uClibc now has a math library. muahahahaha!

 -Erik

1 files changed, 203 insertions, 0 deletions

diff --git a/libm/double/exp.c b/libm/double/exp.c
new file mode 100644
index 000000000..6d0a8a872
--- /dev/null
+++ b/libm/double/exp.c
@@ -0,0 +1,203 @@
+/*							exp.c
+ *
+ *	Exponential function
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * double x, y, exp();
+ *
+ * y = exp( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns e (2.71828...) raised to the x power.
+ *
+ * Range reduction is accomplished by separating the argument
+ * into an integer k and fraction f such that
+ *
+ *     x    k  f
+ *    e  = 2  e.
+ *
+ * A Pade' form  1 + 2x P(x**2)/( Q(x**2) - P(x**2) )
+ * of degree 2/3 is used to approximate exp(f) in the basic
+ * interval [-0.5, 0.5].
+ *
+ *
+ * ACCURACY:
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    DEC       +- 88       50000       2.8e-17     7.0e-18
+ *    IEEE      +- 708      40000       2.0e-16     5.6e-17
+ *
+ *
+ * Error amplification in the exponential function can be
+ * a serious matter.  The error propagation involves
+ * exp( X(1+delta) ) = exp(X) ( 1 + X*delta + ... ),
+ * which shows that a 1 lsb error in representing X produces
+ * a relative error of X times 1 lsb in the function.
+ * While the routine gives an accurate result for arguments
+ * that are exactly represented by a double precision
+ * computer number, the result contains amplified roundoff
+ * error for large arguments not exactly represented.
+ *
+ *
+ * ERROR MESSAGES:
+ *
+ *   message         condition      value returned
+ * exp underflow    x < MINLOG         0.0
+ * exp overflow     x > MAXLOG         INFINITY
+ *
+ */
+
+/*
+Cephes Math Library Release 2.8:  June, 2000
+Copyright 1984, 1995, 2000 by Stephen L. Moshier
+*/
+
+
+/*	Exponential function	*/
+
+#include <math.h>
+
+#ifdef UNK
+
+static double P[] = {
+ 1.26177193074810590878E-4,
+ 3.02994407707441961300E-2,
+ 9.99999999999999999910E-1,
+};
+static double Q[] = {
+ 3.00198505138664455042E-6,
+ 2.52448340349684104192E-3,
+ 2.27265548208155028766E-1,
+ 2.00000000000000000009E0,
+};
+static double C1 = 6.93145751953125E-1;
+static double C2 = 1.42860682030941723212E-6;
+#endif
+
+#ifdef DEC
+static unsigned short P[] = {
+0035004,0047156,0127442,0057502,
+0036770,0033210,0063121,0061764,
+0040200,0000000,0000000,0000000,
+};
+static unsigned short Q[] = {
+0033511,0072665,0160662,0176377,
+0036045,0070715,0124105,0132777,
+0037550,0134114,0142077,0001637,
+0040400,0000000,0000000,0000000,
+};
+static unsigned short sc1[] = {0040061,0071000,0000000,0000000};
+#define C1 (*(double *)sc1)
+static unsigned short sc2[] = {0033277,0137216,0075715,0057117};
+#define C2 (*(double *)sc2)
+#endif
+
+#ifdef IBMPC
+static unsigned short P[] = {
+0x4be8,0xd5e4,0x89cd,0x3f20,
+0x2c7e,0x0cca,0x06d1,0x3f9f,
+0x0000,0x0000,0x0000,0x3ff0,
+};
+static unsigned short Q[] = {
+0x5fa0,0xbc36,0x2eb6,0x3ec9,
+0xb6c0,0xb508,0xae39,0x3f64,
+0xe074,0x9887,0x1709,0x3fcd,
+0x0000,0x0000,0x0000,0x4000,
+};
+static unsigned short sc1[] = {0x0000,0x0000,0x2e40,0x3fe6};
+#define C1 (*(double *)sc1)
+static unsigned short sc2[] = {0xabca,0xcf79,0xf7d1,0x3eb7};
+#define C2 (*(double *)sc2)
+#endif
+
+#ifdef MIEEE
+static unsigned short P[] = {
+0x3f20,0x89cd,0xd5e4,0x4be8,
+0x3f9f,0x06d1,0x0cca,0x2c7e,
+0x3ff0,0x0000,0x0000,0x0000,
+};
+static unsigned short Q[] = {
+0x3ec9,0x2eb6,0xbc36,0x5fa0,
+0x3f64,0xae39,0xb508,0xb6c0,
+0x3fcd,0x1709,0x9887,0xe074,
+0x4000,0x0000,0x0000,0x0000,
+};
+static unsigned short sc1[] = {0x3fe6,0x2e40,0x0000,0x0000};
+#define C1 (*(double *)sc1)
+static unsigned short sc2[] = {0x3eb7,0xf7d1,0xcf79,0xabca};
+#define C2 (*(double *)sc2)
+#endif
+
+#ifdef ANSIPROT
+extern double polevl ( double, void *, int );
+extern double p1evl ( double, void *, int );
+extern double floor ( double );
+extern double ldexp ( double, int );
+extern int isnan ( double );
+extern int isfinite ( double );
+#else
+double polevl(), p1evl(), floor(), ldexp();
+int isnan(), isfinite();
+#endif
+extern double LOGE2, LOG2E, MAXLOG, MINLOG, MAXNUM;
+#ifdef INFINITIES
+extern double INFINITY;
+#endif
+
+double exp(x)
+double x;
+{
+double px, xx;
+int n;
+
+#ifdef NANS
+if( isnan(x) )
+	return(x);
+#endif
+if( x > MAXLOG)
+	{
+#ifdef INFINITIES
+	return( INFINITY );
+#else
+	mtherr( "exp", OVERFLOW );
+	return( MAXNUM );
+#endif
+	}
+
+if( x < MINLOG )
+	{
+#ifndef INFINITIES
+	mtherr( "exp", UNDERFLOW );
+#endif
+	return(0.0);
+	}
+
+/* Express e**x = e**g 2**n
+ *   = e**g e**( n loge(2) )
+ *   = e**( g + n loge(2) )
+ */
+px = floor( LOG2E * x + 0.5 ); /* floor() truncates toward -infinity. */
+n = px;
+x -= px * C1;
+x -= px * C2;
+
+/* rational approximation for exponential
+ * of the fractional part:
+ * e**x = 1 + 2x P(x**2)/( Q(x**2) - P(x**2) )
+ */
+xx = x * x;
+px = x * polevl( xx, P, 2 );
+x =  px/( polevl( xx, Q, 3 ) - px );
+x = 1.0 + 2.0 * x;
+
+/* multiply by power of 2 */
+x = ldexp( x, n );
+return(x);
+}