1 /* origin: OpenBSD /usr/src/lib/libm/src/polevll.c */
2 /*
3 * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17 /*
18 * Evaluate polynomial
19 *
20 *
21 * SYNOPSIS:
22 *
23 * int N;
24 * long double x, y, coef[N+1], polevl[];
25 *
26 * y = polevll( x, coef, N );
27 *
28 *
29 * DESCRIPTION:
30 *
31 * Evaluates polynomial of degree N:
32 *
33 * 2 N
34 * y = C + C x + C x +...+ C x
35 * 0 1 2 N
36 *
37 * Coefficients are stored in reverse order:
38 *
39 * coef[0] = C , ..., coef[N] = C .
40 * N 0
41 *
42 * The function p1evll() assumes that coef[N] = 1.0 and is
43 * omitted from the array. Its calling arguments are
44 * otherwise the same as polevll().
45 *
46 *
47 * SPEED:
48 *
49 * In the interest of speed, there are no checks for out
50 * of bounds arithmetic. This routine is used by most of
51 * the functions in the library. Depending on available
52 * equipment features, the user may wish to rewrite the
53 * program in microcode or assembly language.
54 *
55 */
56 57 #include "libm.h"
58 59 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
60 #else
61 /*
62 * Polynomial evaluator:
63 * P[0] x^n + P[1] x^(n-1) + ... + P[n]
64 */
65 long double __polevll(long double x, const long double *P, int n)
66 {
67 long double y;
68 69 y = *P++;
70 do {
71 y = y * x + *P++;
72 } while (--n);
73 74 return y;
75 }
76 77 /*
78 * Polynomial evaluator:
79 * x^n + P[0] x^(n-1) + P[1] x^(n-2) + ... + P[n]
80 */
81 long double __p1evll(long double x, const long double *P, int n)
82 {
83 long double y;
84 85 n -= 1;
86 y = x + *P++;
87 do {
88 y = y * x + *P++;
89 } while (--n);
90 91 return y;
92 }
93 #endif
94