPFR_RNDN);
          if (MPFR_IS_ZERO(xr))
            goto ziv_next;
          /* now |xr| <= 4, thus r <= 16 below */
          mpfr_mul (r, xr, xr, MPFR_RNDU); /* err <= 1 ulp */
        }
      else
        mpfr_mul (r, x, x, MPFR_RNDU); /* err <= 1 ulp */

      /* now |x| < 4 (or xr if reduce = 1), thus |r| <= 16 */

      /* we need |r| < 1/2 for mpfr_cos2_aux, i.e., EXP(r) - 2K <= -1 */
      K = K0 + 1 + MAX(0, MPFR_GET_EXP(r)) / 2;
      /* since K0 >= 0, if EXP(r) < 0, then K >= 1, thus EXP(r) - 2K <= -3;
         otherwise if EXP(r) >= 0, then K >= 1/2 + EXP(r)/2, thus
         EXP(r) - 2K <= -1 */

      MPFR_SET_EXP (r, MPFR_GET_EXP (r) - 2 * K); /* Can't overflow! */

      /* s <- 1 - r/2! + ... + (-1)^l r^l/(2l)! */
      l = mpfr_cos2_aux (s, r);
      /* l is the error bound in ulps on s */
      MPFR_SET_ONE (r);
//.........这里部分代码省略.........

//.........这里部分代码省略.........
           *   cc: Sun C 5.8 2005/10/13
           *   cc: Sun C 5.8 Patch 121016-02 2006/03/31
           *   cc: Sun C 5.8 Patch 121016-04 2006/10/18
           */
          expy =
            n != -1 && expx > 0 && expx > (__gmpfr_emin - 1) / n ?
            MPFR_EMIN_MIN - 2 /* Underflow */ :
            n != -1 && expx < 0 && expx < (__gmpfr_emax - 1) / n ?
            MPFR_EMAX_MAX /* Overflow */ : n * expx;
          return mpfr_set_si_2exp (y, n % 2 ? MPFR_INT_SIGN (x) : 1,
                                   expy, rnd);
        }

      /* General case */
      {
        /* Declaration of the intermediary variable */
        mpfr_t t;
        /* Declaration of the size variable */
        mpfr_prec_t Ny;                              /* target precision */
        mpfr_prec_t Nt;                              /* working precision */
        mpfr_rnd_t rnd1;
        int size_n;
        int inexact;
        unsigned long abs_n;
        MPFR_SAVE_EXPO_DECL (expo);
        MPFR_ZIV_DECL (loop);

        abs_n = - (unsigned long) n;
        count_leading_zeros (size_n, (mp_limb_t) abs_n);
        size_n = GMP_NUMB_BITS - size_n;

        /* initial working precision */
        Ny = MPFR_PREC (y);
        Nt = Ny + size_n + 3 + MPFR_INT_CEIL_LOG2 (Ny);

        MPFR_SAVE_EXPO_MARK (expo);

        /* initialise of intermediary   variable */
        mpfr_init2 (t, Nt);

        /* We will compute rnd(rnd1(1/x) ^ |n|), where rnd1 is the rounding
           toward sign(x), to avoid spurious overflow or underflow, as in
           mpfr_pow_z. */
        rnd1 = MPFR_EXP (x) < 1 ? MPFR_RNDZ :
          (MPFR_SIGN (x) > 0 ? MPFR_RNDU : MPFR_RNDD);

        MPFR_ZIV_INIT (loop, Nt);
        for (;;)
          {
            MPFR_BLOCK_DECL (flags);

            /* compute (1/x)^|n| */
            MPFR_BLOCK (flags, mpfr_ui_div (t, 1, x, rnd1));
            MPFR_ASSERTD (! MPFR_UNDERFLOW (flags));
            /* t = (1/x)*(1+theta) where |theta| <= 2^(-Nt) */
            if (MPFR_UNLIKELY (MPFR_OVERFLOW (flags)))
              goto overflow;
            MPFR_BLOCK (flags, mpfr_pow_ui (t, t, abs_n, rnd));
            /* t = (1/x)^|n|*(1+theta')^(|n|+1) where |theta'| <= 2^(-Nt).
               If (|n|+1)*2^(-Nt) <= 1/2, which is satisfied as soon as
               Nt >= bits(n)+2, then we can use Lemma \ref{lemma_graillat}
               from algorithms.tex, which yields x^n*(1+theta) with
               |theta| <= 2(|n|+1)*2^(-Nt), thus the error is bounded by
               2(|n|+1) ulps <= 2^(bits(n)+2) ulps. */
            if (MPFR_UNLIKELY (MPFR_OVERFLOW (flags)))
              {

int
mpfr_sin (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
{
  mpfr_t c, xr;
  mpfr_srcptr xx;
  mpfr_exp_t expx, err;
  mpfr_prec_t precy, m;
  int inexact, sign, reduce;
  MPFR_ZIV_DECL (loop);
  MPFR_SAVE_EXPO_DECL (expo);

  MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", x, x, rnd_mode),
                  ("y[%#R]=%R inexact=%d", y, y, inexact));

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    {
      if (MPFR_IS_NAN (x) || MPFR_IS_INF (x))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;

        }
      else /* x is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (x));
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0);
        }
    }

  /* sin(x) = x - x^3/6 + ... so the error is < 2^(3*EXP(x)-2) */
  MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, -2 * MPFR_GET_EXP (x), 2, 0,
                                    rnd_mode, {});

  MPFR_SAVE_EXPO_MARK (expo);

  /* Compute initial precision */
  precy = MPFR_PREC (y);

  if (precy >= MPFR_SINCOS_THRESHOLD)
    return mpfr_sin_fast (y, x, rnd_mode);

  m = precy + MPFR_INT_CEIL_LOG2 (precy) + 13;
  expx = MPFR_GET_EXP (x);

  mpfr_init (c);
  mpfr_init (xr);

  MPFR_ZIV_INIT (loop, m);
  for (;;)
    {
      /* first perform argument reduction modulo 2*Pi (if needed),
         also helps to determine the sign of sin(x) */
      if (expx >= 2) /* If Pi < x < 4, we need to reduce too, to determine
                        the sign of sin(x). For 2 <= |x| < Pi, we could avoid
                        the reduction. */
        {
          reduce = 1;
          /* As expx + m - 1 will silently be converted into mpfr_prec_t
             in the mpfr_set_prec call, the assert below may be useful to
             avoid undefined behavior. */
          MPFR_ASSERTN (expx + m - 1 <= MPFR_PREC_MAX);
          mpfr_set_prec (c, expx + m - 1);
          mpfr_set_prec (xr, m);
          mpfr_const_pi (c, MPFR_RNDN);
          mpfr_mul_2ui (c, c, 1, MPFR_RNDN);
          mpfr_remainder (xr, x, c, MPFR_RNDN);
          /* The analysis is similar to that of cos.c:
             |xr - x - 2kPi| <= 2^(2-m). Thus we can decide the sign
             of sin(x) if xr is at distance at least 2^(2-m) of both
             0 and +/-Pi. */
          mpfr_div_2ui (c, c, 1, MPFR_RNDN);
          /* Since c approximates Pi with an error <= 2^(2-expx-m) <= 2^(-m),
             it suffices to check that c - |xr| >= 2^(2-m). */
          if (MPFR_SIGN (xr) > 0)
            mpfr_sub (c, c, xr, MPFR_RNDZ);
          else
            mpfr_add (c, c, xr, MPFR_RNDZ);
          if (MPFR_IS_ZERO(xr)
              || MPFR_EXP(xr) < (mpfr_exp_t) 3 - (mpfr_exp_t) m
              || MPFR_EXP(c) < (mpfr_exp_t) 3 - (mpfr_exp_t) m)
            goto ziv_next;

          /* |xr - x - 2kPi| <= 2^(2-m), thus |sin(xr) - sin(x)| <= 2^(2-m) */
          xx = xr;
        }
      else /* the input argument is already reduced */
        {
          reduce = 0;
          xx = x;
        }

      sign = MPFR_SIGN(xx);
      /* now that the argument is reduced, precision m is enough */
      mpfr_set_prec (c, m);
      mpfr_cos (c, xx, MPFR_RNDZ);    /* can't be exact */
      mpfr_nexttoinf (c);           /* now c = cos(x) rounded away */
      mpfr_mul (c, c, c, MPFR_RNDU); /* away */
      mpfr_ui_sub (c, 1, c, MPFR_RNDZ);
//.........这里部分代码省略.........

int
mpfr_log (mpfr_ptr r, mpfr_srcptr a, mpfr_rnd_t rnd_mode)
{
  int inexact;
  mpfr_prec_t p, q;
  mpfr_t tmp1, tmp2;
  MPFR_SAVE_EXPO_DECL (expo);
  MPFR_ZIV_DECL (loop);
  MPFR_GROUP_DECL(group);

  MPFR_LOG_FUNC
    (("a[%Pu]=%.*Rg rnd=%d", mpfr_get_prec (a), mpfr_log_prec, a, rnd_mode),
     ("r[%Pu]=%.*Rg inexact=%d", mpfr_get_prec (r), mpfr_log_prec, r,
      inexact));

  /* Special cases */
  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (a)))
    {
      /* If a is NaN, the result is NaN */
      if (MPFR_IS_NAN (a))
        {
          MPFR_SET_NAN (r);
          MPFR_RET_NAN;
        }
      /* check for infinity before zero */
      else if (MPFR_IS_INF (a))
        {
          if (MPFR_IS_NEG (a))
            /* log(-Inf) = NaN */
            {
              MPFR_SET_NAN (r);
              MPFR_RET_NAN;
            }
          else /* log(+Inf) = +Inf */
            {
              MPFR_SET_INF (r);
              MPFR_SET_POS (r);
              MPFR_RET (0);
            }
        }
      else /* a is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (a));
          MPFR_SET_INF (r);
          MPFR_SET_NEG (r);
          mpfr_set_divby0 ();
          MPFR_RET (0); /* log(0) is an exact -infinity */
        }
    }
  /* If a is negative, the result is NaN */
  else if (MPFR_UNLIKELY (MPFR_IS_NEG (a)))
    {
      MPFR_SET_NAN (r);
      MPFR_RET_NAN;
    }
  /* If a is 1, the result is 0 */
  else if (MPFR_UNLIKELY (MPFR_GET_EXP (a) == 1 && mpfr_cmp_ui (a, 1) == 0))
    {
      MPFR_SET_ZERO (r);
      MPFR_SET_POS (r);
      MPFR_RET (0); /* only "normal" case where the result is exact */
    }

  q = MPFR_PREC (r);

  /* use initial precision about q+lg(q)+5 */
  p = q + 5 + 2 * MPFR_INT_CEIL_LOG2 (q);
  /* % ~(mpfr_prec_t)GMP_NUMB_BITS  ;
     m=q; while (m) { p++; m >>= 1; }  */
  /* if (MPFR_LIKELY(p % GMP_NUMB_BITS != 0))
      p += GMP_NUMB_BITS - (p%GMP_NUMB_BITS); */

  MPFR_SAVE_EXPO_MARK (expo);
  MPFR_GROUP_INIT_2 (group, p, tmp1, tmp2);

  MPFR_ZIV_INIT (loop, p);
  for (;;)
    {
      long m;
      mpfr_exp_t cancel;

      /* Calculus of m (depends on p) */
      m = (p + 1) / 2 - MPFR_GET_EXP (a) + 1;

      mpfr_mul_2si (tmp2, a, m, MPFR_RNDN);    /* s=a*2^m,        err<=1 ulp  */
      mpfr_div (tmp1, __gmpfr_four, tmp2, MPFR_RNDN);/* 4/s,      err<=2 ulps */
      mpfr_agm (tmp2, __gmpfr_one, tmp1, MPFR_RNDN); /* AG(1,4/s),err<=3 ulps */
      mpfr_mul_2ui (tmp2, tmp2, 1, MPFR_RNDN); /* 2*AG(1,4/s),    err<=3 ulps */
      mpfr_const_pi (tmp1, MPFR_RNDN);         /* compute pi,     err<=1ulp   */
      mpfr_div (tmp2, tmp1, tmp2, MPFR_RNDN);  /* pi/2*AG(1,4/s), err<=5ulps  */
      mpfr_const_log2 (tmp1, MPFR_RNDN);      /* compute log(2),  err<=1ulp   */
      mpfr_mul_si (tmp1, tmp1, m, MPFR_RNDN); /* compute m*log(2),err<=2ulps  */
      mpfr_sub (tmp1, tmp2, tmp1, MPFR_RNDN); /* log(a),    err<=7ulps+cancel */

      if (MPFR_LIKELY (MPFR_IS_PURE_FP (tmp1) && MPFR_IS_PURE_FP (tmp2)))
        {
          cancel = MPFR_GET_EXP (tmp2) - MPFR_GET_EXP (tmp1);
          MPFR_LOG_MSG (("canceled bits=%ld\n", (long) cancel));
          MPFR_LOG_VAR (tmp1);
          if (MPFR_UNLIKELY (cancel < 0))
//.........这里部分代码省略.........

int
mpfr_log10 (mpfr_ptr r, mpfr_srcptr a, mpfr_rnd_t rnd_mode)
{
  int inexact;
  MPFR_SAVE_EXPO_DECL (expo);

  /* If a is NaN, the result is NaN */
  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (a)))
    {
      if (MPFR_IS_NAN (a))
        {
          MPFR_SET_NAN (r);
          MPFR_RET_NAN;
        }
      /* check for infinity before zero */
      else if (MPFR_IS_INF (a))
        {
          if (MPFR_IS_NEG (a))
            /* log10(-Inf) = NaN */
            {
              MPFR_SET_NAN (r);
              MPFR_RET_NAN;
            }
          else /* log10(+Inf) = +Inf */
            {
              MPFR_SET_INF (r);
              MPFR_SET_POS (r);
              MPFR_RET (0); /* exact */
            }
        }
      else /* a = 0 */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO (a));
          MPFR_SET_INF (r);
          MPFR_SET_NEG (r);
          MPFR_RET (0); /* log10(0) is an exact -infinity */
        }
    }

  /* If a is negative, the result is NaN */
  if (MPFR_UNLIKELY (MPFR_IS_NEG (a)))
    {
      MPFR_SET_NAN (r);
      MPFR_RET_NAN;
    }

  /* If a is 1, the result is 0 */
  if (mpfr_cmp_ui (a, 1) == 0)
    {
      MPFR_SET_ZERO (r);
      MPFR_SET_POS (r);
      MPFR_RET (0); /* result is exact */
    }

  MPFR_SAVE_EXPO_MARK (expo);

  /* General case */
  {
    /* Declaration of the intermediary variable */
    mpfr_t t, tt;
    MPFR_ZIV_DECL (loop);
    /* Declaration of the size variable */
    mpfr_prec_t Ny = MPFR_PREC(r);   /* Precision of output variable */
    mpfr_prec_t Nt;        /* Precision of the intermediary variable */
    mpfr_exp_t  err;                           /* Precision of error */

    /* compute the precision of intermediary variable */
    /* the optimal number of bits : see algorithms.tex */
    Nt = Ny + 4 + MPFR_INT_CEIL_LOG2 (Ny);

    /* initialise of intermediary variables */
    mpfr_init2 (t, Nt);
    mpfr_init2 (tt, Nt);

    /* First computation of log10 */
    MPFR_ZIV_INIT (loop, Nt);
    for (;;)
      {
        /* compute log10 */
        mpfr_set_ui (t, 10, MPFR_RNDN);   /* 10 */
        mpfr_log (t, t, MPFR_RNDD);       /* log(10) */
        mpfr_log (tt, a, MPFR_RNDN);      /* log(a) */
        mpfr_div (t, tt, t, MPFR_RNDN);   /* log(a)/log(10) */

        /* estimation of the error */
        err = Nt - 4;
        if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
          break;

        /* log10(10^n) is exact:
           FIXME: Can we have 10^n exactly representable as a mpfr_t
           but n can't fit an unsigned long? */
        if (MPFR_IS_POS (t)
            && mpfr_integer_p (t) && mpfr_fits_ulong_p (t, MPFR_RNDN)
            && !mpfr_ui_pow_ui (tt, 10, mpfr_get_ui (t, MPFR_RNDN), MPFR_RNDN)
            && mpfr_cmp (a, tt) == 0)
          break;

        /* actualisation of the precision */
        MPFR_ZIV_NEXT (loop, Nt);
//.........这里部分代码省略.........

/* returns 0 if result exact, non-zero otherwise */
int
mpfr_div_ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int u, mpfr_rnd_t rnd_mode)
{
  long i;
  int sh;
  mp_size_t xn, yn, dif;
  mp_limb_t *xp, *yp, *tmp, c, d;
  mpfr_exp_t exp;
  int inexact, middle = 1, nexttoinf;
  MPFR_TMP_DECL(marker);

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    {
      if (MPFR_IS_NAN (x))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else if (MPFR_IS_INF (x))
        {
          MPFR_SET_INF (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0);
        }
      else
        {
          MPFR_ASSERTD (MPFR_IS_ZERO(x));
          if (u == 0) /* 0/0 is NaN */
            {
              MPFR_SET_NAN(y);
              MPFR_RET_NAN;
            }
          else
            {
              MPFR_SET_ZERO(y);
              MPFR_SET_SAME_SIGN (y, x);
              MPFR_RET(0);
            }
        }
    }
  else if (MPFR_UNLIKELY (u <= 1))
    {
      if (u < 1)
        {
          /* x/0 is Inf since x != 0*/
          MPFR_SET_INF (y);
          MPFR_SET_SAME_SIGN (y, x);
          MPFR_RET (0);
        }
      else /* y = x/1 = x */
        return mpfr_set (y, x, rnd_mode);
    }
  else if (MPFR_UNLIKELY (IS_POW2 (u)))
    return mpfr_div_2si (y, x, MPFR_INT_CEIL_LOG2 (u), rnd_mode);

  MPFR_SET_SAME_SIGN (y, x);

  MPFR_TMP_MARK (marker);
  xn = MPFR_LIMB_SIZE (x);
  yn = MPFR_LIMB_SIZE (y);

  xp = MPFR_MANT (x);
  yp = MPFR_MANT (y);
  exp = MPFR_GET_EXP (x);

  dif = yn + 1 - xn;

  /* we need to store yn+1 = xn + dif limbs of the quotient */
  /* don't use tmp=yp since the mpn_lshift call below requires yp >= tmp+1 */
  tmp = (mp_limb_t*) MPFR_TMP_ALLOC ((yn + 1) * BYTES_PER_MP_LIMB);

  c = (mp_limb_t) u;
  MPFR_ASSERTN (u == c);
  if (dif >= 0)
    c = mpn_divrem_1 (tmp, dif, xp, xn, c); /* used all the dividend */
  else /* dif < 0 i.e. xn > yn, don't use the (-dif) low limbs from x */
    c = mpn_divrem_1 (tmp, 0, xp - dif, yn + 1, c);

  inexact = (c != 0);

  /* First pass in estimating next bit of the quotient, in case of RNDN    *
   * In case we just have the right number of bits (postpone this ?),      *
   * we need to check whether the remainder is more or less than half      *
   * the divisor. The test must be performed with a subtraction, so as     *
   * to prevent carries.                                                   */

  if (MPFR_LIKELY (rnd_mode == MPFR_RNDN))
    {
      if (c < (mp_limb_t) u - c) /* We have u > c */
        middle = -1;
      else if (c > (mp_limb_t) u - c)
        middle = 1;
      else
        middle = 0; /* exactly in the middle */
    }

  /* If we believe that we are right in the middle or exact, we should check
     that we did not neglect any word of x (division large / 1 -> small). */

//.........这里部分代码省略.........

int
mpfr_tanh (mpfr_ptr y, mpfr_srcptr xt , mpfr_rnd_t rnd_mode)
{
  /****** Declaration ******/
  mpfr_t x;
  int inexact;
  MPFR_SAVE_EXPO_DECL (expo);

  MPFR_LOG_FUNC
    (("x[%Pu]=%.*Rg rnd=%d", mpfr_get_prec (xt), mpfr_log_prec, xt, rnd_mode),
     ("y[%Pu]=%.*Rg inexact=%d",
      mpfr_get_prec (y), mpfr_log_prec, y, inexact));

  /* Special value checking */
  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (xt)))
    {
      if (MPFR_IS_NAN (xt))
        {
          MPFR_SET_NAN (y);
          MPFR_RET_NAN;
        }
      else if (MPFR_IS_INF (xt))
        {
          /* tanh(inf) = 1 && tanh(-inf) = -1 */
          return mpfr_set_si (y, MPFR_INT_SIGN (xt), rnd_mode);
        }
      else /* tanh (0) = 0 and xt is zero */
        {
          MPFR_ASSERTD (MPFR_IS_ZERO(xt));
          MPFR_SET_ZERO (y);
          MPFR_SET_SAME_SIGN (y, xt);
          MPFR_RET (0);
        }
    }

  /* tanh(x) = x - x^3/3 + ... so the error is < 2^(3*EXP(x)-1) */
  MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, xt, -2 * MPFR_GET_EXP (xt), 1, 0,
                                    rnd_mode, {});

  MPFR_TMP_INIT_ABS (x, xt);

  MPFR_SAVE_EXPO_MARK (expo);

  /* General case */
  {
    /* Declaration of the intermediary variable */
    mpfr_t t, te;
    mpfr_exp_t d;

    /* Declaration of the size variable */
    mpfr_prec_t Ny = MPFR_PREC(y);   /* target precision */
    mpfr_prec_t Nt;                  /* working precision */
    long int err;                  /* error */
    int sign = MPFR_SIGN (xt);
    MPFR_ZIV_DECL (loop);
    MPFR_GROUP_DECL (group);

    /* First check for BIG overflow of exp(2*x):
       For x > 0, exp(2*x) > 2^(2*x)
       If 2 ^(2*x) > 2^emax or x>emax/2, there is an overflow */
    if (MPFR_UNLIKELY (mpfr_cmp_si (x, __gmpfr_emax/2) >= 0)) {
      /* initialise of intermediary variables
         since 'set_one' label assumes the variables have been
         initialize */
      MPFR_GROUP_INIT_2 (group, MPFR_PREC_MIN, t, te);
      goto set_one;
    }

    /* Compute the precision of intermediary variable */
    /* The optimal number of bits: see algorithms.tex */
    Nt = Ny + MPFR_INT_CEIL_LOG2 (Ny) + 4;
    /* if x is small, there will be a cancellation in exp(2x)-1 */
    if (MPFR_GET_EXP (x) < 0)
      Nt += -MPFR_GET_EXP (x);

    /* initialise of intermediary variable */
    MPFR_GROUP_INIT_2 (group, Nt, t, te);

    MPFR_ZIV_INIT (loop, Nt);
    for (;;) {
      /* tanh = (exp(2x)-1)/(exp(2x)+1) */
      mpfr_mul_2ui (te, x, 1, MPFR_RNDN);  /* 2x */
      /* since x > 0, we can only have an overflow */
      mpfr_exp (te, te, MPFR_RNDN);        /* exp(2x) */
      if (MPFR_UNLIKELY (MPFR_IS_INF (te))) {
      set_one:
        inexact = MPFR_FROM_SIGN_TO_INT (sign);
        mpfr_set4 (y, __gmpfr_one, MPFR_RNDN, sign);
        if (MPFR_IS_LIKE_RNDZ (rnd_mode, MPFR_IS_NEG_SIGN (sign)))
          {
            inexact = -inexact;
            mpfr_nexttozero (y);
          }
        break;
      }
      d = MPFR_GET_EXP (te);              /* For Error calculation */
      mpfr_add_ui (t, te, 1, MPFR_RNDD);   /* exp(2x) + 1*/
      mpfr_sub_ui (te, te, 1, MPFR_RNDU);  /* exp(2x) - 1*/
      d = d - MPFR_GET_EXP (te);
      mpfr_div (t, te, t, MPFR_RNDN);      /* (exp(2x)-1)/(exp(2x)+1)*/
//.........这里部分代码省略.........