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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
/* $OpenBSD: epow.c,v 1.1 2011/07/02 18:11:01 martynas Exp $ */
/*
* Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* epow.c */
/* power function: z = x**y */
/* by Stephen L. Moshier. */
#include "ehead.h"
extern int rndprc;
void epowi();
void epow( x, y, z )
unsigned short *x, *y, *z;
{
unsigned short w[NE];
int rndsav;
long li;
efloor( y, w );
if( ecmp(y,w) == 0 )
{
eifrac( y, &li, w );
if( li < 0 )
li = -li;
if( (li < 0x7fffffff) && (li != 0x80000000) )
{
epowi( x, y, z );
return;
}
}
/* z = exp( y * log(x) ) */
rndsav = rndprc;
rndprc = NBITS;
elog( x, w );
emul( y, w, w );
eexp( w, z );
rndprc = rndsav;
emul( eone, z, z );
}
/* y is integer valued. */
void epowi( x, y, z )
unsigned short x[], y[], z[];
{
unsigned short w[NE];
long li, lx;
unsigned long lu;
int rndsav;
unsigned short signx;
/* unsigned short signy; */
rndsav = rndprc;
eifrac( y, &li, w );
if( li < 0 )
lx = -li;
else
lx = li;
if( (lx == 0x7fffffff) || (lx == 0x80000000) )
{
epow( x, y, z );
goto done;
}
if( (x[NE-1] & (unsigned short )0x7fff) == 0 )
{
if( li == 0 )
{
emov( eone, z );
return;
}
else if( li < 0 )
{
einfin( z );
return;
}
else
{
eclear( z );
return;
}
}
if( li == 0L )
{
emov( eone, z );
return;
}
emov( x, w );
signx = w[NE-1] & (unsigned short )0x8000;
w[NE-1] &= (unsigned short )0x7fff;
/* Overflow detection */
/*
lx = li * (w[NE-1] - 0x3fff);
if( lx > 16385L )
{
einfin( z );
mtherr( "epowi", OVERFLOW );
goto done;
}
if( lx < -16450L )
{
eclear( z );
return;
}
*/
rndprc = NBITS;
if( li < 0 )
{
lu = (unsigned int )( -li );
/* signy = 0xffff;*/
ediv( w, eone, w );
}
else
{
lu = (unsigned int )li;
/* signy = 0;*/
}
/* First bit of the power */
if( lu & 1 )
{
emov( w, z );
}
else
{
emov( eone, z );
signx = 0;
}
lu >>= 1;
while( lu != 0L )
{
emul( w, w, w ); /* arg to the 2-to-the-kth power */
if( lu & 1L ) /* if that bit is set, then include in product */
emul( w, z, z );
lu >>= 1;
}
done:
if( signx )
eneg( z ); /* odd power of negative number */
/*
if( signy )
{
if( ecmp( z, ezero ) != 0 )
{
ediv( z, eone, z );
}
else
{
einfin( z );
printf( "epowi OVERFLOW\n" );
}
}
*/
rndprc = rndsav;
emul( eone, z, z );
}
|
