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comparison packages/language/c/libm/current/src/float/portable-api/sf_cbrt.c @ 3260:77f9d3253c3e

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Add: Complex number header and library (single and double precision floating point), port from Newlib. Add: Single precision floating point library, port from Newlib. [ Bugzilla 1001539 ]
author vae
date Sun, 25 Aug 2013 14:38:57 +0000
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3259:8ecac279f33c 3260:77f9d3253c3e
1 //===========================================================================
2 //
3 // sf_cbrt.c
4 //
5 // Part of the standard mathematical function library
6 //
7 //===========================================================================
8 // ####ECOSGPLCOPYRIGHTBEGIN####
9 // -------------------------------------------
10 // This file is part of eCos, the Embedded Configurable Operating System.
11 // Copyright (C) 2012 Free Software Foundation, Inc.
12 //
13 // eCos is free software; you can redistribute it and/or modify it under
14 // the terms of the GNU General Public License as published by the Free
15 // Software Foundation; either version 2 or (at your option) any later
16 // version.
17 //
18 // eCos is distributed in the hope that it will be useful, but WITHOUT
19 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
20 // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
21 // for more details.
22 //
23 // You should have received a copy of the GNU General Public License
24 // along with eCos; if not, write to the Free Software Foundation, Inc.,
25 // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
26 //
27 // As a special exception, if other files instantiate templates or use
28 // macros or inline functions from this file, or you compile this file
29 // and link it with other works to produce a work based on this file,
30 // this file does not by itself cause the resulting work to be covered by
31 // the GNU General Public License. However the source code for this file
32 // must still be made available in accordance with section (3) of the GNU
33 // General Public License v2.
34 //
35 // This exception does not invalidate any other reasons why a work based
36 // on this file might be covered by the GNU General Public License.
37 // -------------------------------------------
38 // ####ECOSGPLCOPYRIGHTEND####
39 //===========================================================================
40 //#####DESCRIPTIONBEGIN####
41 //
42 // Author(s):
43 // Contributors: visar, ilijak
44 // Date: 2012-03-08
45 // Purpose:
46 // Description:
47 // Usage:
48 //
49 //####DESCRIPTIONEND####
50 //
51 //===========================================================================
52
53 // CONFIGURATION
54
55 #include <pkgconf/libm.h> // Configuration header
56
57 // Include the Math library?
58 #ifdef CYGPKG_LIBM
59
60 // Derived from code with the following copyright
61
62
63 /* sf_cbrt.c -- float version of s_cbrt.c.
64 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
65 */
66
67 /*
68 * ====================================================
69 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
70 *
71 * Developed at SunPro, a Sun Microsystems, Inc. business.
72 * Permission to use, copy, modify, and distribute this
73 * software is freely granted, provided that this notice
74 * is preserved.
75 * ====================================================
76 *
77 */
78
79
80 #include "mathincl/fdlibm.h"
81
82 /* cbrtf(x)
83 * Return cube root of x
84 */
85 #ifdef __STDC__
86 static const __uint32_t
87 #else
88 static __uint32_t
89 #endif
90 B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
91 B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
92
93 #ifdef __STDC__
94 static const float
95 #else
96 static float
97 #endif
98 C = 5.4285717010e-01, /* 19/35 = 0x3f0af8b0 */
99 D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
100 E = 1.4142856598e+00, /* 99/70 = 0x3fb50750 */
101 F = 1.6071428061e+00, /* 45/28 = 0x3fcdb6db */
102 G = 3.5714286566e-01; /* 5/14 = 0x3eb6db6e */
103
104 #ifdef __STDC__
105 float cbrtf(float x)
106 #else
107 float cbrtf(x)
108 float x;
109 #endif
110 {
111 __int32_t hx;
112 float r,s,t;
113 __uint32_t sign;
114 __uint32_t high;
115
116 hx = CYG_LIBM_WORD(x);
117 sign=hx&0x80000000; /* sign= sign(x) */
118 hx ^=sign;
119 if(!FLT_UWORD_IS_FINITE(hx))
120 return(x+x); /* cbrt(NaN,INF) is itself */
121 if(FLT_UWORD_IS_ZERO(hx))
122 return(x); /* cbrt(0) is itself */
123
124 SET_FLOAT_WORD(x,hx); /* x <- |x| */
125 /* rough cbrt to 5 bits */
126 if(FLT_UWORD_IS_SUBNORMAL(hx)) /* subnormal number */
127 {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
128 t*=x; high = CYG_LIBM_WORD(t); SET_FLOAT_WORD(t,high/3+B2);
129 }
130 else
131 SET_FLOAT_WORD(t,hx/3+B1);
132
133
134 /* new cbrt to 23 bits */
135 r=t*t/x;
136 s=C+r*t;
137 t*=G+F/(s+E+D/s);
138
139 /* retore the sign bit */
140 high = CYG_LIBM_WORD(t);
141 SET_FLOAT_WORD(t,high|sign);
142 return(t);
143 }
144
145 #endif // ifdef CYGPKG_LIBM
146
147 // EOF sf_cbrt.c