source/libs/gmp/gmp-src/mpq/cmp.c

   1 /* mpq_cmp(u,v) -- Compare U, V.  Return positive, zero, or negative
   2    based on if U > V, U == V, or U < V.
   3
   4 Copyright 1991, 1994, 1996, 2001, 2002, 2005, 2015 Free Software Foundation, Inc.
   5
   6 This file is part of the GNU MP Library.
   7
   8 The GNU MP Library is free software; you can redistribute it and/or modify
   9 it under the terms of either:
  10
  11   * the GNU Lesser General Public License as published by the Free
  12     Software Foundation; either version 3 of the License, or (at your
  13     option) any later version.
  14
  15 or
  16
  17   * the GNU General Public License as published by the Free Software
  18     Foundation; either version 2 of the License, or (at your option) any
  19     later version.
  20
  21 or both in parallel, as here.
  22
  23 The GNU MP Library is distributed in the hope that it will be useful, but
  24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  25 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  26 for more details.
  27
  28 You should have received copies of the GNU General Public License and the
  29 GNU Lesser General Public License along with the GNU MP Library.  If not,
  30 see https://www.gnu.org/licenses/.  */
  31
  32 #include "gmp.h"
  33 #include "gmp-impl.h"
  34 #include "longlong.h"
  35
  36 static int
  37 mpq_cmp_numden (mpq_srcptr op1, mpz_srcptr num_op2, mpz_srcptr den_op2)
  38 {
  39   mp_size_t num1_size = SIZ(NUM(op1));
  40   mp_size_t den1_size = SIZ(DEN(op1));
  41   mp_size_t num2_size = SIZ(num_op2);
  42   mp_size_t den2_size = SIZ(den_op2);
  43   int op2_is_int;
  44   mp_limb_t d1h, d2h;
  45   mp_size_t tmp1_size, tmp2_size;
  46   mp_ptr tmp1_ptr, tmp2_ptr;
  47   mp_size_t num1_sign;
  48   int cc;
  49   TMP_DECL;
  50
  51   /* need canonical signs to get right result */
  52   ASSERT (den1_size > 0);
  53   ASSERT (den2_size > 0);
  54
  55   if (num1_size == 0)
  56     return -num2_size;
  57   if (num2_size == 0)
  58     return num1_size;
  59   if ((num1_size ^ num2_size) < 0) /* I.e. are the signs different? */
  60     return num1_size;
  61
  62   num1_sign = num1_size;
  63   num1_size = ABS (num1_size);
  64
  65   /* THINK: Does storing d1h and d2h make sense? */
  66   d1h = PTR(DEN(op1))[den1_size - 1];
  67   d2h = PTR(den_op2)[den2_size - 1];
  68   op2_is_int = (den2_size | d2h) == 1;
  69   if (op2_is_int == (den1_size | d1h)) /* Both ops are integers */
  70     /* return mpz_cmp (NUM (op1), num_op2); */
  71     {
  72       int cmp;
  73
  74       if (num1_sign != num2_size)
  75         return num1_sign - num2_size;
  76
  77       cmp = mpn_cmp (PTR(NUM(op1)), PTR(num_op2), num1_size);
  78       return (num1_sign > 0 ? cmp : -cmp);
  79     }
  80
  81   num2_size = ABS (num2_size);
  82
  83   tmp1_size = num1_size + den2_size;
  84   tmp2_size = num2_size + den1_size;
  85
  86   /* 1. Check to see if we can tell which operand is larger by just looking at
  87      the number of limbs.  */
  88
  89   /* NUM1 x DEN2 is either TMP1_SIZE limbs or TMP1_SIZE-1 limbs.
  90      Same for NUM1 x DEN1 with respect to TMP2_SIZE.  */
  91   if (tmp1_size > tmp2_size + 1)
  92     /* NUM1 x DEN2 is surely larger in magnitude than NUM2 x DEN1.  */
  93     return num1_sign;
  94   if (tmp2_size + op2_is_int > tmp1_size + 1)
  95     /* NUM1 x DEN2 is surely smaller in magnitude than NUM2 x DEN1.  */
  96     return -num1_sign;
  97
  98   /* 2. Same, but compare the number of significant bits.  */
  99   {
 100     int cnt1, cnt2;
 101     mp_bitcnt_t bits1, bits2;
 102
 103     count_leading_zeros (cnt1, PTR(NUM(op1))[num1_size - 1]);
 104     count_leading_zeros (cnt2, d2h);
 105     bits1 = (mp_bitcnt_t) tmp1_size * GMP_NUMB_BITS - cnt1 - cnt2 + 2 * GMP_NAIL_BITS;
 106
 107     count_leading_zeros (cnt1, PTR(num_op2)[num2_size - 1]);
 108     count_leading_zeros (cnt2, d1h);
 109     bits2 = (mp_bitcnt_t) tmp2_size * GMP_NUMB_BITS - cnt1 - cnt2 + 2 * GMP_NAIL_BITS;
 110
 111     if (bits1 > bits2 + 1)
 112       return num1_sign;
 113     if (bits2 + op2_is_int > bits1 + 1)
 114       return -num1_sign;
 115   }
 116
 117   /* 3. Finally, cross multiply and compare.  */
 118
 119   TMP_MARK;
 120   if (op2_is_int)
 121     {
 122       tmp2_ptr = TMP_ALLOC_LIMBS (tmp2_size);
 123       tmp1_ptr = PTR(NUM(op1));
 124       --tmp1_size;
 125     }
 126   else
 127     {
 128   TMP_ALLOC_LIMBS_2 (tmp1_ptr,tmp1_size, tmp2_ptr,tmp2_size);
 129
 130   if (num1_size >= den2_size)
 131     tmp1_size -= 0 == mpn_mul (tmp1_ptr,
 132                                PTR(NUM(op1)), num1_size,
 133                                PTR(den_op2), den2_size);
 134   else
 135     tmp1_size -= 0 == mpn_mul (tmp1_ptr,
 136                                PTR(den_op2), den2_size,
 137                                PTR(NUM(op1)), num1_size);
 138     }
 139
 140    if (num2_size >= den1_size)
 141      tmp2_size -= 0 == mpn_mul (tmp2_ptr,
 142                                 PTR(num_op2), num2_size,
 143                                 PTR(DEN(op1)), den1_size);
 144    else
 145      tmp2_size -= 0 == mpn_mul (tmp2_ptr,
 146                                 PTR(DEN(op1)), den1_size,
 147                                 PTR(num_op2), num2_size);
 148
 149
 150   cc = tmp1_size - tmp2_size != 0
 151     ? tmp1_size - tmp2_size : mpn_cmp (tmp1_ptr, tmp2_ptr, tmp1_size);
 152   TMP_FREE;
 153   return num1_sign < 0 ? -cc : cc;
 154 }
 155
 156 int
 157 mpq_cmp (mpq_srcptr op1, mpq_srcptr op2)
 158 {
 159   return mpq_cmp_numden (op1, NUM(op2), DEN(op2));
 160 }
 161
 162 int
 163 mpq_cmp_z (mpq_srcptr op1, mpz_srcptr op2)
 164 {
 165   const static mp_limb_t one = 1;
 166   const static mpz_t den = MPZ_ROINIT_N ((mp_limb_t *) &one, 1);
 167
 168   return mpq_cmp_numden (op1, op2, den);
 169 }