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cmp_d.c revision 1.1.1.1 
      1 /* mpz_cmp_d -- compare absolute values of mpz and double.
      2 
      3 Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
      4 
      5 This file is part of the GNU MP Library.
      6 
      7 The GNU MP Library is free software; you can redistribute it and/or modify
      8 it under the terms of the GNU Lesser General Public License as published by
      9 the Free Software Foundation; either version 3 of the License, or (at your
     10 option) any later version.
     11 
     12 The GNU MP Library is distributed in the hope that it will be useful, but
     13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     14 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     15 License for more details.
     16 
     17 You should have received a copy of the GNU Lesser General Public License
     18 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
     19 
     20 #include "config.h"
     21 
     22 #if HAVE_FLOAT_H
     23 #include <float.h>  /* for DBL_MAX */
     24 #endif
     25 
     26 #include "gmp.h"
     27 #include "gmp-impl.h"
     28 
     29 
     30 #define RETURN_CMP(zl, dl)                      \
     31   do {                                          \
     32     zlimb = (zl);                               \
     33     dlimb = (dl);                               \
     34     if (zlimb != dlimb)                         \
     35       return (zlimb >= dlimb ? ret : -ret);     \
     36   } while (0)
     37 
     38 #define RETURN_NONZERO(ptr, size, val)          \
     39   do {                                          \
     40     mp_size_t __i;                              \
     41     for (__i = (size)-1; __i >= 0; __i--)       \
     42       if ((ptr)[__i] != 0)                      \
     43         return val;                             \
     44     return 0;                                   \
     45   } while (0)
     46 
     47 
     48 int
     49 mpz_cmp_d (mpz_srcptr z, double d)
     50 {
     51   mp_limb_t  darray[LIMBS_PER_DOUBLE], zlimb, dlimb;
     52   mp_srcptr  zp;
     53   mp_size_t  zsize;
     54   int        dexp, ret;
     55 
     56   /* d=NaN is an invalid operation, there's no sensible return value.
     57      d=Inf or -Inf is always bigger than z.  */
     58   DOUBLE_NAN_INF_ACTION (d, __gmp_invalid_operation (), goto z_zero);
     59 
     60   /* 1. Either operand zero. */
     61   zsize = SIZ(z);
     62   if (d == 0.0)
     63     return zsize;
     64   if (zsize == 0)
     65     {
     66     z_zero:
     67       return (d < 0.0 ? 1 : -1);
     68     }
     69 
     70   /* 2. Opposite signs. */
     71   if (zsize >= 0)
     72     {
     73       if (d < 0.0)
     74         return 1;    /* >=0 cmp <0 */
     75       ret = 1;
     76     }
     77   else
     78     {
     79       if (d >= 0.0)
     80         return -1;   /* <0 cmp >=0 */
     81       ret = -1;
     82       d = -d;
     83       zsize = -zsize;
     84     }
     85 
     86   /* 3. Small d, knowing abs(z) >= 1. */
     87   if (d < 1.0)
     88     return ret;
     89 
     90   dexp = __gmp_extract_double (darray, d);
     91   ASSERT (dexp >= 1);
     92 
     93   /* 4. Check for different high limb positions. */
     94   if (zsize != dexp)
     95     return (zsize >= dexp ? ret : -ret);
     96 
     97   /* 5. Limb data. */
     98   zp = PTR(z);
     99 
    100 #if LIMBS_PER_DOUBLE == 2
    101   RETURN_CMP (zp[zsize-1], darray[1]);
    102   if (zsize == 1)
    103     return (darray[0] != 0 ? -ret : 0);
    104 
    105   RETURN_CMP (zp[zsize-2], darray[0]);
    106   RETURN_NONZERO (zp, zsize-2, ret);
    107 #endif
    108 
    109 #if LIMBS_PER_DOUBLE == 3
    110   RETURN_CMP (zp[zsize-1], darray[2]);
    111   if (zsize == 1)
    112     return ((darray[0] | darray[1]) != 0 ? -ret : 0);
    113 
    114   RETURN_CMP (zp[zsize-2], darray[1]);
    115   if (zsize == 2)
    116     return (darray[0] != 0 ? -ret : 0);
    117 
    118   RETURN_CMP (zp[zsize-3], darray[0]);
    119   RETURN_NONZERO (zp, zsize-3, ret);
    120 #endif
    121 
    122 #if LIMBS_PER_DOUBLE >= 4
    123   {
    124     int i;
    125     for (i = 1; i <= LIMBS_PER_DOUBLE; i++)
    126       {
    127 	RETURN_CMP (zp[zsize-i], darray[LIMBS_PER_DOUBLE-i]);
    128 	if (i >= zsize)
    129 	  RETURN_NONZERO (darray, LIMBS_PER_DOUBLE-i, -ret);
    130       }
    131     RETURN_NONZERO (zp, zsize-LIMBS_PER_DOUBLE, ret);
    132   }
    133 #endif
    134 }
    135