int
mpfr_atanh (mpfr_ptr y, mpfr_srcptr xt , mpfr_rnd_t rnd_mode)
{
int inexact;
mpfr_t x, t, te;
mpfr_prec_t Nx, Ny, Nt;
mpfr_exp_t err;
MPFR_ZIV_DECL (loop);
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 cases */
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (xt)))
{
/* atanh(NaN) = NaN, and atanh(+/-Inf) = NaN since tanh gives a result
between -1 and 1 */
if (MPFR_IS_NAN (xt) || MPFR_IS_INF (xt))
{
MPFR_SET_NAN (y);
MPFR_RET_NAN;
}
else /* necessarily xt is 0 */
{
MPFR_ASSERTD (MPFR_IS_ZERO (xt));
MPFR_SET_ZERO (y); /* atanh(0) = 0 */
MPFR_SET_SAME_SIGN (y,xt);
MPFR_RET (0);
}
}
/* atanh (x) = NaN as soon as |x| > 1, and arctanh(+/-1) = +/-Inf */
if (MPFR_UNLIKELY (MPFR_GET_EXP (xt) > 0))
{
if (MPFR_GET_EXP (xt) == 1 && mpfr_powerof2_raw (xt))
{
MPFR_SET_INF (y);
MPFR_SET_SAME_SIGN (y, xt);
mpfr_set_divby0 ();
MPFR_RET (0);
}
MPFR_SET_NAN (y);
MPFR_RET_NAN;
}
/* atanh(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, 1,
rnd_mode, {});
MPFR_SAVE_EXPO_MARK (expo);
/* Compute initial precision */
Nx = MPFR_PREC (xt);
MPFR_TMP_INIT_ABS (x, xt);
Ny = MPFR_PREC (y);
Nt = MAX (Nx, Ny);
/* the optimal number of bits : see algorithms.ps */
Nt = Nt + MPFR_INT_CEIL_LOG2 (Nt) + 4;
/* initialise of intermediary variable */
mpfr_init2 (t, Nt);
mpfr_init2 (te, Nt);
/* First computation of cosh */
MPFR_ZIV_INIT (loop, Nt);
for (;;)
{
/* compute atanh */
mpfr_ui_sub (te, 1, x, MPFR_RNDU); /* (1-xt)*/
mpfr_add_ui (t, x, 1, MPFR_RNDD); /* (xt+1)*/
mpfr_div (t, t, te, MPFR_RNDN); /* (1+xt)/(1-xt)*/
mpfr_log (t, t, MPFR_RNDN); /* ln((1+xt)/(1-xt))*/
mpfr_div_2ui (t, t, 1, MPFR_RNDN); /* (1/2)*ln((1+xt)/(1-xt))*/
/* error estimate: see algorithms.tex */
/* FIXME: this does not correspond to the value in algorithms.tex!!! */
/* err=Nt-__gmpfr_ceil_log2(1+5*pow(2,1-MPFR_EXP(t)));*/
err = Nt - (MAX (4 - MPFR_GET_EXP (t), 0) + 1);
if (MPFR_LIKELY (MPFR_IS_ZERO (t)
|| MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
break;
/* reactualisation of the precision */
MPFR_ZIV_NEXT (loop, Nt);
mpfr_set_prec (t, Nt);
mpfr_set_prec (te, Nt);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set4 (y, t, rnd_mode, MPFR_SIGN (xt));
mpfr_clear(t);
mpfr_clear(te);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
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);
MPFR_SAVE_EXPO_FREE (expo);
}
return mpfr_check_range (y, inexact, rnd_mode);
}
int
mpfr_log1p (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode)
{
int comp, inexact;
mp_exp_t ex;
MPFR_SAVE_EXPO_DECL (expo);
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
{
if (MPFR_IS_NAN (x))
{
MPFR_SET_NAN (y);
MPFR_RET_NAN;
}
/* check for inf or -inf (result is not defined) */
else if (MPFR_IS_INF (x))
{
if (MPFR_IS_POS (x))
{
MPFR_SET_INF (y);
MPFR_SET_POS (y);
MPFR_RET (0);
}
else
{
MPFR_SET_NAN (y);
MPFR_RET_NAN;
}
}
else /* x is zero */
{
MPFR_ASSERTD (MPFR_IS_ZERO (x));
MPFR_SET_ZERO (y); /* log1p(+/- 0) = +/- 0 */
MPFR_SET_SAME_SIGN (y, x);
MPFR_RET (0);
}
}
ex = MPFR_GET_EXP (x);
if (ex < 0) /* -0.5 < x < 0.5 */
{
/* For x > 0, abs(log(1+x)-x) < x^2/2.
For x > -0.5, abs(log(1+x)-x) < x^2. */
if (MPFR_IS_POS (x))
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, - ex - 1, 0, 0, rnd_mode, {});
else
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, - ex, 0, 1, rnd_mode, {});
}
comp = mpfr_cmp_si (x, -1);
/* log1p(x) is undefined for x < -1 */
if (MPFR_UNLIKELY(comp <= 0))
{
if (comp == 0)
/* x=0: log1p(-1)=-inf (division by zero) */
{
MPFR_SET_INF (y);
MPFR_SET_NEG (y);
MPFR_RET (0);
}
MPFR_SET_NAN (y);
MPFR_RET_NAN;
}
MPFR_SAVE_EXPO_MARK (expo);
/* General case */
{
/* Declaration of the intermediary variable */
mpfr_t t;
/* Declaration of the size variable */
mp_prec_t Ny = MPFR_PREC(y); /* target precision */
mp_prec_t Nt; /* working precision */
mp_exp_t err; /* error */
MPFR_ZIV_DECL (loop);
/* compute the precision of intermediary variable */
/* the optimal number of bits : see algorithms.tex */
Nt = Ny + MPFR_INT_CEIL_LOG2 (Ny) + 6;
/* if |x| is smaller than 2^(-e), we will loose about e bits
in log(1+x) */
if (MPFR_EXP(x) < 0)
Nt += -MPFR_EXP(x);
/* initialise of intermediary variable */
mpfr_init2 (t, Nt);
/* First computation of log1p */
MPFR_ZIV_INIT (loop, Nt);
for (;;)
{
/* compute log1p */
inexact = mpfr_add_ui (t, x, 1, GMP_RNDN); /* 1+x */
/* if inexact = 0, then t = x+1, and the result is simply log(t) */
if (inexact == 0)
{
inexact = mpfr_log (y, t, rnd_mode);
goto end;
}
mpfr_log (t, t, GMP_RNDN); /* log(1+x) */
/* the error is bounded by (1/2+2^(1-EXP(t))*ulp(t) (cf algorithms.tex)
if EXP(t)>=2, then error <= ulp(t)
if EXP(t)<=1, then error <= 2^(2-EXP(t))*ulp(t) */
err = Nt - MAX (0, 2 - MPFR_GET_EXP (t));
if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
break;
/* increase the precision */
MPFR_ZIV_NEXT (loop, Nt);
mpfr_set_prec (t, Nt);
}
inexact = mpfr_set (y, t, rnd_mode);
end:
MPFR_ZIV_FREE (loop);
mpfr_clear (t);
}
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
int
mpfr_asin (mpfr_ptr asin, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
{
mpfr_t xp;
int compared, inexact;
mpfr_prec_t prec;
mpfr_exp_t xp_exp;
MPFR_SAVE_EXPO_DECL (expo);
MPFR_ZIV_DECL (loop);
MPFR_LOG_FUNC (
("x[%Pu]=%.*Rg rnd=%d", mpfr_get_prec (x), mpfr_log_prec, x, rnd_mode),
("asin[%Pu]=%.*Rg inexact=%d", mpfr_get_prec (asin), mpfr_log_prec, asin,
inexact));
/* Special cases */
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
{
if (MPFR_IS_NAN (x) || MPFR_IS_INF (x))
{
MPFR_SET_NAN (asin);
MPFR_RET_NAN;
}
else /* x = 0 */
{
MPFR_ASSERTD (MPFR_IS_ZERO (x));
MPFR_SET_ZERO (asin);
MPFR_SET_SAME_SIGN (asin, x);
MPFR_RET (0); /* exact result */
}
}
/* asin(x) = x + x^3/6 + ... so the error is < 2^(3*EXP(x)-2) */
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (asin, x, -2 * MPFR_GET_EXP (x), 2, 1,
rnd_mode, {});
/* Set x_p=|x| (x is a normal number) */
mpfr_init2 (xp, MPFR_PREC (x));
inexact = mpfr_abs (xp, x, MPFR_RNDN);
MPFR_ASSERTD (inexact == 0);
compared = mpfr_cmp_ui (xp, 1);
MPFR_SAVE_EXPO_MARK (expo);
if (MPFR_UNLIKELY (compared >= 0))
{
mpfr_clear (xp);
if (compared > 0) /* asin(x) = NaN for |x| > 1 */
{
MPFR_SAVE_EXPO_FREE (expo);
MPFR_SET_NAN (asin);
MPFR_RET_NAN;
}
else /* x = 1 or x = -1 */
{
if (MPFR_IS_POS (x)) /* asin(+1) = Pi/2 */
inexact = mpfr_const_pi (asin, rnd_mode);
else /* asin(-1) = -Pi/2 */
{
inexact = -mpfr_const_pi (asin, MPFR_INVERT_RND(rnd_mode));
MPFR_CHANGE_SIGN (asin);
}
mpfr_div_2ui (asin, asin, 1, rnd_mode);
}
}
else
{
/* Compute exponent of 1 - ABS(x) */
mpfr_ui_sub (xp, 1, xp, MPFR_RNDD);
MPFR_ASSERTD (MPFR_GET_EXP (xp) <= 0);
MPFR_ASSERTD (MPFR_GET_EXP (x) <= 0);
xp_exp = 2 - MPFR_GET_EXP (xp);
/* Set up initial prec */
prec = MPFR_PREC (asin) + 10 + xp_exp;
/* use asin(x) = atan(x/sqrt(1-x^2)) */
MPFR_ZIV_INIT (loop, prec);
for (;;)
{
mpfr_set_prec (xp, prec);
mpfr_sqr (xp, x, MPFR_RNDN);
mpfr_ui_sub (xp, 1, xp, MPFR_RNDN);
mpfr_sqrt (xp, xp, MPFR_RNDN);
mpfr_div (xp, x, xp, MPFR_RNDN);
mpfr_atan (xp, xp, MPFR_RNDN);
if (MPFR_LIKELY (MPFR_CAN_ROUND (xp, prec - xp_exp,
MPFR_PREC (asin), rnd_mode)))
break;
MPFR_ZIV_NEXT (loop, prec);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (asin, xp, rnd_mode);
mpfr_clear (xp);
}
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (asin, inexact, rnd_mode);
}
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)*/
/* Calculation of the error */
d = MAX(3, d + 1);
err = Nt - (d + 1);
if (MPFR_LIKELY ((d <= Nt / 2) && MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
{
inexact = mpfr_set4 (y, t, rnd_mode, sign);
break;
}
/* if t=1, we still can round since |sinh(x)| < 1 */
if (MPFR_GET_EXP (t) == 1)
goto set_one;
/* Actualisation of the precision */
MPFR_ZIV_NEXT (loop, Nt);
MPFR_GROUP_REPREC_2 (group, Nt, t, te);
}
MPFR_ZIV_FREE (loop);
MPFR_GROUP_CLEAR (group);
}
MPFR_SAVE_EXPO_FREE (expo);
inexact = mpfr_check_range (y, inexact, rnd_mode);
return inexact;
}
int
mpfr_sinh (mpfr_ptr y, mpfr_srcptr xt, mpfr_rnd_t rnd_mode)
{
mpfr_t x;
int inexact;
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));
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;
mpfr_exp_t d;
mpfr_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 (;;)
{
MPFR_BLOCK_DECL (flags);
/* compute sinh */
MPFR_BLOCK (flags, mpfr_exp (t, x, MPFR_RNDD));
if (MPFR_OVERFLOW (flags))
/* exp(x) does overflow */
{
/* sinh(x) = 2 * sinh(x/2) * cosh(x/2) */
mpfr_div_2ui (ti, x, 1, MPFR_RNDD); /* exact */
/* t <- cosh(x/2): error(t) <= 1 ulp(t) */
MPFR_BLOCK (flags, mpfr_cosh (t, ti, MPFR_RNDD));
if (MPFR_OVERFLOW (flags))
/* when x>1 we have |sinh(x)| >= cosh(x/2), so sinh(x)
overflows too */
{
inexact = mpfr_overflow (y, rnd_mode, MPFR_SIGN (xt));
MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, MPFR_FLAGS_OVERFLOW);
break;
}
/* ti <- sinh(x/2): , error(ti) <= 1 ulp(ti)
cannot overflow because 0 < sinh(x) < cosh(x) when x > 0 */
mpfr_sinh (ti, ti, MPFR_RNDD);
/* multiplication below, error(t) <= 5 ulp(t) */
MPFR_BLOCK (flags, mpfr_mul (t, t, ti, MPFR_RNDD));
if (MPFR_OVERFLOW (flags))
{
inexact = mpfr_overflow (y, rnd_mode, MPFR_SIGN (xt));
MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, MPFR_FLAGS_OVERFLOW);
break;
}
/* doubling below, exact */
MPFR_BLOCK (flags, mpfr_mul_2ui (t, t, 1, MPFR_RNDN));
if (MPFR_OVERFLOW (flags))
{
inexact = mpfr_overflow (y, rnd_mode, MPFR_SIGN (xt));
MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, MPFR_FLAGS_OVERFLOW);
break;
}
/* we have lost at most 3 bits of precision */
err = Nt - 3;
if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, MPFR_PREC (y),
rnd_mode)))
{
inexact = mpfr_set4 (y, t, rnd_mode, MPFR_SIGN (xt));
break;
}
err = Nt; /* double the precision */
}
else
{
d = MPFR_GET_EXP (t);
mpfr_ui_div (ti, 1, t, MPFR_RNDU); /* 1/exp(x) */
mpfr_sub (t, t, ti, MPFR_RNDN); /* exp(x) - 1/exp(x) */
mpfr_div_2ui (t, t, 1, MPFR_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);
MPFR_SAVE_EXPO_FREE (expo);
}
return mpfr_check_range (y, inexact, rnd_mode);
}
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);
mpfr_sqrt (c, c, MPFR_RNDZ);
if (MPFR_IS_NEG_SIGN(sign))
MPFR_CHANGE_SIGN(c);
/* Warning: c may be 0! */
if (MPFR_UNLIKELY (MPFR_IS_ZERO (c)))
{
/* Huge cancellation: increase prec a lot! */
m = MAX (m, MPFR_PREC (x));
m = 2 * m;
}
else
{
/* the absolute error on c is at most 2^(3-m-EXP(c)),
plus 2^(2-m) if there was an argument reduction.
Since EXP(c) <= 1, 3-m-EXP(c) >= 2-m, thus the error
is at most 2^(3-m-EXP(c)) in case of argument reduction. */
err = 2 * MPFR_GET_EXP (c) + (mpfr_exp_t) m - 3 - (reduce != 0);
if (MPFR_CAN_ROUND (c, err, precy, rnd_mode))
break;
/* check for huge cancellation (Near 0) */
if (err < (mpfr_exp_t) MPFR_PREC (y))
m += MPFR_PREC (y) - err;
/* Check if near 1 */
if (MPFR_GET_EXP (c) == 1)
m += m;
}
ziv_next:
/* Else generic increase */
MPFR_ZIV_NEXT (loop, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, c, rnd_mode);
/* inexact cannot be 0, since this would mean that c was representable
within the target precision, but in that case mpfr_can_round will fail */
mpfr_clear (c);
mpfr_clear (xr);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
/* computes tan(x) = sign(x)*sqrt(1/cos(x)^2-1) */
int
mpfr_tan (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode)
{
mp_prec_t precy, m;
int inexact;
mpfr_t s, c;
MPFR_ZIV_DECL (loop);
MPFR_SAVE_EXPO_DECL (expo);
MPFR_GROUP_DECL (group);
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);
}
}
/* tan(x) = x + x^3/3 + ... so the error is < 2^(3*EXP(x)-1) */
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, -2 * MPFR_GET_EXP (x), 1, 1,
rnd_mode, {});
MPFR_SAVE_EXPO_MARK (expo);
/* Compute initial precision */
precy = MPFR_PREC (y);
m = precy + MPFR_INT_CEIL_LOG2 (precy) + 13;
MPFR_ASSERTD (m >= 2); /* needed for the error analysis in algorithms.tex */
MPFR_GROUP_INIT_2 (group, m, s, c);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
/* The only way to get an overflow is to get ~ Pi/2
But the result will be ~ 2^Prec(y). */
mpfr_sin_cos (s, c, x, GMP_RNDN); /* err <= 1/2 ulp on s and c */
mpfr_div (c, s, c, GMP_RNDN); /* err <= 4 ulps */
MPFR_ASSERTD (!MPFR_IS_SINGULAR (c));
if (MPFR_LIKELY (MPFR_CAN_ROUND (c, m - 2, precy, rnd_mode)))
break;
MPFR_ZIV_NEXT (loop, m);
MPFR_GROUP_REPREC_2 (group, m, s, c);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, c, rnd_mode);
MPFR_GROUP_CLEAR (group);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
/* Input: s - a floating-point number >= 1/2.
rnd_mode - a rounding mode.
Assumes s is neither NaN nor Infinite.
Output: z - Zeta(s) rounded to the precision of z with direction rnd_mode
*/
static int
mpfr_zeta_pos (mpfr_t z, mpfr_srcptr s, mp_rnd_t rnd_mode)
{
mpfr_t b, c, z_pre, f, s1;
double beta, sd, dnep;
mpfr_t *tc1;
mp_prec_t precz, precs, d, dint;
int p, n, l, add;
int inex;
MPFR_GROUP_DECL (group);
MPFR_ZIV_DECL (loop);
MPFR_ASSERTD (MPFR_IS_POS (s) && MPFR_GET_EXP (s) >= 0);
precz = MPFR_PREC (z);
precs = MPFR_PREC (s);
/* Zeta(x) = 1+1/2^x+1/3^x+1/4^x+1/5^x+O(1/6^x)
so with 2^(EXP(x)-1) <= x < 2^EXP(x)
So for x > 2^3, k^x > k^8, so 2/k^x < 2/k^8
Zeta(x) = 1 + 1/2^x*(1+(2/3)^x+(2/4)^x+...)
= 1 + 1/2^x*(1+sum((2/k)^x,k=3..infinity))
<= 1 + 1/2^x*(1+sum((2/k)^8,k=3..infinity))
And sum((2/k)^8,k=3..infinity) = -257+128*Pi^8/4725 ~= 0.0438035
So Zeta(x) <= 1 + 1/2^x*2 for x >= 8
The error is < 2^(-x+1) <= 2^(-2^(EXP(x)-1)+1) */
if (MPFR_GET_EXP (s) > 3)
{
mp_exp_t err;
err = MPFR_GET_EXP (s) - 1;
if (err > (mp_exp_t) (sizeof (mp_exp_t)*CHAR_BIT-2))
err = MPFR_EMAX_MAX;
else
err = ((mp_exp_t)1) << err;
err = 1 - (-err+1); /* GET_EXP(one) - (-err+1) = err :) */
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (z, __gmpfr_one, err, 0, 1,
rnd_mode, {});
}
d = precz + MPFR_INT_CEIL_LOG2(precz) + 10;
/* we want that s1 = s-1 is exact, i.e. we should have PREC(s1) >= EXP(s) */
dint = (mpfr_uexp_t) MPFR_GET_EXP (s);
mpfr_init2 (s1, MAX (precs, dint));
inex = mpfr_sub (s1, s, __gmpfr_one, GMP_RNDN);
MPFR_ASSERTD (inex == 0);
/* case s=1 */
if (MPFR_IS_ZERO (s1))
{
MPFR_SET_INF (z);
MPFR_SET_POS (z);
MPFR_ASSERTD (inex == 0);
goto clear_and_return;
}
MPFR_GROUP_INIT_4 (group, MPFR_PREC_MIN, b, c, z_pre, f);
MPFR_ZIV_INIT (loop, d);
for (;;)
{
/* Principal loop: we compute, in z_pre,
an approximation of Zeta(s), that we send to can_round */
if (MPFR_GET_EXP (s1) <= -(mp_exp_t) ((mpfr_prec_t) (d-3)/2))
/* Branch 1: when s-1 is very small, one
uses the approximation Zeta(s)=1/(s-1)+gamma,
where gamma is Euler's constant */
{
dint = MAX (d + 3, precs);
MPFR_TRACE (printf ("branch 1\ninternal precision=%d\n", dint));
MPFR_GROUP_REPREC_4 (group, dint, b, c, z_pre, f);
mpfr_div (z_pre, __gmpfr_one, s1, GMP_RNDN);
mpfr_const_euler (f, GMP_RNDN);
mpfr_add (z_pre, z_pre, f, GMP_RNDN);
}
else /* Branch 2 */
{
size_t size;
MPFR_TRACE (printf ("branch 2\n"));
/* Computation of parameters n, p and working precision */
dnep = (double) d * LOG2;
sd = mpfr_get_d (s, GMP_RNDN);
/* beta = dnep + 0.61 + sd * log (6.2832 / sd);
but a larger value is ok */
#define LOG6dot2832 1.83787940484160805532
beta = dnep + 0.61 + sd * (LOG6dot2832 - LOG2 *
__gmpfr_floor_log2 (sd));
if (beta <= 0.0)
{
p = 0;
/* n = 1 + (int) (exp ((dnep - LOG2) / sd)); */
n = 1 + (int) __gmpfr_ceil_exp2 ((d - 1.0) / sd);
}
else
{
p = 1 + (int) beta / 2;
n = 1 + (int) ((sd + 2.0 * (double) p - 1.0) / 6.2832);
}
MPFR_TRACE (printf ("\nn=%d\np=%d\n",n,p));
/* add = 4 + floor(1.5 * log(d) / log (2)).
We should have add >= 10, which is always fulfilled since
d = precz + 11 >= 12, thus ceil(log2(d)) >= 4 */
add = 4 + (3 * MPFR_INT_CEIL_LOG2 (d)) / 2;
MPFR_ASSERTD(add >= 10);
dint = d + add;
if (dint < precs)
dint = precs;
MPFR_TRACE (printf("internal precision=%d\n",dint));
size = (p + 1) * sizeof(mpfr_t);
tc1 = (mpfr_t*) (*__gmp_allocate_func) (size);
for (l=1; l<=p; l++)
mpfr_init2 (tc1[l], dint);
MPFR_GROUP_REPREC_4 (group, dint, b, c, z_pre, f);
MPFR_TRACE (printf ("precision of z =%d\n", precz));
/* Computation of the coefficients c_k */
mpfr_zeta_c (p, tc1);
/* Computation of the 3 parts of the fonction Zeta. */
mpfr_zeta_part_a (z_pre, s, n);
mpfr_zeta_part_b (b, s, n, p, tc1);
/* s1 = s-1 is already computed above */
mpfr_div (c, __gmpfr_one, s1, GMP_RNDN);
mpfr_ui_pow (f, n, s1, GMP_RNDN);
mpfr_div (c, c, f, GMP_RNDN);
MPFR_TRACE (MPFR_DUMP (c));
mpfr_add (z_pre, z_pre, c, GMP_RNDN);
mpfr_add (z_pre, z_pre, b, GMP_RNDN);
for (l=1; l<=p; l++)
mpfr_clear (tc1[l]);
(*__gmp_free_func) (tc1, size);
/* End branch 2 */
}
MPFR_TRACE (MPFR_DUMP (z_pre));
if (MPFR_LIKELY (MPFR_CAN_ROUND (z_pre, d-3, precz, rnd_mode)))
break;
MPFR_ZIV_NEXT (loop, d);
}
MPFR_ZIV_FREE (loop);
inex = mpfr_set (z, z_pre, rnd_mode);
MPFR_GROUP_CLEAR (group);
clear_and_return:
mpfr_clear (s1);
return inex;
}
/* Compute the real part of the dilogarithm defined by
Li2(x) = -\Int_{t=0}^x log(1-t)/t dt */
int
mpfr_li2 (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
{
int inexact;
mp_exp_t err;
mpfr_prec_t yp, m;
MPFR_ZIV_DECL (loop);
MPFR_SAVE_EXPO_DECL (expo);
MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", x, x, rnd_mode), ("y[%#R]=%R", y));
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_NEG (y);
MPFR_SET_INF (y);
MPFR_RET (0);
}
else /* x is zero */
{
MPFR_ASSERTD (MPFR_IS_ZERO (x));
MPFR_SET_SAME_SIGN (y, x);
MPFR_SET_ZERO (y);
MPFR_RET (0);
}
}
/* Li2(x) = x + x^2/4 + x^3/9 + ..., more precisely for 0 < x <= 1/2
we have |Li2(x) - x| < x^2/2 <= 2^(2EXP(x)-1) and for -1/2 <= x < 0
we have |Li2(x) - x| < x^2/4 <= 2^(2EXP(x)-2) */
if (MPFR_IS_POS (x))
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, -MPFR_GET_EXP (x), 1, 1, rnd_mode,
{});
else
MPFR_FAST_COMPUTE_IF_SMALL_INPUT (y, x, -MPFR_GET_EXP (x), 2, 0, rnd_mode,
{});
MPFR_SAVE_EXPO_MARK (expo);
yp = MPFR_PREC (y);
m = yp + MPFR_INT_CEIL_LOG2 (yp) + 13;
if (MPFR_LIKELY ((mpfr_cmp_ui (x, 0) > 0) && (mpfr_cmp_d (x, 0.5) <= 0)))
/* 0 < x <= 1/2: Li2(x) = S(-log(1-x))-log^2(1-x)/4 */
{
mpfr_t s, u;
mp_exp_t expo_l;
int k;
mpfr_init2 (u, m);
mpfr_init2 (s, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_ui_sub (u, 1, x, GMP_RNDN);
mpfr_log (u, u, GMP_RNDU);
if (MPFR_IS_ZERO(u))
goto next_m;
mpfr_neg (u, u, GMP_RNDN); /* u = -log(1-x) */
expo_l = MPFR_GET_EXP (u);
k = li2_series (s, u, GMP_RNDU);
err = 1 + MPFR_INT_CEIL_LOG2 (k + 1);
mpfr_sqr (u, u, GMP_RNDU);
mpfr_div_2ui (u, u, 2, GMP_RNDU); /* u = log^2(1-x) / 4 */
mpfr_sub (s, s, u, GMP_RNDN);
/* error(s) <= (0.5 + 2^(d-EXP(s))
+ 2^(3 + MAX(1, - expo_l) - EXP(s))) ulp(s) */
err = MAX (err, MAX (1, - expo_l) - 1) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err);
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
next_m:
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (u, m);
mpfr_set_prec (s, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clear (u);
mpfr_clear (s);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else if (!mpfr_cmp_ui (x, 1))
/* Li2(1)= pi^2 / 6 */
{
mpfr_t u;
mpfr_init2 (u, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_const_pi (u, GMP_RNDU);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_ui (u, u, 6, GMP_RNDN);
err = m - 4; /* error(u) <= 19/2 ulp(u) */
if (MPFR_CAN_ROUND (u, err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (u, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, u, rnd_mode);
mpfr_clear (u);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else if (mpfr_cmp_ui (x, 2) >= 0)
/* x >= 2: Li2(x) = -S(-log(1-1/x))-log^2(x)/2+log^2(1-1/x)/4+pi^2/3 */
{
int k;
mp_exp_t expo_l;
mpfr_t s, u, xx;
if (mpfr_cmp_ui (x, 38) >= 0)
{
inexact = mpfr_li2_asympt_pos (y, x, rnd_mode);
if (inexact != 0)
goto end_of_case_gt2;
}
mpfr_init2 (u, m);
mpfr_init2 (s, m);
mpfr_init2 (xx, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_ui_div (xx, 1, x, GMP_RNDN);
mpfr_neg (xx, xx, GMP_RNDN);
mpfr_log1p (u, xx, GMP_RNDD);
mpfr_neg (u, u, GMP_RNDU); /* u = -log(1-1/x) */
expo_l = MPFR_GET_EXP (u);
k = li2_series (s, u, GMP_RNDN);
mpfr_neg (s, s, GMP_RNDN);
err = MPFR_INT_CEIL_LOG2 (k + 1) + 1; /* error(s) <= 2^err ulp(s) */
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_2ui (u, u, 2, GMP_RNDN); /* u= log^2(1-1/x)/4 */
mpfr_add (s, s, u, GMP_RNDN);
err =
MAX (err,
3 + MAX (1, -expo_l) + MPFR_GET_EXP (u)) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err); /* error(s) <= 2^err ulp(s) */
err += MPFR_GET_EXP (s);
mpfr_log (u, x, GMP_RNDU);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_2ui (u, u, 1, GMP_RNDN); /* u = log^2(x)/2 */
mpfr_sub (s, s, u, GMP_RNDN);
err = MAX (err, 3 + MPFR_GET_EXP (u)) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err); /* error(s) <= 2^err ulp(s) */
err += MPFR_GET_EXP (s);
mpfr_const_pi (u, GMP_RNDU);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_ui (u, u, 3, GMP_RNDN); /* u = pi^2/3 */
mpfr_add (s, s, u, GMP_RNDN);
err = MAX (err, 2) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err); /* error(s) <= 2^err ulp(s) */
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (u, m);
mpfr_set_prec (s, m);
mpfr_set_prec (xx, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clears (s, u, xx, (mpfr_ptr) 0);
end_of_case_gt2:
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else if (mpfr_cmp_ui (x, 1) > 0)
/* 2 > x > 1: Li2(x) = S(log(x))+log^2(x)/4-log(x)log(x-1)+pi^2/6 */
{
int k;
mp_exp_t e1, e2;
mpfr_t s, u, v, xx;
mpfr_init2 (s, m);
mpfr_init2 (u, m);
mpfr_init2 (v, m);
mpfr_init2 (xx, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_log (v, x, GMP_RNDU);
k = li2_series (s, v, GMP_RNDN);
e1 = MPFR_GET_EXP (s);
mpfr_sqr (u, v, GMP_RNDN);
mpfr_div_2ui (u, u, 2, GMP_RNDN); /* u = log^2(x)/4 */
mpfr_add (s, s, u, GMP_RNDN);
mpfr_sub_ui (xx, x, 1, GMP_RNDN);
mpfr_log (u, xx, GMP_RNDU);
e2 = MPFR_GET_EXP (u);
mpfr_mul (u, v, u, GMP_RNDN); /* u = log(x) * log(x-1) */
mpfr_sub (s, s, u, GMP_RNDN);
mpfr_const_pi (u, GMP_RNDU);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_ui (u, u, 6, GMP_RNDN); /* u = pi^2/6 */
mpfr_add (s, s, u, GMP_RNDN);
/* error(s) <= (31 + (k+1) * 2^(1-e1) + 2^(1-e2)) ulp(s)
see algorithms.tex */
err = MAX (MPFR_INT_CEIL_LOG2 (k + 1) + 1 - e1, 1 - e2);
err = 2 + MAX (5, err);
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (s, m);
mpfr_set_prec (u, m);
mpfr_set_prec (v, m);
mpfr_set_prec (xx, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clears (s, u, v, xx, (mpfr_ptr) 0);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else if (mpfr_cmp_ui_2exp (x, 1, -1) > 0) /* 1/2 < x < 1 */
/* 1 > x > 1/2: Li2(x) = -S(-log(x))+log^2(x)/4-log(x)log(1-x)+pi^2/6 */
{
int k;
mpfr_t s, u, v, xx;
mpfr_init2 (s, m);
mpfr_init2 (u, m);
mpfr_init2 (v, m);
mpfr_init2 (xx, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_log (u, x, GMP_RNDD);
mpfr_neg (u, u, GMP_RNDN);
k = li2_series (s, u, GMP_RNDN);
mpfr_neg (s, s, GMP_RNDN);
err = 1 + MPFR_INT_CEIL_LOG2 (k + 1) - MPFR_GET_EXP (s);
mpfr_ui_sub (xx, 1, x, GMP_RNDN);
mpfr_log (v, xx, GMP_RNDU);
mpfr_mul (v, v, u, GMP_RNDN); /* v = - log(x) * log(1-x) */
mpfr_add (s, s, v, GMP_RNDN);
err = MAX (err, 1 - MPFR_GET_EXP (v));
err = 2 + MAX (3, err) - MPFR_GET_EXP (s);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_2ui (u, u, 2, GMP_RNDN); /* u = log^2(x)/4 */
mpfr_add (s, s, u, GMP_RNDN);
err = MAX (err, 2 + MPFR_GET_EXP (u)) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err) + MPFR_GET_EXP (s);
mpfr_const_pi (u, GMP_RNDU);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_ui (u, u, 6, GMP_RNDN); /* u = pi^2/6 */
mpfr_add (s, s, u, GMP_RNDN);
err = MAX (err, 3) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err);
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (s, m);
mpfr_set_prec (u, m);
mpfr_set_prec (v, m);
mpfr_set_prec (xx, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clears (s, u, v, xx, (mpfr_ptr) 0);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else if (mpfr_cmp_si (x, -1) >= 0)
/* 0 > x >= -1: Li2(x) = -S(log(1-x))-log^2(1-x)/4 */
{
int k;
mp_exp_t expo_l;
mpfr_t s, u, xx;
mpfr_init2 (s, m);
mpfr_init2 (u, m);
mpfr_init2 (xx, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_neg (xx, x, GMP_RNDN);
mpfr_log1p (u, xx, GMP_RNDN);
k = li2_series (s, u, GMP_RNDN);
mpfr_neg (s, s, GMP_RNDN);
expo_l = MPFR_GET_EXP (u);
err = 1 + MPFR_INT_CEIL_LOG2 (k + 1) - MPFR_GET_EXP (s);
mpfr_sqr (u, u, GMP_RNDN);
mpfr_div_2ui (u, u, 2, GMP_RNDN); /* u = log^2(1-x)/4 */
mpfr_sub (s, s, u, GMP_RNDN);
err = MAX (err, - expo_l);
err = 2 + MAX (err, 3);
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (s, m);
mpfr_set_prec (u, m);
mpfr_set_prec (xx, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clears (s, u, xx, (mpfr_ptr) 0);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
else
/* x < -1: Li2(x)
= S(log(1-1/x))-log^2(-x)/4-log(1-x)log(-x)/2+log^2(1-x)/4-pi^2/6 */
{
int k;
mpfr_t s, u, v, w, xx;
if (mpfr_cmp_si (x, -7) <= 0)
{
inexact = mpfr_li2_asympt_neg (y, x, rnd_mode);
if (inexact != 0)
goto end_of_case_ltm1;
}
mpfr_init2 (s, m);
mpfr_init2 (u, m);
mpfr_init2 (v, m);
mpfr_init2 (w, m);
mpfr_init2 (xx, m);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
mpfr_ui_div (xx, 1, x, GMP_RNDN);
mpfr_neg (xx, xx, GMP_RNDN);
mpfr_log1p (u, xx, GMP_RNDN);
k = li2_series (s, u, GMP_RNDN);
mpfr_ui_sub (xx, 1, x, GMP_RNDN);
mpfr_log (u, xx, GMP_RNDU);
mpfr_neg (xx, x, GMP_RNDN);
mpfr_log (v, xx, GMP_RNDU);
mpfr_mul (w, v, u, GMP_RNDN);
mpfr_div_2ui (w, w, 1, GMP_RNDN); /* w = log(-x) * log(1-x) / 2 */
mpfr_sub (s, s, w, GMP_RNDN);
err = 1 + MAX (3, MPFR_INT_CEIL_LOG2 (k+1) + 1 - MPFR_GET_EXP (s))
+ MPFR_GET_EXP (s);
mpfr_sqr (w, v, GMP_RNDN);
mpfr_div_2ui (w, w, 2, GMP_RNDN); /* w = log^2(-x) / 4 */
mpfr_sub (s, s, w, GMP_RNDN);
err = MAX (err, 3 + MPFR_GET_EXP(w)) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err) + MPFR_GET_EXP (s);
mpfr_sqr (w, u, GMP_RNDN);
mpfr_div_2ui (w, w, 2, GMP_RNDN); /* w = log^2(1-x) / 4 */
mpfr_add (s, s, w, GMP_RNDN);
err = MAX (err, 3 + MPFR_GET_EXP (w)) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err) + MPFR_GET_EXP (s);
mpfr_const_pi (w, GMP_RNDU);
mpfr_sqr (w, w, GMP_RNDN);
mpfr_div_ui (w, w, 6, GMP_RNDN); /* w = pi^2 / 6 */
mpfr_sub (s, s, w, GMP_RNDN);
err = MAX (err, 3) - MPFR_GET_EXP (s);
err = 2 + MAX (-1, err) + MPFR_GET_EXP (s);
if (MPFR_CAN_ROUND (s, (mp_exp_t) m - err, yp, rnd_mode))
break;
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (s, m);
mpfr_set_prec (u, m);
mpfr_set_prec (v, m);
mpfr_set_prec (w, m);
mpfr_set_prec (xx, m);
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
mpfr_clears (s, u, v, w, xx, (mpfr_ptr) 0);
end_of_case_ltm1:
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (y, inexact, rnd_mode);
}
MPFR_ASSERTN (0); /* should never reach this point */
}
