xref: /freebsd/lib/msun/src/e_j1f.c (revision c98323078dede7579020518ec84cdcb478e5c142)
1 /* e_j1f.c -- float version of e_j1.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[] = "$FreeBSD$";
18 #endif
19 
20 #include "math.h"
21 #include "math_private.h"
22 
23 static float ponef(float), qonef(float);
24 
25 static const float
26 huge    = 1e30,
27 one	= 1.0,
28 invsqrtpi=  5.6418961287e-01, /* 0x3f106ebb */
29 tpi      =  6.3661974669e-01, /* 0x3f22f983 */
30 	/* R0/S0 on [0,2] */
31 r00  = -6.2500000000e-02, /* 0xbd800000 */
32 r01  =  1.4070566976e-03, /* 0x3ab86cfd */
33 r02  = -1.5995563444e-05, /* 0xb7862e36 */
34 r03  =  4.9672799207e-08, /* 0x335557d2 */
35 s01  =  1.9153760746e-02, /* 0x3c9ce859 */
36 s02  =  1.8594678841e-04, /* 0x3942fab6 */
37 s03  =  1.1771846857e-06, /* 0x359dffc2 */
38 s04  =  5.0463624390e-09, /* 0x31ad6446 */
39 s05  =  1.2354227016e-11; /* 0x2d59567e */
40 
41 static const float zero    = 0.0;
42 
43 float
44 __ieee754_j1f(float x)
45 {
46 	float z, s,c,ss,cc,r,u,v,y;
47 	int32_t hx,ix;
48 
49 	GET_FLOAT_WORD(hx,x);
50 	ix = hx&0x7fffffff;
51 	if(ix>=0x7f800000) return one/x;
52 	y = fabsf(x);
53 	if(ix >= 0x40000000) {	/* |x| >= 2.0 */
54 		s = sinf(y);
55 		c = cosf(y);
56 		ss = -s-c;
57 		cc = s-c;
58 		if(ix<0x7f000000) {  /* make sure y+y not overflow */
59 		    z = cosf(y+y);
60 		    if ((s*c)>zero) cc = z/ss;
61 		    else 	    ss = z/cc;
62 		}
63 	/*
64 	 * j1(x) = 1/sqrt(pi) * (P(1,x)*cc - Q(1,x)*ss) / sqrt(x)
65 	 * y1(x) = 1/sqrt(pi) * (P(1,x)*ss + Q(1,x)*cc) / sqrt(x)
66 	 */
67 		if(ix>0x80000000) z = (invsqrtpi*cc)/sqrtf(y);
68 		else {
69 		    u = ponef(y); v = qonef(y);
70 		    z = invsqrtpi*(u*cc-v*ss)/sqrtf(y);
71 		}
72 		if(hx<0) return -z;
73 		else  	 return  z;
74 	}
75 	if(ix<0x32000000) {	/* |x|<2**-27 */
76 	    if(huge+x>one) return (float)0.5*x;/* inexact if x!=0 necessary */
77 	}
78 	z = x*x;
79 	r =  z*(r00+z*(r01+z*(r02+z*r03)));
80 	s =  one+z*(s01+z*(s02+z*(s03+z*(s04+z*s05))));
81 	r *= x;
82 	return(x*(float)0.5+r/s);
83 }
84 
85 static const float U0[5] = {
86  -1.9605709612e-01, /* 0xbe48c331 */
87   5.0443872809e-02, /* 0x3d4e9e3c */
88  -1.9125689287e-03, /* 0xbafaaf2a */
89   2.3525259166e-05, /* 0x37c5581c */
90  -9.1909917899e-08, /* 0xb3c56003 */
91 };
92 static const float V0[5] = {
93   1.9916731864e-02, /* 0x3ca3286a */
94   2.0255257550e-04, /* 0x3954644b */
95   1.3560879779e-06, /* 0x35b602d4 */
96   6.2274145840e-09, /* 0x31d5f8eb */
97   1.6655924903e-11, /* 0x2d9281cf */
98 };
99 
100 float
101 __ieee754_y1f(float x)
102 {
103 	float z, s,c,ss,cc,u,v;
104 	int32_t hx,ix;
105 
106 	GET_FLOAT_WORD(hx,x);
107         ix = 0x7fffffff&hx;
108     /* if Y1(NaN) is NaN, Y1(-inf) is NaN, Y1(inf) is 0 */
109 	if(ix>=0x7f800000) return  one/(x+x*x);
110         if(ix==0) return -one/zero;
111         if(hx<0) return zero/zero;
112         if(ix >= 0x40000000) {  /* |x| >= 2.0 */
113                 s = sinf(x);
114                 c = cosf(x);
115                 ss = -s-c;
116                 cc = s-c;
117                 if(ix<0x7f000000) {  /* make sure x+x not overflow */
118                     z = cosf(x+x);
119                     if ((s*c)>zero) cc = z/ss;
120                     else            ss = z/cc;
121                 }
122         /* y1(x) = sqrt(2/(pi*x))*(p1(x)*sin(x0)+q1(x)*cos(x0))
123          * where x0 = x-3pi/4
124          *      Better formula:
125          *              cos(x0) = cos(x)cos(3pi/4)+sin(x)sin(3pi/4)
126          *                      =  1/sqrt(2) * (sin(x) - cos(x))
127          *              sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4)
128          *                      = -1/sqrt(2) * (cos(x) + sin(x))
129          * To avoid cancellation, use
130          *              sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
131          * to compute the worse one.
132          */
133                 if(ix>0x48000000) z = (invsqrtpi*ss)/sqrtf(x);
134                 else {
135                     u = ponef(x); v = qonef(x);
136                     z = invsqrtpi*(u*ss+v*cc)/sqrtf(x);
137                 }
138                 return z;
139         }
140         if(ix<=0x24800000) {    /* x < 2**-54 */
141             return(-tpi/x);
142         }
143         z = x*x;
144         u = U0[0]+z*(U0[1]+z*(U0[2]+z*(U0[3]+z*U0[4])));
145         v = one+z*(V0[0]+z*(V0[1]+z*(V0[2]+z*(V0[3]+z*V0[4]))));
146         return(x*(u/v) + tpi*(__ieee754_j1f(x)*__ieee754_logf(x)-one/x));
147 }
148 
149 /* For x >= 8, the asymptotic expansions of pone is
150  *	1 + 15/128 s^2 - 4725/2^15 s^4 - ...,	where s = 1/x.
151  * We approximate pone by
152  * 	pone(x) = 1 + (R/S)
153  * where  R = pr0 + pr1*s^2 + pr2*s^4 + ... + pr5*s^10
154  * 	  S = 1 + ps0*s^2 + ... + ps4*s^10
155  * and
156  *	| pone(x)-1-R/S | <= 2  ** ( -60.06)
157  */
158 
159 static const float pr8[6] = { /* for x in [inf, 8]=1/[0,0.125] */
160   0.0000000000e+00, /* 0x00000000 */
161   1.1718750000e-01, /* 0x3df00000 */
162   1.3239480972e+01, /* 0x4153d4ea */
163   4.1205184937e+02, /* 0x43ce06a3 */
164   3.8747453613e+03, /* 0x45722bed */
165   7.9144794922e+03, /* 0x45f753d6 */
166 };
167 static const float ps8[5] = {
168   1.1420736694e+02, /* 0x42e46a2c */
169   3.6509309082e+03, /* 0x45642ee5 */
170   3.6956207031e+04, /* 0x47105c35 */
171   9.7602796875e+04, /* 0x47bea166 */
172   3.0804271484e+04, /* 0x46f0a88b */
173 };
174 
175 static const float pr5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */
176   1.3199052094e-11, /* 0x2d68333f */
177   1.1718749255e-01, /* 0x3defffff */
178   6.8027510643e+00, /* 0x40d9b023 */
179   1.0830818176e+02, /* 0x42d89dca */
180   5.1763616943e+02, /* 0x440168b7 */
181   5.2871520996e+02, /* 0x44042dc6 */
182 };
183 static const float ps5[5] = {
184   5.9280597687e+01, /* 0x426d1f55 */
185   9.9140142822e+02, /* 0x4477d9b1 */
186   5.3532670898e+03, /* 0x45a74a23 */
187   7.8446904297e+03, /* 0x45f52586 */
188   1.5040468750e+03, /* 0x44bc0180 */
189 };
190 
191 static const float pr3[6] = {
192   3.0250391081e-09, /* 0x314fe10d */
193   1.1718686670e-01, /* 0x3defffab */
194   3.9329774380e+00, /* 0x407bb5e7 */
195   3.5119403839e+01, /* 0x420c7a45 */
196   9.1055007935e+01, /* 0x42b61c2a */
197   4.8559066772e+01, /* 0x42423c7c */
198 };
199 static const float ps3[5] = {
200   3.4791309357e+01, /* 0x420b2a4d */
201   3.3676245117e+02, /* 0x43a86198 */
202   1.0468714600e+03, /* 0x4482dbe3 */
203   8.9081134033e+02, /* 0x445eb3ed */
204   1.0378793335e+02, /* 0x42cf936c */
205 };
206 
207 static const float pr2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */
208   1.0771083225e-07, /* 0x33e74ea8 */
209   1.1717621982e-01, /* 0x3deffa16 */
210   2.3685150146e+00, /* 0x401795c0 */
211   1.2242610931e+01, /* 0x4143e1bc */
212   1.7693971634e+01, /* 0x418d8d41 */
213   5.0735230446e+00, /* 0x40a25a4d */
214 };
215 static const float ps2[5] = {
216   2.1436485291e+01, /* 0x41ab7dec */
217   1.2529022980e+02, /* 0x42fa9499 */
218   2.3227647400e+02, /* 0x436846c7 */
219   1.1767937469e+02, /* 0x42eb5bd7 */
220   8.3646392822e+00, /* 0x4105d590 */
221 };
222 
223 	static float ponef(float x)
224 {
225 	const float *p,*q;
226 	float z,r,s;
227         int32_t ix;
228 	GET_FLOAT_WORD(ix,x);
229 	ix &= 0x7fffffff;
230         if(ix>=0x41000000)     {p = pr8; q= ps8;}
231         else if(ix>=0x40f71c58){p = pr5; q= ps5;}
232         else if(ix>=0x4036db68){p = pr3; q= ps3;}
233         else if(ix>=0x40000000){p = pr2; q= ps2;}
234         z = one/(x*x);
235         r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))));
236         s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4]))));
237         return one+ r/s;
238 }
239 
240 
241 /* For x >= 8, the asymptotic expansions of qone is
242  *	3/8 s - 105/1024 s^3 - ..., where s = 1/x.
243  * We approximate pone by
244  * 	qone(x) = s*(0.375 + (R/S))
245  * where  R = qr1*s^2 + qr2*s^4 + ... + qr5*s^10
246  * 	  S = 1 + qs1*s^2 + ... + qs6*s^12
247  * and
248  *	| qone(x)/s -0.375-R/S | <= 2  ** ( -61.13)
249  */
250 
251 static const float qr8[6] = { /* for x in [inf, 8]=1/[0,0.125] */
252   0.0000000000e+00, /* 0x00000000 */
253  -1.0253906250e-01, /* 0xbdd20000 */
254  -1.6271753311e+01, /* 0xc1822c8d */
255  -7.5960174561e+02, /* 0xc43de683 */
256  -1.1849806641e+04, /* 0xc639273a */
257  -4.8438511719e+04, /* 0xc73d3683 */
258 };
259 static const float qs8[6] = {
260   1.6139537048e+02, /* 0x43216537 */
261   7.8253862305e+03, /* 0x45f48b17 */
262   1.3387534375e+05, /* 0x4802bcd6 */
263   7.1965775000e+05, /* 0x492fb29c */
264   6.6660125000e+05, /* 0x4922be94 */
265  -2.9449025000e+05, /* 0xc88fcb48 */
266 };
267 
268 static const float qr5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */
269  -2.0897993405e-11, /* 0xadb7d219 */
270  -1.0253904760e-01, /* 0xbdd1fffe */
271  -8.0564479828e+00, /* 0xc100e736 */
272  -1.8366960144e+02, /* 0xc337ab6b */
273  -1.3731937256e+03, /* 0xc4aba633 */
274  -2.6124443359e+03, /* 0xc523471c */
275 };
276 static const float qs5[6] = {
277   8.1276550293e+01, /* 0x42a28d98 */
278   1.9917987061e+03, /* 0x44f8f98f */
279   1.7468484375e+04, /* 0x468878f8 */
280   4.9851425781e+04, /* 0x4742bb6d */
281   2.7948074219e+04, /* 0x46da5826 */
282  -4.7191835938e+03, /* 0xc5937978 */
283 };
284 
285 static const float qr3[6] = {
286  -5.0783124372e-09, /* 0xb1ae7d4f */
287  -1.0253783315e-01, /* 0xbdd1ff5b */
288  -4.6101160049e+00, /* 0xc0938612 */
289  -5.7847221375e+01, /* 0xc267638e */
290  -2.2824453735e+02, /* 0xc3643e9a */
291  -2.1921012878e+02, /* 0xc35b35cb */
292 };
293 static const float qs3[6] = {
294   4.7665153503e+01, /* 0x423ea91e */
295   6.7386511230e+02, /* 0x4428775e */
296   3.3801528320e+03, /* 0x45534272 */
297   5.5477290039e+03, /* 0x45ad5dd5 */
298   1.9031191406e+03, /* 0x44ede3d0 */
299  -1.3520118713e+02, /* 0xc3073381 */
300 };
301 
302 static const float qr2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */
303  -1.7838172539e-07, /* 0xb43f8932 */
304  -1.0251704603e-01, /* 0xbdd1f475 */
305  -2.7522056103e+00, /* 0xc0302423 */
306  -1.9663616180e+01, /* 0xc19d4f16 */
307  -4.2325313568e+01, /* 0xc2294d1f */
308  -2.1371921539e+01, /* 0xc1aaf9b2 */
309 };
310 static const float qs2[6] = {
311   2.9533363342e+01, /* 0x41ec4454 */
312   2.5298155212e+02, /* 0x437cfb47 */
313   7.5750280762e+02, /* 0x443d602e */
314   7.3939318848e+02, /* 0x4438d92a */
315   1.5594900513e+02, /* 0x431bf2f2 */
316  -4.9594988823e+00, /* 0xc09eb437 */
317 };
318 
319 	static float qonef(float x)
320 {
321 	const float *p,*q;
322 	float  s,r,z;
323 	int32_t ix;
324 	GET_FLOAT_WORD(ix,x);
325 	ix &= 0x7fffffff;
326 	if(ix>=0x40200000)     {p = qr8; q= qs8;}
327 	else if(ix>=0x40f71c58){p = qr5; q= qs5;}
328 	else if(ix>=0x4036db68){p = qr3; q= qs3;}
329 	else if(ix>=0x40000000){p = qr2; q= qs2;}
330 	z = one/(x*x);
331 	r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))));
332 	s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5])))));
333 	return ((float).375 + r/s)/x;
334 }
335