static void
bug20090227 (void)
{
mpfr_t x, y, r1, r2;
int inex1, inex2;
mpfr_init2 (x, 118);
mpfr_init2 (y, 181);
mpfr_init2 (r1, 140);
mpfr_init2 (r2, 140);
mpfr_set_si (x, -1, MPFR_RNDN);
mpfr_set_str_binary (y, "1.100100100001111110110101010001000100001011010001100001000110100110001001100011001100010100010111000000011011100000111001101000100101001000000100100111000001000100010100110011111010");
inex1 = mpfr_remainder (r1, x, y, MPFR_RNDU);
/* since the quotient is -1, r1 is the rounding of x+y */
inex2 = mpfr_add (r2, x, y, MPFR_RNDU);
if (mpfr_cmp (r1, r2))
{
printf ("Error in mpfr_remainder (bug20090227)\n");
printf ("Expected ");
mpfr_dump (r2);
printf ("Got ");
mpfr_dump (r1);
exit (1);
}
mpfr_clear (x);
mpfr_clear (y);
mpfr_clear (r1);
mpfr_clear (r2);
}
real remainder(const real & a, const real & b)
{
real x;
mpfr_remainder(x.r, a.r, b.r, MPFR_RNDN);
return x;
}
SeedValue seed_mpfr_remainder (SeedContext ctx,
SeedObject function,
SeedObject this_object,
gsize argument_count,
const SeedValue args[],
SeedException *exception)
{
mpfr_rnd_t rnd;
mpfr_ptr rop, op1, op2;
gint ret;
CHECK_ARG_COUNT("mpfr.remainder", 3);
rop = seed_object_get_private(this_object);
rnd = seed_value_to_mpfr_rnd_t(ctx, args[2], exception);
if ( seed_value_is_object_of_class(ctx, args[0], mpfr_class) &&
seed_value_is_object_of_class(ctx, args[1], mpfr_class))
{
op1 = seed_object_get_private(args[0]);
op2 = seed_object_get_private(args[1]);
}
else
{
TYPE_EXCEPTION("mpfr.remainder", "mpfr_t");
}
ret = mpfr_remainder(rop, op1, op2, rnd);
return seed_value_from_int(ctx, ret, exception);
}
int
main (int argc, char *argv[])
{
mpfr_t x, y, r;
long q[1];
if (argc == 3) /* usage: tremquo x y (rnd=MPFR_RNDN implicit) */
{
mpfr_init2 (x, GMP_NUMB_BITS);
mpfr_init2 (y, GMP_NUMB_BITS);
mpfr_init2 (r, GMP_NUMB_BITS);
mpfr_set_str (x, argv[1], 10, MPFR_RNDN);
mpfr_set_str (y, argv[2], 10, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
printf ("r=");
mpfr_out_str (stdout, 10, 0, r, MPFR_RNDN);
printf (" q=%ld\n", q[0]);
mpfr_clear (x);
mpfr_clear (y);
mpfr_clear (r);
return 0;
}
tests_start_mpfr ();
bug20090227 ();
mpfr_init (x);
mpfr_init (y);
mpfr_init (r);
/* special values */
mpfr_set_nan (x);
mpfr_set_ui (y, 1, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN(mpfr_nan_p (r));
mpfr_set_ui (x, 1, MPFR_RNDN);
mpfr_set_nan (y);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN(mpfr_nan_p (r));
mpfr_set_inf (x, 1); /* +Inf */
mpfr_set_ui (y, 1, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_nan_p (r));
mpfr_set_inf (x, 1); /* +Inf */
mpfr_set_ui (y, 0, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_nan_p (r));
mpfr_set_inf (x, 1); /* +Inf */
mpfr_set_inf (y, 1);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_nan_p (r));
mpfr_set_ui (x, 0, MPFR_RNDN);
mpfr_set_inf (y, 1);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 0) == 0 && MPFR_IS_POS (r));
MPFR_ASSERTN (q[0] == (long) 0);
mpfr_set_ui (x, 0, MPFR_RNDN);
mpfr_neg (x, x, MPFR_RNDN); /* -0 */
mpfr_set_inf (y, 1);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 0) == 0 && MPFR_IS_NEG (r));
MPFR_ASSERTN (q[0] == (long) 0);
mpfr_set_ui (x, 17, MPFR_RNDN);
mpfr_set_inf (y, 1);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp (r, x) == 0);
MPFR_ASSERTN (q[0] == (long) 0);
mpfr_set_ui (x, 17, MPFR_RNDN);
mpfr_set_ui (y, 0, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_nan_p (r));
mpfr_set_ui (x, 0, MPFR_RNDN);
mpfr_set_ui (y, 17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 0) == 0 && MPFR_IS_POS (r));
MPFR_ASSERTN (q[0] == (long) 0);
mpfr_set_ui (x, 0, MPFR_RNDN);
mpfr_neg (x, x, MPFR_RNDN);
mpfr_set_ui (y, 17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 0) == 0 && MPFR_IS_NEG (r));
MPFR_ASSERTN (q[0] == (long) 0);
mpfr_set_prec (x, 53);
mpfr_set_prec (y, 53);
/* check four possible sign combinations */
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_set_ui (y, 17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 8) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
mpfr_set_si (x, -42, MPFR_RNDN);
mpfr_set_ui (y, 17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (r, -8) == 0);
MPFR_ASSERTN (q[0] == (long) -2);
mpfr_set_si (x, -42, MPFR_RNDN);
mpfr_set_si (y, -17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (r, -8) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_set_si (y, -17, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui (r, 8) == 0);
MPFR_ASSERTN (q[0] == (long) -2);
mpfr_set_prec (x, 100);
mpfr_set_prec (y, 50);
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_nextabove (x); /* 42 + 2^(-94) */
mpfr_set_ui (y, 21, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui_2exp (r, 1, -94) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
mpfr_set_prec (x, 50);
mpfr_set_prec (y, 100);
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_nextabove (x); /* 42 + 2^(-44) */
mpfr_set_ui (y, 21, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_ui_2exp (r, 1, -44) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
mpfr_set_prec (x, 100);
mpfr_set_prec (y, 50);
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_set_ui (y, 21, MPFR_RNDN);
mpfr_nextabove (y); /* 21 + 2^(-45) */
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* r should be 42 - 2*(21 + 2^(-45)) = -2^(-44) */
MPFR_ASSERTN (mpfr_cmp_si_2exp (r, -1, -44) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
mpfr_set_prec (x, 50);
mpfr_set_prec (y, 100);
mpfr_set_ui (x, 42, MPFR_RNDN);
mpfr_set_ui (y, 21, MPFR_RNDN);
mpfr_nextabove (y); /* 21 + 2^(-95) */
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* r should be 42 - 2*(21 + 2^(-95)) = -2^(-94) */
MPFR_ASSERTN (mpfr_cmp_si_2exp (r, -1, -94) == 0);
MPFR_ASSERTN (q[0] == (long) 2);
/* exercise large quotient */
mpfr_set_ui_2exp (x, 1, 65, MPFR_RNDN);
mpfr_set_ui (y, 1, MPFR_RNDN);
/* quotient is 2^65 */
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (r, 0) == 0);
MPFR_ASSERTN (q[0] % 1073741824L == 0L);
/* another large quotient */
mpfr_set_prec (x, 65);
mpfr_set_prec (y, 65);
mpfr_const_pi (x, MPFR_RNDN);
mpfr_mul_2exp (x, x, 63, MPFR_RNDN);
mpfr_const_log2 (y, MPFR_RNDN);
mpfr_set_prec (r, 10);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* q should be 41803643793084085130, r should be 605/2048 */
MPFR_ASSERTN (mpfr_cmp_ui_2exp (r, 605, -11) == 0);
MPFR_ASSERTN ((q[0] > 0) && ((q[0] % 1073741824L) == 733836170L));
/* check cases where quotient is 1.5 +/- eps */
mpfr_set_prec (x, 65);
mpfr_set_prec (y, 65);
mpfr_set_prec (r, 63);
mpfr_set_ui (x, 3, MPFR_RNDN);
mpfr_set_ui (y, 2, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* x/y = 1.5, quotient should be 2 (even rule), remainder should be -1 */
MPFR_ASSERTN (mpfr_cmp_si (r, -1) == 0);
MPFR_ASSERTN (q[0] == 2L);
mpfr_set_ui (x, 3, MPFR_RNDN);
mpfr_nextabove (x); /* 3 + 2^(-63) */
mpfr_set_ui (y, 2, MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* x/y = 1.5 + 2^(-64), quo should be 2, r should be -1 + 2^(-63) */
MPFR_ASSERTN (mpfr_add_ui (r, r, 1, MPFR_RNDN) == 0);
MPFR_ASSERTN (mpfr_cmp_ui_2exp (r, 1, -63) == 0);
MPFR_ASSERTN (q[0] == 2L);
mpfr_set_ui (x, 3, MPFR_RNDN);
mpfr_set_ui (y, 2, MPFR_RNDN);
mpfr_nextabove (y); /* 2 + 2^(-63) */
mpfr_remquo (r, q, x, y, MPFR_RNDN);
/* x/y = 1.5 - eps, quo should be 1, r should be 1 - 2^(-63) */
MPFR_ASSERTN (mpfr_sub_ui (r, r, 1, MPFR_RNDN) == 0);
MPFR_ASSERTN (mpfr_cmp_si_2exp (r, -1, -63) == 0);
MPFR_ASSERTN (q[0] == 1L);
/* bug founds by Kaveh Ghazi, 3 May 2007 */
mpfr_set_ui (x, 2, MPFR_RNDN);
mpfr_set_ui (y, 3, MPFR_RNDN);
mpfr_remainder (r, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (r, -1) == 0);
mpfr_set_si (x, -1, MPFR_RNDN);
mpfr_set_ui (y, 1, MPFR_RNDN);
mpfr_remainder (r, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (r, 0) == 0 && MPFR_SIGN (r) < 0);
/* check argument reuse */
mpfr_set_si (x, -1, MPFR_RNDN);
mpfr_set_ui (y, 1, MPFR_RNDN);
mpfr_remainder (x, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_cmp_si (x, 0) == 0 && MPFR_SIGN (x) < 0);
mpfr_set_ui_2exp (x, 1, mpfr_get_emax () - 1, MPFR_RNDN);
mpfr_set_ui_2exp (y, 1, mpfr_get_emin (), MPFR_RNDN);
mpfr_remquo (r, q, x, y, MPFR_RNDN);
MPFR_ASSERTN (mpfr_zero_p (r) && MPFR_SIGN (r) > 0);
MPFR_ASSERTN (q[0] == 0);
mpfr_clear (x);
mpfr_clear (y);
mpfr_clear (r);
tests_end_mpfr ();
return 0;
}
/* (y, z) <- (sin(x), cos(x)), return value is 0 iff both results are exact
ie, iff x = 0 */
int
mpfr_sin_cos (mpfr_ptr y, mpfr_ptr z, mpfr_srcptr x, mp_rnd_t rnd_mode)
{
mp_prec_t prec, m;
int neg, reduce;
mpfr_t c, xr;
mpfr_srcptr xx;
mp_exp_t err, expx;
MPFR_ZIV_DECL (loop);
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
{
if (MPFR_IS_NAN(x) || MPFR_IS_INF(x))
{
MPFR_SET_NAN (y);
MPFR_SET_NAN (z);
MPFR_RET_NAN;
}
else /* x is zero */
{
MPFR_ASSERTD (MPFR_IS_ZERO (x));
MPFR_SET_ZERO (y);
MPFR_SET_SAME_SIGN (y, x);
/* y = 0, thus exact, but z is inexact in case of underflow
or overflow */
return mpfr_set_ui (z, 1, rnd_mode);
}
}
MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", x, x, rnd_mode),
("sin[%#R]=%R cos[%#R]=%R", y, y, z, z));
prec = MAX (MPFR_PREC (y), MPFR_PREC (z));
m = prec + MPFR_INT_CEIL_LOG2 (prec) + 13;
expx = MPFR_GET_EXP (x);
mpfr_init (c);
mpfr_init (xr);
MPFR_ZIV_INIT (loop, m);
for (;;)
{
/* the following is copied from sin.c */
if (expx >= 2) /* reduce the argument */
{
reduce = 1;
mpfr_set_prec (c, expx + m - 1);
mpfr_set_prec (xr, m);
mpfr_const_pi (c, GMP_RNDN);
mpfr_mul_2ui (c, c, 1, GMP_RNDN);
mpfr_remainder (xr, x, c, GMP_RNDN);
mpfr_div_2ui (c, c, 1, GMP_RNDN);
if (MPFR_SIGN (xr) > 0)
mpfr_sub (c, c, xr, GMP_RNDZ);
else
mpfr_add (c, c, xr, GMP_RNDZ);
if (MPFR_IS_ZERO(xr) || MPFR_EXP(xr) < (mp_exp_t) 3 - (mp_exp_t) m
|| MPFR_EXP(c) < (mp_exp_t) 3 - (mp_exp_t) m)
goto next_step;
xx = xr;
}
else /* the input argument is already reduced */
{
reduce = 0;
xx = x;
}
neg = MPFR_IS_NEG (xx); /* gives sign of sin(x) */
mpfr_set_prec (c, m);
mpfr_cos (c, xx, GMP_RNDZ);
/* If no argument reduction was performed, the error is at most ulp(c),
otherwise it is at most ulp(c) + 2^(2-m). Since |c| < 1, we have
ulp(c) <= 2^(-m), thus the error is bounded by 2^(3-m) in that later
case. */
if (reduce == 0)
err = m;
else
err = MPFR_GET_EXP (c) + (mp_exp_t) (m - 3);
if (!mpfr_can_round (c, err, GMP_RNDN, rnd_mode,
MPFR_PREC (z) + (rnd_mode == GMP_RNDN)))
goto next_step;
mpfr_set (z, c, rnd_mode);
mpfr_sqr (c, c, GMP_RNDU);
mpfr_ui_sub (c, 1, c, GMP_RNDN);
err = 2 + (- MPFR_GET_EXP (c)) / 2;
mpfr_sqrt (c, c, GMP_RNDN);
if (neg)
MPFR_CHANGE_SIGN (c);
/* the absolute error on c is at most 2^(err-m), which we must put
in the form 2^(EXP(c)-err). If there was an argument reduction,
we need to add 2^(2-m); since err >= 2, the error is bounded by
2^(err+1-m) in that case. */
err = MPFR_GET_EXP (c) + (mp_exp_t) m - (err + reduce);
if (mpfr_can_round (c, err, GMP_RNDN, rnd_mode,
MPFR_PREC (y) + (rnd_mode == GMP_RNDN)))
break;
/* check for huge cancellation */
if (err < (mp_exp_t) MPFR_PREC (y))
m += MPFR_PREC (y) - err;
/* Check if near 1 */
if (MPFR_GET_EXP (c) == 1
&& MPFR_MANT (c)[MPFR_LIMB_SIZE (c)-1] == MPFR_LIMB_HIGHBIT)
m += m;
next_step:
MPFR_ZIV_NEXT (loop, m);
mpfr_set_prec (c, m);
}
MPFR_ZIV_FREE (loop);
mpfr_set (y, c, rnd_mode);
mpfr_clear (c);
mpfr_clear (xr);
MPFR_RET (1); /* Always inexact */
}
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);
for (k = 0; k < K; k++)
{
mpfr_sqr (s, s, MPFR_RNDU); /* err <= 2*olderr */
MPFR_SET_EXP (s, MPFR_GET_EXP (s) + 1); /* Can't overflow */
mpfr_sub (s, s, r, MPFR_RNDN); /* err <= 4*olderr */
if (MPFR_IS_ZERO(s))
goto ziv_next;
MPFR_ASSERTD (MPFR_GET_EXP (s) <= 1);
}
/* The absolute error on s is bounded by (2l+1/3)*2^(2K-m)
2l+1/3 <= 2l+1.
If |x| >= 4, we need to add 2^(2-m) for the argument reduction
by 2Pi: if K = 0, this amounts to add 4 to 2l+1/3, i.e., to add
2 to l; if K >= 1, this amounts to add 1 to 2*l+1/3. */
l = 2 * l + 1;
if (reduce)
l += (K == 0) ? 4 : 1;
k = MPFR_INT_CEIL_LOG2 (l) + 2*K;
/* now the error is bounded by 2^(k-m) = 2^(EXP(s)-err) */
exps = MPFR_GET_EXP (s);
if (MPFR_LIKELY (MPFR_CAN_ROUND (s, exps + m - k, precy, rnd_mode)))
break;
if (MPFR_UNLIKELY (exps == 1))
/* s = 1 or -1, and except x=0 which was already checked above,
cos(x) cannot be 1 or -1, so we can round if the error is less
than 2^(-precy) for directed rounding, or 2^(-precy-1) for rounding
to nearest. */
{
if (m > k && (m - k >= precy + (rnd_mode == MPFR_RNDN)))
{
/* If round to nearest or away, result is s = 1 or -1,
otherwise it is round(nexttoward (s, 0)). However in order to
have the inexact flag correctly set below, we set |s| to
1 - 2^(-m) in all cases. */
mpfr_nexttozero (s);
break;
}
}
if (exps < cancel)
{
m += cancel - exps;
cancel = exps;
}
ziv_next:
MPFR_ZIV_NEXT (loop, m);
MPFR_GROUP_REPREC_2 (group, m, r, s);
if (reduce)
{
mpfr_set_prec (xr, m);
mpfr_set_prec (c, expx + m - 1);
}
}
MPFR_ZIV_FREE (loop);
inexact = mpfr_set (y, s, rnd_mode);
MPFR_GROUP_CLEAR (group);
if (reduce)
{
mpfr_clear (xr);
mpfr_clear (c);
}
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);
}
