From 1077fa4d772832f77a677ce7fb7c2d513b959e3f Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 10 May 2001 00:40:28 +0000
Subject: uClibc now has a math library.  muahahahaha!  -Erik

---
 libm/double/spence.c | 205 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 205 insertions(+)
 create mode 100644 libm/double/spence.c

(limited to 'libm/double/spence.c')

diff --git a/libm/double/spence.c b/libm/double/spence.c
new file mode 100644
index 000000000..e2a56176b
--- /dev/null
+++ b/libm/double/spence.c
@@ -0,0 +1,205 @@
+/*							spence.c
+ *
+ *	Dilogarithm
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * double x, y, spence();
+ *
+ * y = spence( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Computes the integral
+ *
+ *                    x
+ *                    -
+ *                   | | log t
+ * spence(x)  =  -   |   ----- dt
+ *                 | |   t - 1
+ *                  -
+ *                  1
+ *
+ * for x >= 0.  A rational approximation gives the integral in
+ * the interval (0.5, 1.5).  Transformation formulas for 1/x
+ * and 1-x are employed outside the basic expansion range.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    IEEE      0,4         30000       3.9e-15     5.4e-16
+ *    DEC       0,4          3000       2.5e-16     4.5e-17
+ *
+ *
+ */
+
+/*							spence.c */
+
+
+/*
+Cephes Math Library Release 2.8:  June, 2000
+Copyright 1985, 1987, 1989, 2000 by Stephen L. Moshier
+*/
+
+#include <math.h>
+
+#ifdef UNK
+static double A[8] = {
+  4.65128586073990045278E-5,
+  7.31589045238094711071E-3,
+  1.33847639578309018650E-1,
+  8.79691311754530315341E-1,
+  2.71149851196553469920E0,
+  4.25697156008121755724E0,
+  3.29771340985225106936E0,
+  1.00000000000000000126E0,
+};
+static double B[8] = {
+  6.90990488912553276999E-4,
+  2.54043763932544379113E-2,
+  2.82974860602568089943E-1,
+  1.41172597751831069617E0,
+  3.63800533345137075418E0,
+  5.03278880143316990390E0,
+  3.54771340985225096217E0,
+  9.99999999999999998740E-1,
+};
+#endif
+#ifdef DEC
+static unsigned short A[32] = {
+0034503,0013315,0034120,0157771,
+0036357,0135043,0016766,0150637,
+0037411,0007533,0005212,0161475,
+0040141,0031563,0023217,0120331,
+0040455,0104461,0007002,0155522,
+0040610,0034434,0065721,0120465,
+0040523,0006674,0105671,0054427,
+0040200,0000000,0000000,0000000,
+};
+static unsigned short B[32] = {
+0035465,0021626,0032367,0144157,
+0036720,0016326,0134431,0000406,
+0037620,0161024,0133701,0120766,
+0040264,0131557,0152055,0064512,
+0040550,0152424,0051166,0034272,
+0040641,0006233,0014672,0111572,
+0040543,0006674,0105671,0054425,
+0040200,0000000,0000000,0000000,
+};
+#endif
+#ifdef IBMPC
+static unsigned short A[32] = {
+0x1bff,0xa70a,0x62d9,0x3f08,
+0xda34,0x63be,0xf744,0x3f7d,
+0x5c68,0x6151,0x21eb,0x3fc1,
+0xf41b,0x64d1,0x266e,0x3fec,
+0x5b6a,0x21c0,0xb126,0x4005,
+0x3427,0x8d7a,0x0723,0x4011,
+0x2b23,0x9177,0x61b7,0x400a,
+0x0000,0x0000,0x0000,0x3ff0,
+};
+static unsigned short B[32] = {
+0xf90e,0xc69e,0xa472,0x3f46,
+0x2021,0xd723,0x039a,0x3f9a,
+0x343f,0x96f8,0x1c42,0x3fd2,
+0xad29,0xfa85,0x966d,0x3ff6,
+0xc717,0x8a4e,0x1aa2,0x400d,
+0x526f,0x6337,0x2193,0x4014,
+0x2b23,0x9177,0x61b7,0x400c,
+0x0000,0x0000,0x0000,0x3ff0,
+};
+#endif
+#ifdef MIEEE
+static unsigned short A[32] = {
+0x3f08,0x62d9,0xa70a,0x1bff,
+0x3f7d,0xf744,0x63be,0xda34,
+0x3fc1,0x21eb,0x6151,0x5c68,
+0x3fec,0x266e,0x64d1,0xf41b,
+0x4005,0xb126,0x21c0,0x5b6a,
+0x4011,0x0723,0x8d7a,0x3427,
+0x400a,0x61b7,0x9177,0x2b23,
+0x3ff0,0x0000,0x0000,0x0000,
+};
+static unsigned short B[32] = {
+0x3f46,0xa472,0xc69e,0xf90e,
+0x3f9a,0x039a,0xd723,0x2021,
+0x3fd2,0x1c42,0x96f8,0x343f,
+0x3ff6,0x966d,0xfa85,0xad29,
+0x400d,0x1aa2,0x8a4e,0xc717,
+0x4014,0x2193,0x6337,0x526f,
+0x400c,0x61b7,0x9177,0x2b23,
+0x3ff0,0x0000,0x0000,0x0000,
+};
+#endif
+
+#ifdef ANSIPROT
+extern double fabs ( double );
+extern double log ( double );
+extern double polevl ( double, void *, int );
+#else
+double fabs(), log(), polevl();
+#endif
+extern double PI, MACHEP;
+
+double spence(x)
+double x;
+{
+double w, y, z;
+int flag;
+
+if( x < 0.0 )
+	{
+	mtherr( "spence", DOMAIN );
+	return(0.0);
+	}
+
+if( x == 1.0 )
+	return( 0.0 );
+
+if( x == 0.0 )
+	return( PI*PI/6.0 );
+
+flag = 0;
+
+if( x > 2.0 )
+	{
+	x = 1.0/x;
+	flag |= 2;
+	}
+
+if( x > 1.5 )
+	{
+	w = (1.0/x) - 1.0;
+	flag |= 2;
+	}
+
+else if( x < 0.5 )
+	{
+	w = -x;
+	flag |= 1;
+	}
+
+else
+	w = x - 1.0;
+
+
+y = -w * polevl( w, A, 7) / polevl( w, B, 7 );
+
+if( flag & 1 )
+	y = (PI * PI)/6.0  - log(x) * log(1.0-x) - y;
+
+if( flag & 2 )
+	{
+	z = log(x);
+	y = -0.5 * z * z  -  y;
+	}
+
+return( y );
+}
-- 
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