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
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
|
/* struve.c
*
* Struve function
*
*
*
* SYNOPSIS:
*
* double v, x, y, struve();
*
* y = struve( v, x );
*
*
*
* DESCRIPTION:
*
* Computes the Struve function Hv(x) of order v, argument x.
* Negative x is rejected unless v is an integer.
*
* This module also contains the hypergeometric functions 1F2
* and 3F0 and a routine for the Bessel function Yv(x) with
* noninteger v.
*
*
*
* ACCURACY:
*
* Not accurately characterized, but spot checked against tables.
*
*/
/*
Cephes Math Library Release 2.81: June, 2000
Copyright 1984, 1987, 1989, 2000 by Stephen L. Moshier
*/
#include <math.h>
#define DEBUG 0
#ifdef ANSIPROT
extern double gamma ( double );
extern double pow ( double, double );
extern double sqrt ( double );
extern double yn ( int, double );
extern double jv ( double, double );
extern double fabs ( double );
extern double floor ( double );
extern double sin ( double );
extern double cos ( double );
double yv ( double, double );
double onef2 (double, double, double, double, double * );
double threef0 (double, double, double, double, double * );
#else
double gamma(), pow(), sqrt(), yn(), yv(), jv(), fabs(), floor();
double sin(), cos();
double onef2(), threef0();
#endif
static double stop = 1.37e-17;
extern double MACHEP;
double onef2( a, b, c, x, err )
double a, b, c, x;
double *err;
{
double n, a0, sum, t;
double an, bn, cn, max, z;
an = a;
bn = b;
cn = c;
a0 = 1.0;
sum = 1.0;
n = 1.0;
t = 1.0;
max = 0.0;
do
{
if( an == 0 )
goto done;
if( bn == 0 )
goto error;
if( cn == 0 )
goto error;
if( (a0 > 1.0e34) || (n > 200) )
goto error;
a0 *= (an * x) / (bn * cn * n);
sum += a0;
an += 1.0;
bn += 1.0;
cn += 1.0;
n += 1.0;
z = fabs( a0 );
if( z > max )
max = z;
if( sum != 0 )
t = fabs( a0 / sum );
else
t = z;
}
while( t > stop );
done:
*err = fabs( MACHEP*max /sum );
#if DEBUG
printf(" onef2 cancellation error %.5E\n", *err );
#endif
goto xit;
error:
#if DEBUG
printf("onef2 does not converge\n");
#endif
*err = 1.0e38;
xit:
#if DEBUG
printf("onef2( %.2E %.2E %.2E %.5E ) = %.3E %.6E\n", a, b, c, x, n, sum);
#endif
return(sum);
}
double threef0( a, b, c, x, err )
double a, b, c, x;
double *err;
{
double n, a0, sum, t, conv, conv1;
double an, bn, cn, max, z;
an = a;
bn = b;
cn = c;
a0 = 1.0;
sum = 1.0;
n = 1.0;
t = 1.0;
max = 0.0;
conv = 1.0e38;
conv1 = conv;
do
{
if( an == 0.0 )
goto done;
if( bn == 0.0 )
goto done;
if( cn == 0.0 )
goto done;
if( (a0 > 1.0e34) || (n > 200) )
goto error;
a0 *= (an * bn * cn * x) / n;
an += 1.0;
bn += 1.0;
cn += 1.0;
n += 1.0;
z = fabs( a0 );
if( z > max )
max = z;
if( z >= conv )
{
if( (z < max) && (z > conv1) )
goto done;
}
conv1 = conv;
conv = z;
sum += a0;
if( sum != 0 )
t = fabs( a0 / sum );
else
t = z;
}
while( t > stop );
done:
t = fabs( MACHEP*max/sum );
#if DEBUG
printf(" threef0 cancellation error %.5E\n", t );
#endif
max = fabs( conv/sum );
if( max > t )
t = max;
#if DEBUG
printf(" threef0 convergence %.5E\n", max );
#endif
goto xit;
error:
#if DEBUG
printf("threef0 does not converge\n");
#endif
t = 1.0e38;
xit:
#if DEBUG
printf("threef0( %.2E %.2E %.2E %.5E ) = %.3E %.6E\n", a, b, c, x, n, sum);
#endif
*err = t;
return(sum);
}
extern double PI;
double struve( v, x )
double v, x;
{
double y, ya, f, g, h, t;
double onef2err, threef0err;
f = floor(v);
if( (v < 0) && ( v-f == 0.5 ) )
{
y = jv( -v, x );
f = 1.0 - f;
g = 2.0 * floor(f/2.0);
if( g != f )
y = -y;
return(y);
}
t = 0.25*x*x;
f = fabs(x);
g = 1.5 * fabs(v);
if( (f > 30.0) && (f > g) )
{
onef2err = 1.0e38;
y = 0.0;
}
else
{
y = onef2( 1.0, 1.5, 1.5+v, -t, &onef2err );
}
if( (f < 18.0) || (x < 0.0) )
{
threef0err = 1.0e38;
ya = 0.0;
}
else
{
ya = threef0( 1.0, 0.5, 0.5-v, -1.0/t, &threef0err );
}
f = sqrt( PI );
h = pow( 0.5*x, v-1.0 );
if( onef2err <= threef0err )
{
g = gamma( v + 1.5 );
y = y * h * t / ( 0.5 * f * g );
return(y);
}
else
{
g = gamma( v + 0.5 );
ya = ya * h / ( f * g );
ya = ya + yv( v, x );
return(ya);
}
}
/* Bessel function of noninteger order
*/
double yv( v, x )
double v, x;
{
double y, t;
int n;
y = floor( v );
if( y == v )
{
n = v;
y = yn( n, x );
return( y );
}
t = PI * v;
y = (cos(t) * jv( v, x ) - jv( -v, x ))/sin(t);
return( y );
}
/* Crossover points between ascending series and asymptotic series
* for Struve function
*
* v x
*
* 0 19.2
* 1 18.95
* 2 19.15
* 3 19.3
* 5 19.7
* 10 21.35
* 20 26.35
* 30 32.31
* 40 40.0
*/
|
