1 /* mpfr_set_q -- set a floating-point number from a multiple-precision rational 2 3 Copyright 2000-2002, 2004-2023 Free Software Foundation, Inc. 4 Contributed by the AriC and Caramba projects, INRIA. 5 6 This file is part of the GNU MPFR Library. 7 8 The GNU MPFR Library is free software; you can redistribute it and/or modify 9 it under the terms of the GNU Lesser General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or (at your 11 option) any later version. 12 13 The GNU MPFR Library is distributed in the hope that it will be useful, but 14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16 License for more details. 17 18 You should have received a copy of the GNU Lesser General Public License 19 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 20 https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23 #define MPFR_NEED_LONGLONG_H 24 #include "mpfr-impl.h" 25 26 #ifndef MPFR_USE_MINI_GMP 27 /* 28 * Set f to z, choosing the smallest precision for f 29 * so that z = f*(2^BPML)*zs*2^(RetVal) 30 */ 31 static int 32 set_z (mpfr_ptr f, mpz_srcptr z, mp_size_t *zs) 33 { 34 mp_limb_t *p; 35 mp_size_t s; 36 int c; 37 mpfr_prec_t pf; 38 39 MPFR_ASSERTD (mpz_sgn (z) != 0); 40 41 /* Remove useless ending 0 */ 42 for (p = PTR (z), s = *zs = ABSIZ (z) ; *p == 0; p++, s--) 43 MPFR_ASSERTD (s >= 0); 44 45 /* Get working precision */ 46 count_leading_zeros (c, p[s-1]); 47 pf = s * GMP_NUMB_BITS - c; 48 MPFR_ASSERTD (pf >= 1); 49 mpfr_init2 (f, pf >= MPFR_PREC_MIN ? pf : MPFR_PREC_MIN); 50 51 /* Copy Mantissa */ 52 if (MPFR_LIKELY (c)) 53 mpn_lshift (MPFR_MANT (f), p, s, c); 54 else 55 MPN_COPY (MPFR_MANT (f), p, s); 56 57 MPFR_SET_SIGN (f, mpz_sgn (z)); 58 MPFR_SET_EXP (f, 0); 59 60 return -c; 61 } 62 63 /* set f to the rational q */ 64 int 65 mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mpfr_rnd_t rnd) 66 { 67 mpz_srcptr num, den; 68 mpfr_t n, d; 69 int inexact; 70 int cn, cd; 71 long shift; 72 mp_size_t sn, sd; 73 MPFR_SAVE_EXPO_DECL (expo); 74 75 num = mpq_numref (q); 76 den = mpq_denref (q); 77 /* NAN and INF for mpq are not really documented, but could be found */ 78 if (MPFR_UNLIKELY (mpz_sgn (num) == 0)) 79 { 80 if (MPFR_UNLIKELY (mpz_sgn (den) == 0)) 81 { 82 MPFR_SET_NAN (f); 83 MPFR_RET_NAN; 84 } 85 else 86 { 87 MPFR_SET_ZERO (f); 88 MPFR_SET_POS (f); 89 MPFR_RET (0); 90 } 91 } 92 if (MPFR_UNLIKELY (mpz_sgn (den) == 0)) 93 { 94 MPFR_SET_INF (f); 95 MPFR_SET_SIGN (f, mpz_sgn (num)); 96 MPFR_RET (0); 97 } 98 99 MPFR_SAVE_EXPO_MARK (expo); 100 101 cn = set_z (n, num, &sn); 102 cd = set_z (d, den, &sd); 103 104 /* sn is the number of limbs of the numerator, sd that of the denominator */ 105 106 sn -= sd; 107 #if GMP_NUMB_BITS <= 32 /* overflow/underflow cannot happen on 64-bit 108 processors, where MPFR_EMAX_MAX is 2^62 - 1, due to 109 memory limits */ 110 /* If sn >= 0, the quotient has at most sn limbs, thus is larger or equal to 111 2^((sn-1)*GMP_NUMB_BITS), thus its exponent >= (sn-1)*GMP_NUMB_BITS)+1. 112 (sn-1)*GMP_NUMB_BITS)+1 > emax yields (sn-1)*GMP_NUMB_BITS) >= emax, 113 i.e., sn-1 >= floor(emax/GMP_NUMB_BITS). */ 114 if (MPFR_UNLIKELY (sn > MPFR_EMAX_MAX / GMP_NUMB_BITS)) 115 { 116 MPFR_SAVE_EXPO_FREE (expo); 117 inexact = mpfr_overflow (f, rnd, MPFR_SIGN (f)); 118 goto end; 119 } 120 /* If sn < 0, the inverse quotient is >= 2^((-sn-1)*GMP_NUMB_BITS), 121 thus the quotient is <= 2^((sn+1)*GMP_NUMB_BITS), and thus its 122 exponent is <= (sn+1)*GMP_NUMB_BITS+1. 123 (sn+1)*GMP_NUMB_BITS+1 < emin yields (sn+1)*GMP_NUMB_BITS+2 <= emin, 124 i.e., sn+1 <= floor((emin-2)/GMP_NUMB_BITS). */ 125 if (MPFR_UNLIKELY (sn <= (MPFR_EMIN_MIN - 2) / GMP_NUMB_BITS - 1)) 126 { 127 MPFR_SAVE_EXPO_FREE (expo); 128 if (rnd == MPFR_RNDN) 129 rnd = MPFR_RNDZ; 130 inexact = mpfr_underflow (f, rnd, MPFR_SIGN (f)); 131 goto end; 132 } 133 #endif 134 135 inexact = mpfr_div (f, n, d, rnd); 136 shift = GMP_NUMB_BITS*sn+cn-cd; 137 MPFR_ASSERTD (shift == GMP_NUMB_BITS*sn+cn-cd); 138 cd = mpfr_mul_2si (f, f, shift, rnd); 139 MPFR_SAVE_EXPO_FREE (expo); 140 /* we can have cd <> 0 only in case of underflow or overflow, but since we 141 are still in extended exponent range, this cannot happen on 64-bit (see 142 above) */ 143 #if GMP_NUMB_BITS <= 32 144 if (MPFR_UNLIKELY (cd != 0)) 145 inexact = cd; 146 else 147 inexact = mpfr_check_range (f, inexact, rnd); 148 end: 149 #else 150 MPFR_ASSERTD(cd == 0); 151 inexact = mpfr_check_range (f, inexact, rnd); 152 #endif 153 mpfr_clear (d); 154 mpfr_clear (n); 155 MPFR_RET (inexact); 156 } 157 #endif 158