summaryrefslogtreecommitdiff
path: root/src/math/lgammaf_r.c
blob: dc65bace3247a39562f92923840882dba1f8729b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
/* origin: FreeBSD /usr/src/lib/msun/src/e_lgammaf_r.c */
/*
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "libm.h"
#include "libc.h"

static const float
two23= 8.3886080000e+06, /* 0x4b000000 */
pi  =  3.1415927410e+00, /* 0x40490fdb */
a0  =  7.7215664089e-02, /* 0x3d9e233f */
a1  =  3.2246702909e-01, /* 0x3ea51a66 */
a2  =  6.7352302372e-02, /* 0x3d89f001 */
a3  =  2.0580807701e-02, /* 0x3ca89915 */
a4  =  7.3855509982e-03, /* 0x3bf2027e */
a5  =  2.8905137442e-03, /* 0x3b3d6ec6 */
a6  =  1.1927076848e-03, /* 0x3a9c54a1 */
a7  =  5.1006977446e-04, /* 0x3a05b634 */
a8  =  2.2086278477e-04, /* 0x39679767 */
a9  =  1.0801156895e-04, /* 0x38e28445 */
a10 =  2.5214456400e-05, /* 0x37d383a2 */
a11 =  4.4864096708e-05, /* 0x383c2c75 */
tc  =  1.4616321325e+00, /* 0x3fbb16c3 */
tf  = -1.2148628384e-01, /* 0xbdf8cdcd */
/* tt = -(tail of tf) */
tt  =  6.6971006518e-09, /* 0x31e61c52 */
t0  =  4.8383611441e-01, /* 0x3ef7b95e */
t1  = -1.4758771658e-01, /* 0xbe17213c */
t2  =  6.4624942839e-02, /* 0x3d845a15 */
t3  = -3.2788541168e-02, /* 0xbd064d47 */
t4  =  1.7970675603e-02, /* 0x3c93373d */
t5  = -1.0314224288e-02, /* 0xbc28fcfe */
t6  =  6.1005386524e-03, /* 0x3bc7e707 */
t7  = -3.6845202558e-03, /* 0xbb7177fe */
t8  =  2.2596477065e-03, /* 0x3b141699 */
t9  = -1.4034647029e-03, /* 0xbab7f476 */
t10 =  8.8108185446e-04, /* 0x3a66f867 */
t11 = -5.3859531181e-04, /* 0xba0d3085 */
t12 =  3.1563205994e-04, /* 0x39a57b6b */
t13 = -3.1275415677e-04, /* 0xb9a3f927 */
t14 =  3.3552918467e-04, /* 0x39afe9f7 */
u0  = -7.7215664089e-02, /* 0xbd9e233f */
u1  =  6.3282704353e-01, /* 0x3f2200f4 */
u2  =  1.4549225569e+00, /* 0x3fba3ae7 */
u3  =  9.7771751881e-01, /* 0x3f7a4bb2 */
u4  =  2.2896373272e-01, /* 0x3e6a7578 */
u5  =  1.3381091878e-02, /* 0x3c5b3c5e */
v1  =  2.4559779167e+00, /* 0x401d2ebe */
v2  =  2.1284897327e+00, /* 0x4008392d */
v3  =  7.6928514242e-01, /* 0x3f44efdf */
v4  =  1.0422264785e-01, /* 0x3dd572af */
v5  =  3.2170924824e-03, /* 0x3b52d5db */
s0  = -7.7215664089e-02, /* 0xbd9e233f */
s1  =  2.1498242021e-01, /* 0x3e5c245a */
s2  =  3.2577878237e-01, /* 0x3ea6cc7a */
s3  =  1.4635047317e-01, /* 0x3e15dce6 */
s4  =  2.6642270386e-02, /* 0x3cda40e4 */
s5  =  1.8402845599e-03, /* 0x3af135b4 */
s6  =  3.1947532989e-05, /* 0x3805ff67 */
r1  =  1.3920053244e+00, /* 0x3fb22d3b */
r2  =  7.2193557024e-01, /* 0x3f38d0c5 */
r3  =  1.7193385959e-01, /* 0x3e300f6e */
r4  =  1.8645919859e-02, /* 0x3c98bf54 */
r5  =  7.7794247773e-04, /* 0x3a4beed6 */
r6  =  7.3266842264e-06, /* 0x36f5d7bd */
w0  =  4.1893854737e-01, /* 0x3ed67f1d */
w1  =  8.3333335817e-02, /* 0x3daaaaab */
w2  = -2.7777778450e-03, /* 0xbb360b61 */
w3  =  7.9365057172e-04, /* 0x3a500cfd */
w4  = -5.9518753551e-04, /* 0xba1c065c */
w5  =  8.3633989561e-04, /* 0x3a5b3dd2 */
w6  = -1.6309292987e-03; /* 0xbad5c4e8 */

static float sin_pif(float x)
{
	float y,z;
	int n,ix;

	GET_FLOAT_WORD(ix, x);
	ix &= 0x7fffffff;

	if(ix < 0x3e800000)
		return __sindf(pi*x);

	y = -x;  /* negative x is assumed */

	/*
	 * argument reduction, make sure inexact flag not raised if input
	 * is an integer
	 */
	z = floorf(y);
	if (z != y) {   /* inexact anyway */
		y *= 0.5f;
		y  = 2.0f*(y - floorf(y));   /* y = |x| mod 2.0 */
		n  = (int)(y*4.0f);
	} else {
		if (ix >= 0x4b800000) {
			y = 0.0f;  /* y must be even */
			n = 0;
		} else {
			if (ix < 0x4b000000)
				z = y + two23;  /* exact */
			GET_FLOAT_WORD(n, z);
			n &= 1;
			y = n;
			n <<= 2;
		}
	}
	switch (n) {
	case 0:  y =  __sindf(pi*y); break;
	case 1:
	case 2:  y =  __cosdf(pi*(0.5f - y)); break;
	case 3:
	case 4:  y =  __sindf(pi*(1.0f - y)); break;
	case 5:
	case 6:  y = -__cosdf(pi*(y - 1.5f)); break;
	default: y =  __sindf(pi*(y - 2.0f)); break;
	}
	return -y;
}


float __lgammaf_r(float x, int *signgamp)
{
	float t,y,z,nadj,p,p1,p2,p3,q,r,w;
	int32_t hx;
	int i,ix;

	GET_FLOAT_WORD(hx, x);

	/* purge off +-inf, NaN, +-0, tiny and negative arguments */
	*signgamp = 1;
	ix = hx & 0x7fffffff;
	if (ix >= 0x7f800000)
		return x*x;
	if (ix == 0)
		return 1.0f/0.0f;
	if (ix < 0x35000000) {  /* |x| < 2**-21, return -log(|x|) */
		if (hx < 0) {
			*signgamp = -1;
			return -logf(-x);
		}
		return -logf(x);
	}
	if (hx < 0) {
		if (ix >= 0x4b000000)  /* |x| >= 2**23, must be -integer */
			return 1.0f/0.0f;
		t = sin_pif(x);
		if (t == 0.0f) /* -integer */
			return 1.0f/0.0f;
		nadj = logf(pi/fabsf(t*x));
		if (t < 0.0f)
			*signgamp = -1;
		x = -x;
	}

	/* purge off 1 and 2 */
	if (ix == 0x3f800000 || ix == 0x40000000)
		r = 0;
	/* for x < 2.0 */
	else if (ix < 0x40000000) {
		if (ix <= 0x3f666666) {  /* lgamma(x) = lgamma(x+1)-log(x) */
			r = -logf(x);
			if (ix >= 0x3f3b4a20) {
				y = 1.0f - x;
				i = 0;
			} else if (ix >= 0x3e6d3308) {
				y = x - (tc-1.0f);
				i = 1;
			} else {
				y = x;
				i = 2;
			}
		} else {
			r = 0.0f;
			if (ix >= 0x3fdda618) {  /* [1.7316,2] */
				y = 2.0f - x;
				i = 0;
			} else if (ix >= 0x3F9da620) {  /* [1.23,1.73] */
				y = x - tc;
				i = 1;
			} else {
				y = x - 1.0f;
				i = 2;
			}
		}
		switch(i) {
		case 0:
			z = y*y;
			p1 = a0+z*(a2+z*(a4+z*(a6+z*(a8+z*a10))));
			p2 = z*(a1+z*(a3+z*(a5+z*(a7+z*(a9+z*a11)))));
			p = y*p1+p2;
			r += p - 0.5f*y;
			break;
		case 1:
			z = y*y;
			w = z*y;
			p1 = t0+w*(t3+w*(t6+w*(t9 +w*t12)));    /* parallel comp */
			p2 = t1+w*(t4+w*(t7+w*(t10+w*t13)));
			p3 = t2+w*(t5+w*(t8+w*(t11+w*t14)));
			p = z*p1-(tt-w*(p2+y*p3));
			r += (tf + p);
			break;
		case 2:
			p1 = y*(u0+y*(u1+y*(u2+y*(u3+y*(u4+y*u5)))));
			p2 = 1.0f+y*(v1+y*(v2+y*(v3+y*(v4+y*v5))));
			r += -0.5f*y + p1/p2;
		}
	} else if (ix < 0x41000000) {  /* x < 8.0 */
		i = (int)x;
		y = x - (float)i;
		p = y*(s0+y*(s1+y*(s2+y*(s3+y*(s4+y*(s5+y*s6))))));
		q = 1.0f+y*(r1+y*(r2+y*(r3+y*(r4+y*(r5+y*r6)))));
		r = 0.5f*y+p/q;
		z = 1.0f;    /* lgamma(1+s) = log(s) + lgamma(s) */
		switch (i) {
		case 7: z *= y + 6.0f;  /* FALLTHRU */
		case 6: z *= y + 5.0f;  /* FALLTHRU */
		case 5: z *= y + 4.0f;  /* FALLTHRU */
		case 4: z *= y + 3.0f;  /* FALLTHRU */
		case 3: z *= y + 2.0f;  /* FALLTHRU */
			r += logf(z);
			break;
		}
	} else if (ix < 0x5c800000) {  /* 8.0 <= x < 2**58 */
		t = logf(x);
		z = 1.0f/x;
		y = z*z;
		w = w0+z*(w1+y*(w2+y*(w3+y*(w4+y*(w5+y*w6)))));
		r = (x-0.5f)*(t-1.0f)+w;
	} else                         /* 2**58 <= x <= inf */
		r =  x*(logf(x)-1.0f);
	if (hx < 0)
		r = nadj - r;
	return r;
}

weak_alias(__lgammaf_r, lgammaf_r);