Details | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* s_cbrtf.c -- float version of s_cbrt.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
||
| 3 | */ |
||
| 4 | |||
| 5 | /* |
||
| 6 | * ==================================================== |
||
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
||
| 8 | * |
||
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
||
| 10 | * Permission to use, copy, modify, and distribute this |
||
| 11 | * software is freely granted, provided that this notice |
||
| 12 | * is preserved. |
||
| 13 | * ==================================================== |
||
| 14 | */ |
||
| 15 | |||
| 16 | #ifndef lint |
||
| 17 | static char rcsid[] = "$\Id: s_cbrtf.c,v 1.2 1995/05/30 05:49:23 rgrimes Exp $"; |
||
| 18 | #endif |
||
| 19 | |||
| 20 | #include "math.h" |
||
| 21 | #include "math_private.h" |
||
| 22 | |||
| 23 | /* cbrtf(x) |
||
| 24 | * Return cube root of x |
||
| 25 | */ |
||
| 26 | #ifdef __STDC__ |
||
| 27 | static const unsigned |
||
| 28 | #else |
||
| 29 | static unsigned |
||
| 30 | #endif |
||
| 31 | B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */ |
||
| 32 | B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */ |
||
| 33 | |||
| 34 | #ifdef __STDC__ |
||
| 35 | static const float |
||
| 36 | #else |
||
| 37 | static float |
||
| 38 | #endif |
||
| 39 | C = 5.4285717010e-01, /* 19/35 = 0x3f0af8b0 */ |
||
| 40 | D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */ |
||
| 41 | E = 1.4142856598e+00, /* 99/70 = 0x3fb50750 */ |
||
| 42 | F = 1.6071428061e+00, /* 45/28 = 0x3fcdb6db */ |
||
| 43 | G = 3.5714286566e-01; /* 5/14 = 0x3eb6db6e */ |
||
| 44 | |||
| 45 | #ifdef __STDC__ |
||
| 46 | float cbrtf(float x) |
||
| 47 | #else |
||
| 48 | float cbrtf(x) |
||
| 49 | float x; |
||
| 50 | #endif |
||
| 51 | { |
||
| 52 | float r,s,t; |
||
| 53 | int32_t hx; |
||
| 54 | u_int32_t sign; |
||
| 55 | u_int32_t high; |
||
| 56 | |||
| 57 | GET_FLOAT_WORD(hx,x); |
||
| 58 | sign=hx&0x80000000; /* sign= sign(x) */ |
||
| 59 | hx ^=sign; |
||
| 60 | if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */ |
||
| 61 | if(hx==0) |
||
| 62 | return(x); /* cbrt(0) is itself */ |
||
| 63 | |||
| 64 | SET_FLOAT_WORD(x,hx); /* x <- |x| */ |
||
| 65 | /* rough cbrt to 5 bits */ |
||
| 66 | if(hx<0x00800000) /* subnormal number */ |
||
| 67 | {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */ |
||
| 68 | t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2); |
||
| 69 | } |
||
| 70 | else |
||
| 71 | SET_FLOAT_WORD(t,hx/3+B1); |
||
| 72 | |||
| 73 | |||
| 74 | /* new cbrt to 23 bits */ |
||
| 75 | r=t*t/x; |
||
| 76 | s=C+r*t; |
||
| 77 | t*=G+F/(s+E+D/s); |
||
| 78 | |||
| 79 | /* retore the sign bit */ |
||
| 80 | GET_FLOAT_WORD(high,t); |
||
| 81 | SET_FLOAT_WORD(t,high|sign); |
||
| 82 | return(t); |
||
| 83 | } |