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-rw-r--r--modules/fdlibm/src/k_tanf.cpp65
1 files changed, 65 insertions, 0 deletions
diff --git a/modules/fdlibm/src/k_tanf.cpp b/modules/fdlibm/src/k_tanf.cpp
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+++ b/modules/fdlibm/src/k_tanf.cpp
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+/* k_tanf.c -- float version of k_tan.c
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Optimized by Bruce D. Evans.
+ */
+
+/*
+ * ====================================================
+ * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#ifndef INLINE_KERNEL_TANDF
+//#include <sys/cdefs.h>
+//__FBSDID("$FreeBSD$");
+#endif
+
+#include "math_private.h"
+
+/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */
+static const double
+T[] = {
+ 0x15554d3418c99f.0p-54, /* 0.333331395030791399758 */
+ 0x1112fd38999f72.0p-55, /* 0.133392002712976742718 */
+ 0x1b54c91d865afe.0p-57, /* 0.0533812378445670393523 */
+ 0x191df3908c33ce.0p-58, /* 0.0245283181166547278873 */
+ 0x185dadfcecf44e.0p-61, /* 0.00297435743359967304927 */
+ 0x1362b9bf971bcd.0p-59, /* 0.00946564784943673166728 */
+};
+
+#ifdef INLINE_KERNEL_TANDF
+static __inline
+#endif
+float
+__kernel_tandf(double x, int iy)
+{
+ double z,r,w,s,t,u;
+
+ z = x*x;
+ /*
+ * Split up the polynomial into small independent terms to give
+ * opportunities for parallel evaluation. The chosen splitting is
+ * micro-optimized for Athlons (XP, X64). It costs 2 multiplications
+ * relative to Horner's method on sequential machines.
+ *
+ * We add the small terms from lowest degree up for efficiency on
+ * non-sequential machines (the lowest degree terms tend to be ready
+ * earlier). Apart from this, we don't care about order of
+ * operations, and don't need to care since we have precision to
+ * spare. However, the chosen splitting is good for accuracy too,
+ * and would give results as accurate as Horner's method if the
+ * small terms were added from highest degree down.
+ */
+ r = T[4]+z*T[5];
+ t = T[2]+z*T[3];
+ w = z*z;
+ s = z*x;
+ u = T[0]+z*T[1];
+ r = (x+s*u)+(s*w)*(t+w*r);
+ if(iy==1) return r;
+ else return -1.0/r;
+}