ESS_GUIESS_GUI_DocsESS_GUI_batch_fittingESS_GUI_bumps_abstractionESS_GUI_iss1116ESS_GUI_iss879ESS_GUI_iss959ESS_GUI_openclESS_GUI_orderingESS_GUI_sync_sascalccostrafo411magnetic_scattrelease-4.1.1release-4.1.2release-4.2.2release_4.0.1ticket-1009ticket-1094-headlessticket-1242-2d-resolutionticket-1243ticket-1249ticket885unittest-saveload
|
Last change
on this file since 8bea1519 was
79492222,
checked in by krzywon, 10 years ago
|
|
Changed the file and folder names to remove all SANS references.
|
-
Property mode set to
100644
|
|
File size:
1.8 KB
|
| Rev | Line | |
|---|
| [230f479] | 1 | /* yn.c |
|---|
| 2 | * |
|---|
| 3 | * Bessel function of second kind of integer order |
|---|
| 4 | * |
|---|
| 5 | * |
|---|
| 6 | * |
|---|
| 7 | * SYNOPSIS: |
|---|
| 8 | * |
|---|
| 9 | * double x, y, yn(); |
|---|
| 10 | * int n; |
|---|
| 11 | * |
|---|
| 12 | * y = yn( n, x ); |
|---|
| 13 | * |
|---|
| 14 | * |
|---|
| 15 | * |
|---|
| 16 | * DESCRIPTION: |
|---|
| 17 | * |
|---|
| 18 | * Returns Bessel function of order n, where n is a |
|---|
| 19 | * (possibly negative) integer. |
|---|
| 20 | * |
|---|
| 21 | * The function is evaluated by forward recurrence on |
|---|
| 22 | * n, starting with values computed by the routines |
|---|
| 23 | * y0() and y1(). |
|---|
| 24 | * |
|---|
| 25 | * If n = 0 or 1 the routine for y0 or y1 is called |
|---|
| 26 | * directly. |
|---|
| 27 | * |
|---|
| 28 | * |
|---|
| 29 | * |
|---|
| 30 | * ACCURACY: |
|---|
| 31 | * |
|---|
| 32 | * |
|---|
| 33 | * Absolute error, except relative |
|---|
| 34 | * when y > 1: |
|---|
| 35 | * arithmetic domain # trials peak rms |
|---|
| 36 | * DEC 0, 30 2200 2.9e-16 5.3e-17 |
|---|
| 37 | * IEEE 0, 30 30000 3.4e-15 4.3e-16 |
|---|
| 38 | * |
|---|
| 39 | * |
|---|
| 40 | * ERROR MESSAGES: |
|---|
| 41 | * |
|---|
| 42 | * message condition value returned |
|---|
| 43 | * yn singularity x = 0 MAXNUM |
|---|
| 44 | * yn overflow MAXNUM |
|---|
| 45 | * |
|---|
| 46 | * Spot checked against tables for x, n between 0 and 100. |
|---|
| 47 | * |
|---|
| 48 | */ |
|---|
| 49 | |
|---|
| 50 | /* |
|---|
| 51 | Cephes Math Library Release 2.8: June, 2000 |
|---|
| 52 | Copyright 1984, 1987, 2000 by Stephen L. Moshier |
|---|
| 53 | */ |
|---|
| 54 | |
|---|
| 55 | #include "mconf.h" |
|---|
| 56 | #ifdef ANSIPROT |
|---|
| 57 | extern double y0 ( double ); |
|---|
| 58 | extern double y1 ( double ); |
|---|
| 59 | extern double log ( double ); |
|---|
| 60 | #else |
|---|
| 61 | double y0(), y1(), log(); |
|---|
| 62 | #endif |
|---|
| 63 | extern double MAXNUM, MAXLOG; |
|---|
| 64 | |
|---|
| 65 | double yn( n, x ) |
|---|
| 66 | int n; |
|---|
| 67 | double x; |
|---|
| 68 | { |
|---|
| 69 | double an, anm1, anm2, r; |
|---|
| 70 | int k, sign; |
|---|
| 71 | |
|---|
| 72 | if( n < 0 ) |
|---|
| 73 | { |
|---|
| 74 | n = -n; |
|---|
| 75 | if( (n & 1) == 0 ) /* -1**n */ |
|---|
| 76 | sign = 1; |
|---|
| 77 | else |
|---|
| 78 | sign = -1; |
|---|
| 79 | } |
|---|
| 80 | else |
|---|
| 81 | sign = 1; |
|---|
| 82 | |
|---|
| 83 | |
|---|
| 84 | if( n == 0 ) |
|---|
| 85 | return( sign * y0(x) ); |
|---|
| 86 | if( n == 1 ) |
|---|
| 87 | return( sign * y1(x) ); |
|---|
| 88 | |
|---|
| 89 | /* test for overflow */ |
|---|
| 90 | if( x <= 0.0 ) |
|---|
| 91 | { |
|---|
| 92 | mtherr( "yn", SING ); |
|---|
| 93 | return( -MAXNUM ); |
|---|
| 94 | } |
|---|
| 95 | |
|---|
| 96 | /* forward recurrence on n */ |
|---|
| 97 | |
|---|
| 98 | anm2 = y0(x); |
|---|
| 99 | anm1 = y1(x); |
|---|
| 100 | k = 1; |
|---|
| 101 | r = 2 * k; |
|---|
| 102 | do |
|---|
| 103 | { |
|---|
| 104 | an = r * anm1 / x - anm2; |
|---|
| 105 | anm2 = anm1; |
|---|
| 106 | anm1 = an; |
|---|
| 107 | r += 2.0; |
|---|
| 108 | ++k; |
|---|
| 109 | } |
|---|
| 110 | while( k < n ); |
|---|
| 111 | |
|---|
| 112 | |
|---|
| 113 | return( sign * an ); |
|---|
| 114 | } |
|---|
Note: See
TracBrowser
for help on using the repository browser.
