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Side by Side Diff: fusl/src/math/jnf.c

Issue 1714623002: [fusl] clang-format fusl (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: headers too Created 4 years, 10 months ago
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1 /* origin: FreeBSD /usr/src/lib/msun/src/e_jnf.c */ 1 /* origin: FreeBSD /usr/src/lib/msun/src/e_jnf.c */
2 /* 2 /*
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 */ 4 */
5 /* 5 /*
6 * ==================================================== 6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 * 8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business. 9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this 10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice 11 * software is freely granted, provided that this notice
12 * is preserved. 12 * is preserved.
13 * ==================================================== 13 * ====================================================
14 */ 14 */
15 15
16 #define _GNU_SOURCE 16 #define _GNU_SOURCE
17 #include "libm.h" 17 #include "libm.h"
18 18
19 float jnf(int n, float x) 19 float jnf(int n, float x) {
20 { 20 uint32_t ix;
21 » uint32_t ix; 21 int nm1, sign, i;
22 » int nm1, sign, i; 22 float a, b, temp;
23 » float a, b, temp;
24 23
25 » GET_FLOAT_WORD(ix, x); 24 GET_FLOAT_WORD(ix, x);
26 » sign = ix>>31; 25 sign = ix >> 31;
27 » ix &= 0x7fffffff; 26 ix &= 0x7fffffff;
28 » if (ix > 0x7f800000) /* nan */ 27 if (ix > 0x7f800000) /* nan */
29 » » return x; 28 return x;
30 29
31 » /* J(-n,x) = J(n,-x), use |n|-1 to avoid overflow in -n */ 30 /* J(-n,x) = J(n,-x), use |n|-1 to avoid overflow in -n */
32 » if (n == 0) 31 if (n == 0)
33 » » return j0f(x); 32 return j0f(x);
34 » if (n < 0) { 33 if (n < 0) {
35 » » nm1 = -(n+1); 34 nm1 = -(n + 1);
36 » » x = -x; 35 x = -x;
37 » » sign ^= 1; 36 sign ^= 1;
38 » } else 37 } else
39 » » nm1 = n-1; 38 nm1 = n - 1;
40 » if (nm1 == 0) 39 if (nm1 == 0)
41 » » return j1f(x); 40 return j1f(x);
42 41
43 » sign &= n; /* even n: 0, odd n: signbit(x) */ 42 sign &= n; /* even n: 0, odd n: signbit(x) */
44 » x = fabsf(x); 43 x = fabsf(x);
45 » if (ix == 0 || ix == 0x7f800000) /* if x is 0 or inf */ 44 if (ix == 0 || ix == 0x7f800000) /* if x is 0 or inf */
46 » » b = 0.0f; 45 b = 0.0f;
47 » else if (nm1 < x) { 46 else if (nm1 < x) {
48 » » /* Safe to use J(n+1,x)=2n/x *J(n,x)-J(n-1,x) */ 47 /* Safe to use J(n+1,x)=2n/x *J(n,x)-J(n-1,x) */
49 » » a = j0f(x); 48 a = j0f(x);
50 » » b = j1f(x); 49 b = j1f(x);
51 » » for (i=0; i<nm1; ){ 50 for (i = 0; i < nm1;) {
52 » » » i++; 51 i++;
53 » » » temp = b; 52 temp = b;
54 » » » b = b*(2.0f*i/x) - a; 53 b = b * (2.0f * i / x) - a;
55 » » » a = temp; 54 a = temp;
56 » » } 55 }
57 » } else { 56 } else {
58 » » if (ix < 0x35800000) { /* x < 2**-20 */ 57 if (ix < 0x35800000) { /* x < 2**-20 */
59 » » » /* x is tiny, return the first Taylor expansion of J(n,x ) 58 /* x is tiny, return the first Taylor expansion of J(n,x)
60 » » » * J(n,x) = 1/n!*(x/2)^n - ... 59 * J(n,x) = 1/n!*(x/2)^n - ...
61 » » » */ 60 */
62 » » » if (nm1 > 8) /* underflow */ 61 if (nm1 > 8) /* underflow */
63 » » » » nm1 = 8; 62 nm1 = 8;
64 » » » temp = 0.5f * x; 63 temp = 0.5f * x;
65 » » » b = temp; 64 b = temp;
66 » » » a = 1.0f; 65 a = 1.0f;
67 » » » for (i=2; i<=nm1+1; i++) { 66 for (i = 2; i <= nm1 + 1; i++) {
68 » » » » a *= (float)i; /* a = n! */ 67 a *= (float)i; /* a = n! */
69 » » » » b *= temp; /* b = (x/2)^n */ 68 b *= temp; /* b = (x/2)^n */
70 » » » } 69 }
71 » » » b = b/a; 70 b = b / a;
72 » » } else { 71 } else {
73 » » » /* use backward recurrence */ 72 /* use backward recurrence */
74 » » » /* x x^2 x^2 73 /* x x^2 x^2
75 » » » * J(n,x)/J(n-1,x) = ---- ------ ------ ..... 74 * J(n,x)/J(n-1,x) = ---- ------ ------ .....
76 » » » * 2n - 2(n+1) - 2(n+2) 75 * 2n - 2(n+1) - 2(n+2)
77 » » » * 76 *
78 » » » * 1 1 1 77 * 1 1 1
79 » » » * (for large x) = ---- ------ ------ ..... 78 * (for large x) = ---- ------ ------ .....
80 » » » * 2n 2(n+1) 2(n+2) 79 * 2n 2(n+1) 2(n+2)
81 » » » * -- - ------ - ------ - 80 * -- - ------ - ------ -
82 » » » * x x x 81 * x x x
83 » » » * 82 *
84 » » » * Let w = 2n/x and h=2/x, then the above quotient 83 * Let w = 2n/x and h=2/x, then the above quotient
85 » » » * is equal to the continued fraction: 84 * is equal to the continued fraction:
86 » » » * 1 85 * 1
87 » » » * = ----------------------- 86 * = -----------------------
88 » » » * 1 87 * 1
89 » » » * w - ----------------- 88 * w - -----------------
90 » » » * 1 89 * 1
91 » » » * w+h - --------- 90 * w+h - ---------
92 » » » * w+2h - ... 91 * w+2h - ...
93 » » » * 92 *
94 » » » * To determine how many terms needed, let 93 * To determine how many terms needed, let
95 » » » * Q(0) = w, Q(1) = w(w+h) - 1, 94 * Q(0) = w, Q(1) = w(w+h) - 1,
96 » » » * Q(k) = (w+k*h)*Q(k-1) - Q(k-2), 95 * Q(k) = (w+k*h)*Q(k-1) - Q(k-2),
97 » » » * When Q(k) > 1e4 good for single 96 * When Q(k) > 1e4 good for single
98 » » » * When Q(k) > 1e9 good for double 97 * When Q(k) > 1e9 good for double
99 » » » * When Q(k) > 1e17 good for quadruple 98 * When Q(k) > 1e17 good for quadruple
100 » » » */ 99 */
101 » » » /* determine k */ 100 /* determine k */
102 » » » float t,q0,q1,w,h,z,tmp,nf; 101 float t, q0, q1, w, h, z, tmp, nf;
103 » » » int k; 102 int k;
104 103
105 » » » nf = nm1+1.0f; 104 nf = nm1 + 1.0f;
106 » » » w = 2*nf/x; 105 w = 2 * nf / x;
107 » » » h = 2/x; 106 h = 2 / x;
108 » » » z = w+h; 107 z = w + h;
109 » » » q0 = w; 108 q0 = w;
110 » » » q1 = w*z - 1.0f; 109 q1 = w * z - 1.0f;
111 » » » k = 1; 110 k = 1;
112 » » » while (q1 < 1.0e4f) { 111 while (q1 < 1.0e4f) {
113 » » » » k += 1; 112 k += 1;
114 » » » » z += h; 113 z += h;
115 » » » » tmp = z*q1 - q0; 114 tmp = z * q1 - q0;
116 » » » » q0 = q1; 115 q0 = q1;
117 » » » » q1 = tmp; 116 q1 = tmp;
118 » » » } 117 }
119 » » » for (t=0.0f, i=k; i>=0; i--) 118 for (t = 0.0f, i = k; i >= 0; i--)
120 » » » » t = 1.0f/(2*(i+nf)/x-t); 119 t = 1.0f / (2 * (i + nf) / x - t);
121 » » » a = t; 120 a = t;
122 » » » b = 1.0f; 121 b = 1.0f;
123 » » » /* estimate log((2/x)^n*n!) = n*log(2/x)+n*ln(n) 122 /* estimate log((2/x)^n*n!) = n*log(2/x)+n*ln(n)
124 » » » * Hence, if n*(log(2n/x)) > ... 123 * Hence, if n*(log(2n/x)) > ...
125 » » » * single 8.8722839355e+01 124 * single 8.8722839355e+01
126 » » » * double 7.09782712893383973096e+02 125 * double 7.09782712893383973096e+02
127 » » » * long double 1.13565234062941439494919310779707650061 70e+04 126 * long double 1.1356523406294143949491931077970765006170e+04
128 » » » * then recurrent value may overflow and the result is 127 * then recurrent value may overflow and the result is
129 » » » * likely underflow to zero 128 * likely underflow to zero
130 » » » */ 129 */
131 » » » tmp = nf*logf(fabsf(w)); 130 tmp = nf * logf(fabsf(w));
132 » » » if (tmp < 88.721679688f) { 131 if (tmp < 88.721679688f) {
133 » » » » for (i=nm1; i>0; i--) { 132 for (i = nm1; i > 0; i--) {
134 » » » » » temp = b; 133 temp = b;
135 » » » » » b = 2.0f*i*b/x - a; 134 b = 2.0f * i * b / x - a;
136 » » » » » a = temp; 135 a = temp;
137 » » » » } 136 }
138 » » » } else { 137 } else {
139 » » » » for (i=nm1; i>0; i--){ 138 for (i = nm1; i > 0; i--) {
140 » » » » » temp = b; 139 temp = b;
141 » » » » » b = 2.0f*i*b/x - a; 140 b = 2.0f * i * b / x - a;
142 » » » » » a = temp; 141 a = temp;
143 » » » » » /* scale b to avoid spurious overflow */ 142 /* scale b to avoid spurious overflow */
144 » » » » » if (b > 0x1p60f) { 143 if (b > 0x1p60f) {
145 » » » » » » a /= b; 144 a /= b;
146 » » » » » » t /= b; 145 t /= b;
147 » » » » » » b = 1.0f; 146 b = 1.0f;
148 » » » » » } 147 }
149 » » » » } 148 }
150 » » » } 149 }
151 » » » z = j0f(x); 150 z = j0f(x);
152 » » » w = j1f(x); 151 w = j1f(x);
153 » » » if (fabsf(z) >= fabsf(w)) 152 if (fabsf(z) >= fabsf(w))
154 » » » » b = t*z/b; 153 b = t * z / b;
155 » » » else 154 else
156 » » » » b = t*w/a; 155 b = t * w / a;
157 » » } 156 }
158 » } 157 }
159 » return sign ? -b : b; 158 return sign ? -b : b;
160 } 159 }
161 160
162 float ynf(int n, float x) 161 float ynf(int n, float x) {
163 { 162 uint32_t ix, ib;
164 » uint32_t ix, ib; 163 int nm1, sign, i;
165 » int nm1, sign, i; 164 float a, b, temp;
166 » float a, b, temp;
167 165
168 » GET_FLOAT_WORD(ix, x); 166 GET_FLOAT_WORD(ix, x);
169 » sign = ix>>31; 167 sign = ix >> 31;
170 » ix &= 0x7fffffff; 168 ix &= 0x7fffffff;
171 » if (ix > 0x7f800000) /* nan */ 169 if (ix > 0x7f800000) /* nan */
172 » » return x; 170 return x;
173 » if (sign && ix != 0) /* x < 0 */ 171 if (sign && ix != 0) /* x < 0 */
174 » » return 0/0.0f; 172 return 0 / 0.0f;
175 » if (ix == 0x7f800000) 173 if (ix == 0x7f800000)
176 » » return 0.0f; 174 return 0.0f;
177 175
178 » if (n == 0) 176 if (n == 0)
179 » » return y0f(x); 177 return y0f(x);
180 » if (n < 0) { 178 if (n < 0) {
181 » » nm1 = -(n+1); 179 nm1 = -(n + 1);
182 » » sign = n&1; 180 sign = n & 1;
183 » } else { 181 } else {
184 » » nm1 = n-1; 182 nm1 = n - 1;
185 » » sign = 0; 183 sign = 0;
186 » } 184 }
187 » if (nm1 == 0) 185 if (nm1 == 0)
188 » » return sign ? -y1f(x) : y1f(x); 186 return sign ? -y1f(x) : y1f(x);
189 187
190 » a = y0f(x); 188 a = y0f(x);
191 » b = y1f(x); 189 b = y1f(x);
192 » /* quit if b is -inf */ 190 /* quit if b is -inf */
193 » GET_FLOAT_WORD(ib,b); 191 GET_FLOAT_WORD(ib, b);
194 » for (i = 0; i < nm1 && ib != 0xff800000; ) { 192 for (i = 0; i < nm1 && ib != 0xff800000;) {
195 » » i++; 193 i++;
196 » » temp = b; 194 temp = b;
197 » » b = (2.0f*i/x)*b - a; 195 b = (2.0f * i / x) * b - a;
198 » » GET_FLOAT_WORD(ib, b); 196 GET_FLOAT_WORD(ib, b);
199 » » a = temp; 197 a = temp;
200 » } 198 }
201 » return sign ? -b : b; 199 return sign ? -b : b;
202 } 200 }
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