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Diffstat (limited to 'libm/double/iv.c')
-rw-r--r-- | libm/double/iv.c | 116 |
1 files changed, 0 insertions, 116 deletions
diff --git a/libm/double/iv.c b/libm/double/iv.c deleted file mode 100644 index ec0e96244..000000000 --- a/libm/double/iv.c +++ /dev/null @@ -1,116 +0,0 @@ -/* iv.c - * - * Modified Bessel function of noninteger order - * - * - * - * SYNOPSIS: - * - * double v, x, y, iv(); - * - * y = iv( v, x ); - * - * - * - * DESCRIPTION: - * - * Returns modified Bessel function of order v of the - * argument. If x is negative, v must be integer valued. - * - * The function is defined as Iv(x) = Jv( ix ). It is - * here computed in terms of the confluent hypergeometric - * function, according to the formula - * - * v -x - * Iv(x) = (x/2) e hyperg( v+0.5, 2v+1, 2x ) / gamma(v+1) - * - * If v is a negative integer, then v is replaced by -v. - * - * - * ACCURACY: - * - * Tested at random points (v, x), with v between 0 and - * 30, x between 0 and 28. - * Relative error: - * arithmetic domain # trials peak rms - * DEC 0,30 2000 3.1e-15 5.4e-16 - * IEEE 0,30 10000 1.7e-14 2.7e-15 - * - * Accuracy is diminished if v is near a negative integer. - * - * See also hyperg.c. - * - */ -/* iv.c */ -/* Modified Bessel function of noninteger order */ -/* If x < 0, then v must be an integer. */ - - -/* -Cephes Math Library Release 2.8: June, 2000 -Copyright 1984, 1987, 1988, 2000 by Stephen L. Moshier -*/ - - -#include <math.h> -#ifdef ANSIPROT -extern double hyperg ( double, double, double ); -extern double exp ( double ); -extern double gamma ( double ); -extern double log ( double ); -extern double fabs ( double ); -extern double floor ( double ); -#else -double hyperg(), exp(), gamma(), log(), fabs(), floor(); -#endif -extern double MACHEP, MAXNUM; - -double iv( v, x ) -double v, x; -{ -int sign; -double t, ax; - -/* If v is a negative integer, invoke symmetry */ -t = floor(v); -if( v < 0.0 ) - { - if( t == v ) - { - v = -v; /* symmetry */ - t = -t; - } - } -/* If x is negative, require v to be an integer */ -sign = 1; -if( x < 0.0 ) - { - if( t != v ) - { - mtherr( "iv", DOMAIN ); - return( 0.0 ); - } - if( v != 2.0 * floor(v/2.0) ) - sign = -1; - } - -/* Avoid logarithm singularity */ -if( x == 0.0 ) - { - if( v == 0.0 ) - return( 1.0 ); - if( v < 0.0 ) - { - mtherr( "iv", OVERFLOW ); - return( MAXNUM ); - } - else - return( 0.0 ); - } - -ax = fabs(x); -t = v * log( 0.5 * ax ) - x; -t = sign * exp(t) / gamma( v + 1.0 ); -ax = v + 0.5; -return( t * hyperg( ax, 2.0 * ax, 2.0 * x ) ); -} |