94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
/* origin: OpenBSD /usr/src/lib/libm/src/polevll.c */
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/*
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* Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Evaluate polynomial
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*
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*
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* SYNOPSIS:
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*
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* int N;
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* long double x, y, coef[N+1], polevl[];
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*
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* y = polevll( x, coef, N );
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*
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*
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* DESCRIPTION:
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*
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* Evaluates polynomial of degree N:
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*
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* 2 N
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* y = C + C x + C x +...+ C x
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* 0 1 2 N
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*
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* Coefficients are stored in reverse order:
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*
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* coef[0] = C , ..., coef[N] = C .
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* N 0
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*
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* The function p1evll() assumes that coef[N] = 1.0 and is
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* omitted from the array. Its calling arguments are
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* otherwise the same as polevll().
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*
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*
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* SPEED:
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*
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* In the interest of speed, there are no checks for out
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* of bounds arithmetic. This routine is used by most of
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* the functions in the library. Depending on available
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* equipment features, the user may wish to rewrite the
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* program in microcode or assembly language.
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*
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*/
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#include "libc/math/libm.h"
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#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
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#else
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/*
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* Polynomial evaluator:
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* P[0] x^n + P[1] x^(n-1) + ... + P[n]
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*/
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long double __polevll(long double x, const long double *P, int n)
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{
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long double y;
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y = *P++;
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do {
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y = y * x + *P++;
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} while (--n);
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return y;
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}
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/*
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* Polynomial evaluator:
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* x^n + P[0] x^(n-1) + P[1] x^(n-2) + ... + P[n]
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*/
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long double __p1evll(long double x, const long double *P, int n)
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{
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long double y;
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n -= 1;
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y = x + *P++;
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do {
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y = y * x + *P++;
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} while (--n);
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return y;
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}
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#endif
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