| /* origin: FreeBSD /usr/src/lib/msun/src/s_atanf.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 "libm.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[] = { |
| 3.3333328366e-01, -1.9999158382e-01, 1.4253635705e-01, -1.0648017377e-01, 6.1687607318e-02, |
| }; |
| |
| float atanf(float x) { |
| float_t w, s1, s2, z; |
| uint32_t ix, sign; |
| int id; |
| |
| GET_FLOAT_WORD(ix, x); |
| sign = ix >> 31; |
| ix &= 0x7fffffff; |
| if (ix >= 0x4c800000) { /* if |x| >= 2**26 */ |
| if (isnan(x)) |
| return x; |
| z = atanhi[3] + 0x1p-120f; |
| return sign ? -z : z; |
| } |
| if (ix < 0x3ee00000) { /* |x| < 0.4375 */ |
| if (ix < 0x39800000) { /* |x| < 2**-12 */ |
| if (ix < 0x00800000) /* raise underflow for subnormal x */ |
| FORCE_EVAL(x * x); |
| return x; |
| } |
| id = -1; |
| } else { |
| x = fabsf(x); |
| if (ix < 0x3f980000) { /* |x| < 1.1875 */ |
| if (ix < 0x3f300000) { /* 7/16 <= |x| < 11/16 */ |
| id = 0; |
| x = (2.0f * x - 1.0f) / (2.0f + x); |
| } else { /* 11/16 <= |x| < 19/16 */ |
| id = 1; |
| x = (x - 1.0f) / (x + 1.0f); |
| } |
| } else { |
| if (ix < 0x401c0000) { /* |x| < 2.4375 */ |
| id = 2; |
| x = (x - 1.5f) / (1.0f + 1.5f * x); |
| } else { /* 2.4375 <= |x| < 2**26 */ |
| id = 3; |
| x = -1.0f / 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])); |
| s2 = w * (aT[1] + w * aT[3]); |
| if (id < 0) |
| return x - x * (s1 + s2); |
| z = atanhi[id] - ((x * (s1 + s2) - atanlo[id]) - x); |
| return sign ? -z : z; |
| } |
