summaryrefslogtreecommitdiff
path: root/libm/ldouble/powil.c
diff options
context:
space:
mode:
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/ldouble/powil.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/ldouble/powil.c')
-rw-r--r--libm/ldouble/powil.c164
1 files changed, 0 insertions, 164 deletions
diff --git a/libm/ldouble/powil.c b/libm/ldouble/powil.c
deleted file mode 100644
index d36c7854e..000000000
--- a/libm/ldouble/powil.c
+++ /dev/null
@@ -1,164 +0,0 @@
-/* powil.c
- *
- * Real raised to integer power, long double precision
- *
- *
- *
- * SYNOPSIS:
- *
- * long double x, y, powil();
- * int n;
- *
- * y = powil( x, n );
- *
- *
- *
- * DESCRIPTION:
- *
- * Returns argument x raised to the nth power.
- * The routine efficiently decomposes n as a sum of powers of
- * two. The desired power is a product of two-to-the-kth
- * powers of x. Thus to compute the 32767 power of x requires
- * 28 multiplications instead of 32767 multiplications.
- *
- *
- *
- * ACCURACY:
- *
- *
- * Relative error:
- * arithmetic x domain n domain # trials peak rms
- * IEEE .001,1000 -1022,1023 50000 4.3e-17 7.8e-18
- * IEEE 1,2 -1022,1023 20000 3.9e-17 7.6e-18
- * IEEE .99,1.01 0,8700 10000 3.6e-16 7.2e-17
- *
- * Returns MAXNUM on overflow, zero on underflow.
- *
- */
-
-/* powil.c */
-
-/*
-Cephes Math Library Release 2.2: December, 1990
-Copyright 1984, 1990 by Stephen L. Moshier
-Direct inquiries to 30 Frost Street, Cambridge, MA 02140
-*/
-
-#include <math.h>
-extern long double MAXNUML, MAXLOGL, MINLOGL;
-extern long double LOGE2L;
-#ifdef ANSIPROT
-extern long double frexpl ( long double, int * );
-#else
-long double frexpl();
-#endif
-
-long double powil( x, nn )
-long double x;
-int nn;
-{
-long double w, y;
-long double s;
-int n, e, sign, asign, lx;
-
-if( x == 0.0L )
- {
- if( nn == 0 )
- return( 1.0L );
- else if( nn < 0 )
- return( MAXNUML );
- else
- return( 0.0L );
- }
-
-if( nn == 0 )
- return( 1.0L );
-
-
-if( x < 0.0L )
- {
- asign = -1;
- x = -x;
- }
-else
- asign = 0;
-
-
-if( nn < 0 )
- {
- sign = -1;
- n = -nn;
- }
-else
- {
- sign = 1;
- n = nn;
- }
-
-/* Overflow detection */
-
-/* Calculate approximate logarithm of answer */
-s = x;
-s = frexpl( s, &lx );
-e = (lx - 1)*n;
-if( (e == 0) || (e > 64) || (e < -64) )
- {
- s = (s - 7.0710678118654752e-1L) / (s + 7.0710678118654752e-1L);
- s = (2.9142135623730950L * s - 0.5L + lx) * nn * LOGE2L;
- }
-else
- {
- s = LOGE2L * e;
- }
-
-if( s > MAXLOGL )
- {
- mtherr( "powil", OVERFLOW );
- y = MAXNUML;
- goto done;
- }
-
-if( s < MINLOGL )
- {
- mtherr( "powil", UNDERFLOW );
- return(0.0L);
- }
-/* Handle tiny denormal answer, but with less accuracy
- * since roundoff error in 1.0/x will be amplified.
- * The precise demarcation should be the gradual underflow threshold.
- */
-if( s < (-MAXLOGL+2.0L) )
- {
- x = 1.0L/x;
- sign = -sign;
- }
-
-/* First bit of the power */
-if( n & 1 )
- y = x;
-
-else
- {
- y = 1.0L;
- asign = 0;
- }
-
-w = x;
-n >>= 1;
-while( n )
- {
- w = w * w; /* arg to the 2-to-the-kth power */
- if( n & 1 ) /* if that bit is set, then include in product */
- y *= w;
- n >>= 1;
- }
-
-
-done:
-
-if( asign )
- y = -y; /* odd power of negative number */
-if( sign < 0 )
- y = 1.0L/y;
-return(y);
-}