1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
/* mpfr_eq -- Compare two floats up to a specified bit #.
Copyright 1999, 2001, 2003-2004, 2006-2021 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU MPFR 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 MPFR 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 MPFR Library; see the file COPYING.LESSER. If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include "mpfr-impl.h"
/* return non-zero if the first n_bits bits of u, v are equal,
0 otherwise */
int
mpfr_eq (mpfr_srcptr u, mpfr_srcptr v, unsigned long int n_bits)
{
mpfr_limb_srcptr up, vp;
mp_size_t usize, vsize, size, i;
mpfr_exp_t uexp, vexp;
int k;
if (MPFR_ARE_SINGULAR(u, v))
{
if (MPFR_IS_NAN(u) || MPFR_IS_NAN(v))
return 0; /* non equal */
else if (MPFR_IS_INF(u) && MPFR_IS_INF(v))
return (MPFR_SIGN(u) == MPFR_SIGN(v));
else if (MPFR_IS_ZERO(u) && MPFR_IS_ZERO(v))
return 1;
else
return 0;
}
/* 1. Are the signs different? */
if (MPFR_SIGN(u) != MPFR_SIGN(v))
return 0;
uexp = MPFR_GET_EXP (u);
vexp = MPFR_GET_EXP (v);
/* 2. Are the exponents different? */
if (uexp != vexp)
return 0; /* no bit agree */
usize = MPFR_LIMB_SIZE (u);
vsize = MPFR_LIMB_SIZE (v);
if (vsize > usize) /* exchange u and v */
{
up = MPFR_MANT(v);
vp = MPFR_MANT(u);
size = vsize;
vsize = usize;
usize = size;
}
else
{
up = MPFR_MANT(u);
vp = MPFR_MANT(v);
}
/* now usize >= vsize */
MPFR_ASSERTD(usize >= vsize);
if (usize > vsize)
{
if ((unsigned long) vsize * GMP_NUMB_BITS < n_bits)
{
/* check if low min(PREC(u), n_bits) - (vsize * GMP_NUMB_BITS)
bits from u are non-zero */
unsigned long remains = n_bits - (vsize * GMP_NUMB_BITS);
k = usize - vsize - 1;
while (k >= 0 && remains >= GMP_NUMB_BITS && !up[k])
{
k--;
remains -= GMP_NUMB_BITS;
}
/* now either k < 0: all low bits from u are zero
or remains < GMP_NUMB_BITS: check high bits from up[k]
or up[k] <> 0: different */
if (k >= 0 && (((remains < GMP_NUMB_BITS) &&
(up[k] >> (GMP_NUMB_BITS - remains))) ||
(remains >= GMP_NUMB_BITS && up[k])))
return 0; /* surely too different */
}
size = vsize;
}
else
{
size = usize;
}
/* now size = min (usize, vsize) */
/* If size is too large wrt n_bits, reduce it to look only at the
high n_bits bits.
Otherwise, if n_bits > size * GMP_NUMB_BITS, reduce n_bits to
size * GMP_NUMB_BITS, since the extra low bits of one of the
operands have already been check above. */
if ((unsigned long) size > 1 + (n_bits - 1) / GMP_NUMB_BITS)
size = 1 + (n_bits - 1) / GMP_NUMB_BITS;
else if (n_bits > (unsigned long) size * GMP_NUMB_BITS)
n_bits = size * GMP_NUMB_BITS;
up += usize - size;
vp += vsize - size;
for (i = size - 1; i > 0 && n_bits >= GMP_NUMB_BITS; i--)
{
if (up[i] != vp[i])
return 0;
n_bits -= GMP_NUMB_BITS;
}
/* now either i=0 or n_bits<GMP_NUMB_BITS */
/* since n_bits <= size * GMP_NUMB_BITS before the above for-loop,
we have the invariant n_bits <= (i+1) * GMP_NUMB_BITS, thus
we always have n_bits <= GMP_NUMB_BITS here */
MPFR_ASSERTD(n_bits <= GMP_NUMB_BITS);
if (n_bits & (GMP_NUMB_BITS - 1))
return (up[i] >> (GMP_NUMB_BITS - (n_bits & (GMP_NUMB_BITS - 1))) ==
vp[i] >> (GMP_NUMB_BITS - (n_bits & (GMP_NUMB_BITS - 1))));
else
return (up[i] == vp[i]);
}
|
