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-rw-r--r--libm/float/exp10f.c115
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diff --git a/libm/float/exp10f.c b/libm/float/exp10f.c
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-/* exp10f.c
- *
- * Base 10 exponential function
- * (Common antilogarithm)
- *
- *
- *
- * SYNOPSIS:
- *
- * float x, y, exp10f();
- *
- * y = exp10f( x );
- *
- *
- *
- * DESCRIPTION:
- *
- * Returns 10 raised to the x power.
- *
- * Range reduction is accomplished by expressing the argument
- * as 10**x = 2**n 10**f, with |f| < 0.5 log10(2).
- * A polynomial approximates 10**f.
- *
- *
- *
- * ACCURACY:
- *
- * Relative error:
- * arithmetic domain # trials peak rms
- * IEEE -38,+38 100000 9.8e-8 2.8e-8
- *
- * ERROR MESSAGES:
- *
- * message condition value returned
- * exp10 underflow x < -MAXL10 0.0
- * exp10 overflow x > MAXL10 MAXNUM
- *
- * IEEE single arithmetic: MAXL10 = 38.230809449325611792.
- *
- */
-
-/*
-Cephes Math Library Release 2.2: June, 1992
-Copyright 1984, 1987, 1988, 1992 by Stephen L. Moshier
-Direct inquiries to 30 Frost Street, Cambridge, MA 02140
-*/
-
-
-#include <math.h>
-
-static float P[] = {
- 2.063216740311022E-001,
- 5.420251702225484E-001,
- 1.171292686296281E+000,
- 2.034649854009453E+000,
- 2.650948748208892E+000,
- 2.302585167056758E+000
-};
-
-/*static float LOG102 = 3.01029995663981195214e-1;*/
-static float LOG210 = 3.32192809488736234787e0;
-static float LG102A = 3.00781250000000000000E-1;
-static float LG102B = 2.48745663981195213739E-4;
-static float MAXL10 = 38.230809449325611792;
-
-
-
-
-extern float MAXNUMF;
-
-float floorf(float), ldexpf(float, int), polevlf(float, float *, int);
-
-float exp10f(float xx)
-{
-float x, px, qx;
-short n;
-
-x = xx;
-if( x > MAXL10 )
- {
- mtherr( "exp10f", OVERFLOW );
- return( MAXNUMF );
- }
-
-if( x < -MAXL10 ) /* Would like to use MINLOG but can't */
- {
- mtherr( "exp10f", UNDERFLOW );
- return(0.0);
- }
-
-/* The following is necessary because range reduction blows up: */
-if( x == 0 )
- return(1.0);
-
-/* Express 10**x = 10**g 2**n
- * = 10**g 10**( n log10(2) )
- * = 10**( g + n log10(2) )
- */
-px = x * LOG210;
-qx = floorf( px + 0.5 );
-n = qx;
-x -= qx * LG102A;
-x -= qx * LG102B;
-
-/* rational approximation for exponential
- * of the fractional part:
- * 10**x - 1 = 2x P(x**2)/( Q(x**2) - P(x**2) )
- */
-px = 1.0 + x * polevlf( x, P, 5 );
-
-/* multiply by power of 2 */
-x = ldexpf( px, n );
-
-return(x);
-}