source:
asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/math/round.c
Last change on this file was 352, checked in by , 6 years ago | |
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File size: 597 bytes |
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1 | #include "libm.h" |
2 | |
3 | #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1 |
4 | #define EPS DBL_EPSILON |
5 | #elif FLT_EVAL_METHOD==2 |
6 | #define EPS LDBL_EPSILON |
7 | #endif |
8 | static const double_t toint = 1/EPS; |
9 | |
10 | double round(double x) |
11 | { |
12 | union {double f; uint64_t i;} u = {x}; |
13 | int e = u.i >> 52 & 0x7ff; |
14 | double_t y; |
15 | |
16 | if (e >= 0x3ff+52) |
17 | return x; |
18 | if (u.i >> 63) |
19 | x = -x; |
20 | if (e < 0x3ff-1) { |
21 | /* raise inexact if x!=0 */ |
22 | FORCE_EVAL(x + toint); |
23 | return 0*u.f; |
24 | } |
25 | y = x + toint - toint - x; |
26 | if (y > 0.5) |
27 | y = y + x - 1; |
28 | else if (y <= -0.5) |
29 | y = y + x + 1; |
30 | else |
31 | y = y + x; |
32 | if (u.i >> 63) |
33 | y = -y; |
34 | return y; |
35 | } |
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