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authorEric Andersen <andersen@codepoet.org>2001-11-22 14:04:29 +0000
committerEric Andersen <andersen@codepoet.org>2001-11-22 14:04:29 +0000
commit7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 (patch)
tree3a7e8476e868ae15f4da1b7ce26b2db6f434468c /libm/float/igamif.c
parentc117dd5fb183afb1a4790a6f6110d88704be6bf8 (diff)
Totally rework the math library, this time based on the MacOs X
math library (which is itself based on the math lib from FreeBSD). -Erik
Diffstat (limited to 'libm/float/igamif.c')
-rw-r--r--libm/float/igamif.c112
1 files changed, 0 insertions, 112 deletions
diff --git a/libm/float/igamif.c b/libm/float/igamif.c
deleted file mode 100644
index 5a33b4982..000000000
--- a/libm/float/igamif.c
+++ /dev/null
@@ -1,112 +0,0 @@
-/* igamif()
- *
- * Inverse of complemented imcomplete gamma integral
- *
- *
- *
- * SYNOPSIS:
- *
- * float a, x, y, igamif();
- *
- * x = igamif( a, y );
- *
- *
- *
- * DESCRIPTION:
- *
- * Given y, the function finds x such that
- *
- * igamc( a, x ) = y.
- *
- * Starting with the approximate value
- *
- * 3
- * x = a t
- *
- * where
- *
- * t = 1 - d - ndtri(y) sqrt(d)
- *
- * and
- *
- * d = 1/9a,
- *
- * the routine performs up to 10 Newton iterations to find the
- * root of igamc(a,x) - y = 0.
- *
- *
- * ACCURACY:
- *
- * Tested for a ranging from 0 to 100 and x from 0 to 1.
- *
- * Relative error:
- * arithmetic domain # trials peak rms
- * IEEE 0,100 5000 1.0e-5 1.5e-6
- *
- */
-
-/*
-Cephes Math Library Release 2.2: July, 1992
-Copyright 1984, 1987, 1992 by Stephen L. Moshier
-Direct inquiries to 30 Frost Street, Cambridge, MA 02140
-*/
-
-#include <math.h>
-
-extern float MACHEPF, MAXLOGF;
-
-#define fabsf(x) ( (x) < 0 ? -(x) : (x) )
-
-#ifdef ANSIC
-float igamcf(float, float);
-float ndtrif(float), expf(float), logf(float), sqrtf(float), lgamf(float);
-#else
-float igamcf();
-float ndtrif(), expf(), logf(), sqrtf(), lgamf();
-#endif
-
-
-float igamif( float aa, float yy0 )
-{
-float a, y0, d, y, x0, lgm;
-int i;
-
-a = aa;
-y0 = yy0;
-/* approximation to inverse function */
-d = 1.0/(9.0*a);
-y = ( 1.0 - d - ndtrif(y0) * sqrtf(d) );
-x0 = a * y * y * y;
-
-lgm = lgamf(a);
-
-for( i=0; i<10; i++ )
- {
- if( x0 <= 0.0 )
- {
- mtherr( "igamif", UNDERFLOW );
- return(0.0);
- }
- y = igamcf(a,x0);
-/* compute the derivative of the function at this point */
- d = (a - 1.0) * logf(x0) - x0 - lgm;
- if( d < -MAXLOGF )
- {
- mtherr( "igamif", UNDERFLOW );
- goto done;
- }
- d = -expf(d);
-/* compute the step to the next approximation of x */
- if( d == 0.0 )
- goto done;
- d = (y - y0)/d;
- x0 = x0 - d;
- if( i < 3 )
- continue;
- if( fabsf(d/x0) < (2.0 * MACHEPF) )
- goto done;
- }
-
-done:
-return( x0 );
-}