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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* s_log1pf.c -- float version of s_log1p.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |||
| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | */ |
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| 15 | |||
| 16 | #ifndef lint |
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| 17 | static char rcsid[] = "$\Id: s_log1pf.c,v 1.2 1995/05/30 05:49:58 rgrimes Exp $"; |
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| 18 | #endif |
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| 19 | |||
| 20 | #include "math.h" |
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| 21 | #include "math_private.h" |
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| 22 | |||
| 23 | #ifdef __STDC__ |
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| 24 | static const float |
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| 25 | #else |
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| 26 | static float |
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| 27 | #endif |
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| 28 | ln2_hi = 6.9313812256e-01, /* 0x3f317180 */ |
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| 29 | ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */ |
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| 30 | two25 = 3.355443200e+07, /* 0x4c000000 */ |
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| 31 | Lp1 = 6.6666668653e-01, /* 3F2AAAAB */ |
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| 32 | Lp2 = 4.0000000596e-01, /* 3ECCCCCD */ |
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| 33 | Lp3 = 2.8571429849e-01, /* 3E924925 */ |
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| 34 | Lp4 = 2.2222198546e-01, /* 3E638E29 */ |
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| 35 | Lp5 = 1.8183572590e-01, /* 3E3A3325 */ |
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| 36 | Lp6 = 1.5313838422e-01, /* 3E1CD04F */ |
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| 37 | Lp7 = 1.4798198640e-01; /* 3E178897 */ |
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| 38 | |||
| 39 | #ifdef __STDC__ |
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| 40 | static const float zero = 0.0; |
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| 41 | #else |
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| 42 | static float zero = 0.0; |
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| 43 | #endif |
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| 44 | |||
| 45 | #ifdef __STDC__ |
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| 46 | float log1pf(float x) |
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| 47 | #else |
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| 48 | float log1pf(x) |
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| 49 | float x; |
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| 50 | #endif |
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| 51 | { |
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| 52 | float hfsq,f,c,s,z,R,u; |
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| 53 | int32_t k,hx,hu,ax; |
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| 54 | |||
| 55 | GET_FLOAT_WORD(hx,x); |
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| 56 | ax = hx&0x7fffffff; |
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| 57 | |||
| 58 | k = 1; |
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| 59 | if (hx < 0x3ed413d7) { /* x < 0.41422 */ |
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| 60 | if(ax>=0x3f800000) { /* x <= -1.0 */ |
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| 61 | if(x==(float)-1.0) return -two25/zero; /* log1p(-1)=+inf */ |
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| 62 | else return (x-x)/(x-x); /* log1p(x<-1)=NaN */ |
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| 63 | } |
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| 64 | if(ax<0x31000000) { /* |x| < 2**-29 */ |
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| 65 | if(two25+x>zero /* raise inexact */ |
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| 66 | &&ax<0x24800000) /* |x| < 2**-54 */ |
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| 67 | return x; |
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| 68 | else |
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| 69 | return x - x*x*(float)0.5; |
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| 70 | } |
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| 71 | if(hx>0||hx<=((int32_t)0xbe95f61f)) { |
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| 72 | k=0;f=x;hu=1;} /* -0.2929<x<0.41422 */ |
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| 73 | } |
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| 74 | if (hx >= 0x7f800000) return x+x; |
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| 75 | if(k!=0) { |
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| 76 | if(hx<0x5a000000) { |
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| 77 | u = (float)1.0+x; |
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| 78 | GET_FLOAT_WORD(hu,u); |
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| 79 | k = (hu>>23)-127; |
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| 80 | /* correction term */ |
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| 81 | c = (k>0)? (float)1.0-(u-x):x-(u-(float)1.0); |
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| 82 | c /= u; |
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| 83 | } else { |
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| 84 | u = x; |
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| 85 | GET_FLOAT_WORD(hu,u); |
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| 86 | k = (hu>>23)-127; |
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| 87 | c = 0; |
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| 88 | } |
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| 89 | hu &= 0x007fffff; |
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| 90 | if(hu<0x3504f7) { |
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| 91 | SET_FLOAT_WORD(u,hu|0x3f800000);/* normalize u */ |
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| 92 | } else { |
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| 93 | k += 1; |
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| 94 | SET_FLOAT_WORD(u,hu|0x3f000000); /* normalize u/2 */ |
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| 95 | hu = (0x00800000-hu)>>2; |
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| 96 | } |
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| 97 | f = u-(float)1.0; |
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| 98 | } |
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| 99 | hfsq=(float)0.5*f*f; |
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| 100 | if(hu==0) { /* |f| < 2**-20 */ |
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| 101 | if(f==zero) if(k==0) return zero; |
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| 102 | else {c += k*ln2_lo; return k*ln2_hi+c;} |
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| 103 | R = hfsq*((float)1.0-(float)0.66666666666666666*f); |
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| 104 | if(k==0) return f-R; else |
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| 105 | return k*ln2_hi-((R-(k*ln2_lo+c))-f); |
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| 106 | } |
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| 107 | s = f/((float)2.0+f); |
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| 108 | z = s*s; |
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| 109 | R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7)))))); |
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| 110 | if(k==0) return f-(hfsq-s*(hfsq+R)); else |
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| 111 | return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f); |
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| 112 | } |