cmp.c
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上传日期:2022-08-06
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- /* mpq_cmp(u,v) -- Compare U, V. Return positive, zero, or negative
- based on if U > V, U == V, or U < V.
- Copyright 1991, 1994, 1996, 2001, 2002, 2005 Free Software Foundation, Inc.
- This file is part of the GNU MP Library.
- The GNU MP Library is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 3 of the License, or (at your
- option) any later version.
- The GNU MP Library is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- #include "longlong.h"
- int
- mpq_cmp (const MP_RAT *op1, const MP_RAT *op2)
- {
- mp_size_t num1_size = op1->_mp_num._mp_size;
- mp_size_t den1_size = op1->_mp_den._mp_size;
- mp_size_t num2_size = op2->_mp_num._mp_size;
- mp_size_t den2_size = op2->_mp_den._mp_size;
- mp_size_t tmp1_size, tmp2_size;
- mp_ptr tmp1_ptr, tmp2_ptr;
- mp_size_t num1_sign;
- int cc;
- TMP_DECL;
- /* need canonical signs to get right result */
- ASSERT (den1_size > 0);
- ASSERT (den2_size > 0);
- if (num1_size == 0)
- return -num2_size;
- if (num2_size == 0)
- return num1_size;
- if ((num1_size ^ num2_size) < 0) /* I.e. are the signs different? */
- return num1_size;
- num1_sign = num1_size;
- num1_size = ABS (num1_size);
- num2_size = ABS (num2_size);
- tmp1_size = num1_size + den2_size;
- tmp2_size = num2_size + den1_size;
- /* 1. Check to see if we can tell which operand is larger by just looking at
- the number of limbs. */
- /* NUM1 x DEN2 is either TMP1_SIZE limbs or TMP1_SIZE-1 limbs.
- Same for NUM1 x DEN1 with respect to TMP2_SIZE. */
- if (tmp1_size > tmp2_size + 1)
- /* NUM1 x DEN2 is surely larger in magnitude than NUM2 x DEN1. */
- return num1_sign;
- if (tmp2_size > tmp1_size + 1)
- /* NUM1 x DEN2 is surely smaller in magnitude than NUM2 x DEN1. */
- return -num1_sign;
- /* 2. Same, but compare the number of significant bits. */
- {
- int cnt1, cnt2;
- mp_bitcnt_t bits1, bits2;
- count_leading_zeros (cnt1, op1->_mp_num._mp_d[num1_size - 1]);
- count_leading_zeros (cnt2, op2->_mp_den._mp_d[den2_size - 1]);
- bits1 = tmp1_size * GMP_NUMB_BITS - cnt1 - cnt2 + 2 * GMP_NAIL_BITS;
- count_leading_zeros (cnt1, op2->_mp_num._mp_d[num2_size - 1]);
- count_leading_zeros (cnt2, op1->_mp_den._mp_d[den1_size - 1]);
- bits2 = tmp2_size * GMP_NUMB_BITS - cnt1 - cnt2 + 2 * GMP_NAIL_BITS;
- if (bits1 > bits2 + 1)
- return num1_sign;
- if (bits2 > bits1 + 1)
- return -num1_sign;
- }
- /* 3. Finally, cross multiply and compare. */
- TMP_MARK;
- TMP_ALLOC_LIMBS_2 (tmp1_ptr,tmp1_size, tmp2_ptr,tmp2_size);
- if (num1_size >= den2_size)
- tmp1_size -= 0 == mpn_mul (tmp1_ptr,
- op1->_mp_num._mp_d, num1_size,
- op2->_mp_den._mp_d, den2_size);
- else
- tmp1_size -= 0 == mpn_mul (tmp1_ptr,
- op2->_mp_den._mp_d, den2_size,
- op1->_mp_num._mp_d, num1_size);
- if (num2_size >= den1_size)
- tmp2_size -= 0 == mpn_mul (tmp2_ptr,
- op2->_mp_num._mp_d, num2_size,
- op1->_mp_den._mp_d, den1_size);
- else
- tmp2_size -= 0 == mpn_mul (tmp2_ptr,
- op1->_mp_den._mp_d, den1_size,
- op2->_mp_num._mp_d, num2_size);
- cc = tmp1_size - tmp2_size != 0
- ? tmp1_size - tmp2_size : mpn_cmp (tmp1_ptr, tmp2_ptr, tmp1_size);
- TMP_FREE;
- return num1_sign < 0 ? -cc : cc;
- }