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authorAndreas Jaeger <aj@suse.de>2001-06-19 07:24:40 +0000
committerAndreas Jaeger <aj@suse.de>2001-06-19 07:24:40 +0000
commitba0fd1ba028fb241260e80b4d1f669944eae29e0 (patch)
treef7881231b3a6935d23e73bac2d9c0578de022d6e /sysdeps/ieee754/ldbl-128
parent86dbe05e18341c5e2e9c15855230570b330b84c4 (diff)
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128 bit implementation of tanh.
Diffstat (limited to 'sysdeps/ieee754/ldbl-128')
-rw-r--r--sysdeps/ieee754/ldbl-128/s_tanhl.c106
1 files changed, 106 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_tanhl.c b/sysdeps/ieee754/ldbl-128/s_tanhl.c
new file mode 100644
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+++ b/sysdeps/ieee754/ldbl-128/s_tanhl.c
@@ -0,0 +1,106 @@
+/* s_tanhl.c -- long double version of s_tanh.c.
+ * Conversion to long double by Ulrich Drepper,
+ * Cygnus Support, drepper@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+/* Changes for 128-bit long double contributed by
+ Stephen L. Moshier <moshier@na-net.ornl.gov> */
+
+/* tanhl(x)
+ * Return the Hyperbolic Tangent of x
+ *
+ * Method :
+ * x -x
+ * e - e
+ * 0. tanhl(x) is defined to be -----------
+ * x -x
+ * e + e
+ * 1. reduce x to non-negative by tanhl(-x) = -tanhl(x).
+ * 2. 0 <= x <= 2**-57 : tanhl(x) := x*(one+x)
+ * -t
+ * 2**-57 < x <= 1 : tanhl(x) := -----; t = expm1l(-2x)
+ * t + 2
+ * 2
+ * 1 <= x <= 40.0 : tanhl(x) := 1- ----- ; t=expm1l(2x)
+ * t + 2
+ * 40.0 < x <= INF : tanhl(x) := 1.
+ *
+ * Special cases:
+ * tanhl(NaN) is NaN;
+ * only tanhl(0)=0 is exact for finite argument.
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+static const long double one = 1.0, two = 2.0, tiny = 1.0e-4900L;
+#else
+static long double one = 1.0, two = 2.0, tiny = 1.0e-4900L;
+#endif
+
+#ifdef __STDC__
+long double
+__tanhl (long double x)
+#else
+long double
+__tanhl (x)
+ long double x;
+#endif
+{
+ long double t, z;
+ u_int32_t jx, ix;
+ ieee854_long_double_shape_type u;
+
+ /* Words of |x|. */
+ u.value = x;
+ jx = u.parts32.w0;
+ ix = jx & 0x7fffffff;
+ /* x is INF or NaN */
+ if (ix >= 0x7fff0000)
+ {
+ /* for NaN it's not important which branch: tanhl(NaN) = NaN */
+ if (jx & 0x80000000)
+ return one / x - one; /* tanhl(-inf)= -1; */
+ else
+ return one / x + one; /* tanhl(+inf)=+1 */
+ }
+
+ /* |x| < 40 */
+ if (ix < 0x40044000)
+ {
+ if (u.value == 0)
+ return x; /* x == +- 0 */
+ if (ix < 0x3fc60000) /* |x| < 2^-57 */
+ return x * (one + tiny); /* tanh(small) = small */
+ u.parts32.w0 = ix; /* Absolute value of x. */
+ if (ix >= 0x3fff0000)
+ { /* |x| >= 1 */
+ t = __expm1l (two * u.value);
+ z = one - two / (t + two);
+ }
+ else
+ {
+ t = __expm1l (-two * u.value);
+ z = -t / (t + two);
+ }
+ /* |x| > 40, return +-1 */
+ }
+ else
+ {
+ z = one - tiny; /* raised inexact flag */
+ }
+ return (jx & 0x80000000) ? -z : z;
+}
+weak_alias (__tanhl, tanhl)