compiler/stdc/math/polevll.c

   1 /*      $OpenBSD: polevll.c,v 1.2 2013/11/12 20:35:09 martynas Exp $    */
   2
   3 /*
   4  * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 /*                                                      polevll.c
  20  *                                                      p1evll.c
  21  *
  22  *      Evaluate polynomial
  23  *
  24  *
  25  *
  26  * SYNOPSIS:
  27  *
  28  * int N;
  29  * long double x, y, coef[N+1], polevl[];
  30  *
  31  * y = polevll( x, coef, N );
  32  *
  33  *
  34  *
  35  * DESCRIPTION:
  36  *
  37  * Evaluates polynomial of degree N:
  38  *
  39  *                     2          N
  40  * y  =  C  + C x + C x  +...+ C x
  41  *        0    1     2          N
  42  *
  43  * Coefficients are stored in reverse order:
  44  *
  45  * coef[0] = C  , ..., coef[N] = C  .
  46  *            N                   0
  47  *
  48  *  The function p1evll() assumes that coef[N] = 1.0 and is
  49  * omitted from the array.  Its calling arguments are
  50  * otherwise the same as polevll().
  51  *
  52  *
  53  * SPEED:
  54  *
  55  * In the interest of speed, there are no checks for out
  56  * of bounds arithmetic.  This routine is used by most of
  57  * the functions in the library.  Depending on available
  58  * equipment features, the user may wish to rewrite the
  59  * program in microcode or assembly language.
  60  *
  61  */
  62
  63 #include "math.h"
  64
  65 #include "math_private.h"
  66
  67 /*
  68  * Polynomial evaluator:
  69  *  P[0] x^n  +  P[1] x^(n-1)  +  ...  +  P[n]
  70  */
  71 long double
  72 __polevll(long double x, void *PP, int n)
  73 {
  74         long double y;
  75         long double *P;
  76
  77         P = (long double *)PP;
  78         y = *P++;
  79         do {
  80                 y = y * x + *P++;
  81         } while (--n);
  82
  83         return (y);
  84 }
  85
  86 /*
  87  * Polynomial evaluator:
  88  *  x^n  +  P[0] x^(n-1)  +  P[1] x^(n-2)  +  ...  +  P[n]
  89  */
  90 long double
  91 __p1evll(long double x, void *PP, int n)
  92 {
  93         long double y;
  94         long double *P;
  95
  96         P = (long double *)PP;
  97         n -= 1;
  98         y = x + *P++;
  99         do {
 100                 y = y * x + *P++;
 101         } while (--n);
 102
 103         return (y);
 104 }