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-rw-r--r--src/math/s_atanf.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/src/math/s_atanf.c b/src/math/s_atanf.c
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+/* s_atanf.c -- float version of s_atan.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@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.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const float atanhi[] = {
+ 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
+ 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
+ 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
+ 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
+};
+
+static const float atanlo[] = {
+ 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
+ 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
+ 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
+ 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
+};
+
+static const float aT[] = {
+ 3.3333334327e-01, /* 0x3eaaaaaa */
+ -2.0000000298e-01, /* 0xbe4ccccd */
+ 1.4285714924e-01, /* 0x3e124925 */
+ -1.1111110449e-01, /* 0xbde38e38 */
+ 9.0908870101e-02, /* 0x3dba2e6e */
+ -7.6918758452e-02, /* 0xbd9d8795 */
+ 6.6610731184e-02, /* 0x3d886b35 */
+ -5.8335702866e-02, /* 0xbd6ef16b */
+ 4.9768779427e-02, /* 0x3d4bda59 */
+ -3.6531571299e-02, /* 0xbd15a221 */
+ 1.6285819933e-02, /* 0x3c8569d7 */
+};
+
+ static const float
+one = 1.0,
+huge = 1.0e30;
+
+float
+atanf(float x)
+{
+ float w,s1,s2,z;
+ int32_t ix,hx,id;
+
+ GET_FLOAT_WORD(hx,x);
+ ix = hx&0x7fffffff;
+ if(ix>=0x50800000) { /* if |x| >= 2^34 */
+ if(ix>0x7f800000)
+ return x+x; /* NaN */
+ if(hx>0) return atanhi[3]+atanlo[3];
+ else return -atanhi[3]-atanlo[3];
+ } if (ix < 0x3ee00000) { /* |x| < 0.4375 */
+ if (ix < 0x31000000) { /* |x| < 2^-29 */
+ if(huge+x>one) return x; /* raise inexact */
+ }
+ id = -1;
+ } else {
+ x = fabsf(x);
+ if (ix < 0x3f980000) { /* |x| < 1.1875 */
+ if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
+ id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
+ } else { /* 11/16<=|x|< 19/16 */
+ id = 1; x = (x-one)/(x+one);
+ }
+ } else {
+ if (ix < 0x401c0000) { /* |x| < 2.4375 */
+ id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
+ } else { /* 2.4375 <= |x| < 2^66 */
+ id = 3; x = -(float)1.0/x;
+ }
+ }}
+ /* end of argument reduction */
+ z = x*x;
+ w = z*z;
+ /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
+ s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
+ s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
+ if (id<0) return x - x*(s1+s2);
+ else {
+ z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
+ return (hx<0)? -z:z;
+ }
+}