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
|
/*****************************************************************************/
/*
* testcos.c -- test cosine implementation.
*
* Copyright (C) 1997 Thomas Sailer (sailer@ife.ee.ethz.ch)
* Swiss Federal Institute of Technology (ETH), Electronics Lab
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
/*****************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
/* --------------------------------------------------------------------- */
#define SINTABBITS 9
#define SINTABSIZE (1<<SINTABBITS)
static float sintab[SINTABSIZE+SINTABSIZE/4];
static short isintab[SINTABSIZE+SINTABSIZE/4];
/* --------------------------------------------------------------------- */
static /*__inline__*/ float ftblcos(unsigned int arg)
{
unsigned int x;
int dx;
float s, c;
x = (arg + (0x8000 >> SINTABBITS)) & (0xffffu & (0xffffu << (16-SINTABBITS)));
dx = arg - x;
x >>= (16-SINTABBITS);
c = sintab[x+(0x4000 >> (16-SINTABBITS))];
s = sintab[x];
return c - s * (float)(M_PI/32768.0) * dx;
}
/* --------------------------------------------------------------------- */
static /*__inline__*/ short itblcos(unsigned int arg)
{
unsigned int x;
int dx;
int s, c;
x = (arg + (0x8000 >> SINTABBITS)) & (0xffffu & (0xffffu << (16-SINTABBITS)));
dx = arg - x;
x >>= (16-SINTABBITS);
c = isintab[x+(0x4000 >> (16-SINTABBITS))];
s = isintab[x];
return c - ((s * dx * (int)(M_PI*64.0)) >> 21);
}
/* --------------------------------------------------------------------- */
int main(int argc, char *argv[])
{
float relerr = 0, abserr = 0, irelerr = 0, iabserr = 0, f1, f2, f3, f4;
int i;
for (i = 0; i < (SINTABSIZE+SINTABSIZE/4); i++)
isintab[i] = 32767.0 * (sintab[i] = sin(2.0 * M_PI / SINTABSIZE * i));
for (i = 0; i < 65536; i++) {
f1 = cos(M_PI / 32768.0 * i);
f2 = ftblcos(i);
f3 = fabs(f1-f2);
if (f1 != 0)
f4 = f3 / f1;
else
f4 = 0;
if (f3 > abserr)
abserr = f3;
if (f4 > relerr)
relerr = f4;
f2 = itblcos(i) / 32767.0;
f3 = fabs(f1-f2);
if (f1 != 0)
f4 = f3 / f1;
else
f4 = 0;
if (f3 > iabserr)
iabserr = f3;
if (f4 > irelerr)
irelerr = f4;
}
printf("maximum relative error: %10.5f maximum absolute error: %10.8f\n", relerr, abserr);
printf("integer version: maximum relative error: %10.5f maximum absolute error: %10.8f\n",
irelerr, iabserr);
exit(0);
}
|
