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authorRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
committerRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
commit0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 (patch)
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initial check-in, version 0.5.0v0.5.0
Diffstat (limited to 'src/math/k_tanf.c')
-rw-r--r--src/math/k_tanf.c105
1 files changed, 105 insertions, 0 deletions
diff --git a/src/math/k_tanf.c b/src/math/k_tanf.c
new file mode 100644
index 00000000..99ede58c
--- /dev/null
+++ b/src/math/k_tanf.c
@@ -0,0 +1,105 @@
+/* k_tanf.c -- float version of k_tan.c
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+static const float
+one = 1.0000000000e+00, /* 0x3f800000 */
+pio4 = 7.8539812565e-01, /* 0x3f490fda */
+pio4lo= 3.7748947079e-08, /* 0x33222168 */
+T[] = {
+ 3.3333334327e-01, /* 0x3eaaaaab */
+ 1.3333334029e-01, /* 0x3e088889 */
+ 5.3968254477e-02, /* 0x3d5d0dd1 */
+ 2.1869488060e-02, /* 0x3cb327a4 */
+ 8.8632395491e-03, /* 0x3c11371f */
+ 3.5920790397e-03, /* 0x3b6b6916 */
+ 1.4562094584e-03, /* 0x3abede48 */
+ 5.8804126456e-04, /* 0x3a1a26c8 */
+ 2.4646313977e-04, /* 0x398137b9 */
+ 7.8179444245e-05, /* 0x38a3f445 */
+ 7.1407252108e-05, /* 0x3895c07a */
+ -1.8558637748e-05, /* 0xb79bae5f */
+ 2.5907305826e-05, /* 0x37d95384 */
+};
+
+float
+__kernel_tanf(float x, float y, int iy)
+{
+ float z,r,v,w,s;
+ int32_t ix,hx;
+ GET_FLOAT_WORD(hx,x);
+ ix = hx&0x7fffffff; /* high word of |x| */
+ if(ix<0x31800000) { /* x < 2**-28 */
+ if ((int) x == 0) { /* generate inexact */
+ if ((ix | (iy + 1)) == 0)
+ return one / fabsf(x);
+ else {
+ if (iy == 1)
+ return x;
+ else { /* compute -1 / (x+y) carefully */
+ double a, t;
+
+ z = w = x + y;
+ GET_FLOAT_WORD(ix, z);
+ SET_FLOAT_WORD(z, ix & 0xfffff000);
+ v = y - (z - x);
+ t = a = -one / w;
+ GET_FLOAT_WORD(ix, t);
+ SET_FLOAT_WORD(t, ix & 0xfffff000);
+ s = one + t * z;
+ return t + a * (s + t * v);
+ }
+ }
+ }
+ }
+ if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
+ if(hx<0) {x = -x; y = -y;}
+ z = pio4-x;
+ w = pio4lo-y;
+ x = z+w; y = 0.0;
+ }
+ z = x*x;
+ w = z*z;
+ /* Break x^5*(T[1]+x^2*T[2]+...) into
+ * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
+ * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
+ */
+ r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
+ v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
+ s = z*x;
+ r = y + z*(s*(r+v)+y);
+ r += T[0]*s;
+ w = x+r;
+ if(ix>=0x3f2ca140) {
+ v = (float)iy;
+ return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
+ }
+ if(iy==1) return w;
+ else { /* if allow error up to 2 ulp,
+ simply return -1.0/(x+r) here */
+ /* compute -1.0/(x+r) accurately */
+ float a,t;
+ int32_t i;
+ z = w;
+ GET_FLOAT_WORD(i,z);
+ SET_FLOAT_WORD(z,i&0xfffff000);
+ v = r-(z - x); /* z+v = r+x */
+ t = a = -(float)1.0/w; /* a = -1.0/w */
+ GET_FLOAT_WORD(i,t);
+ SET_FLOAT_WORD(t,i&0xfffff000);
+ s = (float)1.0+t*z;
+ return t+a*(s+t*v);
+ }
+}