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Annotation of OpenXM_contrib/gmp/mpq/cmp.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpq_cmp(u,v) -- Compare U, V.  Return postive, zero, or negative
                      2:    based on if U > V, U == V, or U < V.
                      3:
                      4: Copyright (C) 1991, 1994, 1996 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 the GNU Library General Public License as published by
                     10: the Free Software Foundation; either version 2 of the License, or (at your
                     11: option) any later version.
                     12:
                     13: The GNU MP 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 Library General Public
                     16: License for more details.
                     17:
                     18: You should have received a copy of the GNU Library General Public License
                     19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA. */
                     22:
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25: #include "longlong.h"
                     26:
                     27: int
                     28: #if __STDC__
                     29: mpq_cmp (const MP_RAT *op1, const MP_RAT *op2)
                     30: #else
                     31: mpq_cmp (op1, op2)
                     32:      const MP_RAT *op1;
                     33:      const MP_RAT *op2;
                     34: #endif
                     35: {
                     36:   mp_size_t num1_size = op1->_mp_num._mp_size;
                     37:   mp_size_t den1_size = op1->_mp_den._mp_size;
                     38:   mp_size_t num2_size = op2->_mp_num._mp_size;
                     39:   mp_size_t den2_size = op2->_mp_den._mp_size;
                     40:   mp_size_t tmp1_size, tmp2_size;
                     41:   mp_ptr tmp1_ptr, tmp2_ptr;
                     42:   mp_size_t num1_sign;
                     43:   int cc;
                     44:   TMP_DECL (marker);
                     45:
                     46:   if (num1_size == 0)
                     47:     return -num2_size;
                     48:   if (num2_size == 0)
                     49:     return num1_size;
                     50:   if ((num1_size ^ num2_size) < 0) /* I.e. are the signs different? */
                     51:     return num1_size;
                     52:
                     53:   num1_sign = num1_size;
                     54:   num1_size = ABS (num1_size);
                     55:   num2_size = ABS (num2_size);
                     56:
                     57:   tmp1_size = num1_size + den2_size;
                     58:   tmp2_size = num2_size + den1_size;
                     59:
                     60:   /* 1. Check to see if we can tell which operand is larger by just looking at
                     61:      the number of limbs.  */
                     62:
                     63:   /* NUM1 x DEN2 is either TMP1_SIZE limbs or TMP1_SIZE-1 limbs.
                     64:      Same for NUM1 x DEN1 with respect to TMP2_SIZE.  */
                     65:   if (tmp1_size > tmp2_size + 1)
                     66:     /* NUM1 x DEN2 is surely larger in magnitude than NUM2 x DEN1.  */
                     67:     return num1_sign;
                     68:   if (tmp2_size > tmp1_size + 1)
                     69:     /* NUM1 x DEN2 is surely smaller in magnitude than NUM2 x DEN1.  */
                     70:     return -num1_sign;
                     71:
                     72:   /* 2. Same, but compare the number of significant bits.  */
                     73:   {
                     74:     int cnt1, cnt2;
                     75:     unsigned long int bits1, bits2;
                     76:
                     77:     count_leading_zeros (cnt1, op1->_mp_num._mp_d[num1_size - 1]);
                     78:     count_leading_zeros (cnt2, op2->_mp_den._mp_d[den2_size - 1]);
                     79:     bits1 = tmp1_size * BITS_PER_MP_LIMB - cnt1 - cnt2;
                     80:
                     81:     count_leading_zeros (cnt1, op2->_mp_num._mp_d[num2_size - 1]);
                     82:     count_leading_zeros (cnt2, op1->_mp_den._mp_d[den1_size - 1]);
                     83:     bits2 = tmp2_size * BITS_PER_MP_LIMB - cnt1 - cnt2;
                     84:
                     85:     if (bits1 > bits2 + 1)
                     86:       return num1_sign;
                     87:     if (bits2 > bits1 + 1)
                     88:       return -num1_sign;
                     89:   }
                     90:
                     91:   /* 3. Finally, cross multiply and compare.  */
                     92:
                     93:   TMP_MARK (marker);
                     94:   tmp1_ptr = (mp_ptr) TMP_ALLOC (tmp1_size * BYTES_PER_MP_LIMB);
                     95:   tmp2_ptr = (mp_ptr) TMP_ALLOC (tmp2_size * BYTES_PER_MP_LIMB);
                     96:
                     97:   if (num1_size >= den2_size)
                     98:     tmp1_size -= 0 == mpn_mul (tmp1_ptr,
                     99:                               op1->_mp_num._mp_d, num1_size,
                    100:                               op2->_mp_den._mp_d, den2_size);
                    101:   else
                    102:     tmp1_size -= 0 == mpn_mul (tmp1_ptr,
                    103:                               op2->_mp_den._mp_d, den2_size,
                    104:                               op1->_mp_num._mp_d, num1_size);
                    105:
                    106:    if (num2_size >= den1_size)
                    107:      tmp2_size -= 0 == mpn_mul (tmp2_ptr,
                    108:                                op2->_mp_num._mp_d, num2_size,
                    109:                                op1->_mp_den._mp_d, den1_size);
                    110:    else
                    111:      tmp2_size -= 0 == mpn_mul (tmp2_ptr,
                    112:                                op1->_mp_den._mp_d, den1_size,
                    113:                                op2->_mp_num._mp_d, num2_size);
                    114:
                    115:
                    116:   cc = tmp1_size - tmp2_size != 0
                    117:     ? tmp1_size - tmp2_size : mpn_cmp (tmp1_ptr, tmp2_ptr, tmp1_size);
                    118:   TMP_FREE (marker);
                    119:   return num1_sign < 0 ? -cc : cc;
                    120: }