Last change
on this file since 389 was 389, checked in by coas-nagasima, 5 years ago |
ビルドが通るよう更新
|
-
Property svn:eol-style
set to
native
-
Property svn:mime-type
set to
text/x-csrc;charset=UTF-8
|
File size:
477 bytes
|
Rev | Line | |
---|
[388] | 1 | #include "libm.h"
|
---|
| 2 |
|
---|
| 3 | /* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */
|
---|
| 4 | static const int k = 235;
|
---|
| 5 | static const float kln2 = 0x1.45c778p+7f;
|
---|
| 6 |
|
---|
| 7 | /* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */
|
---|
| 8 | float __expo2f(float x)
|
---|
| 9 | {
|
---|
| 10 | float scale;
|
---|
| 11 |
|
---|
| 12 | /* note that k is odd and scale*scale overflows */
|
---|
| 13 | SET_FLOAT_WORD(scale, (uint32_t)(0x7f + k/2) << 23);
|
---|
| 14 | /* exp(x - k ln2) * 2**(k-1) */
|
---|
| 15 | return expf(x - kln2) * scale * scale;
|
---|
| 16 | }
|
---|
Note:
See
TracBrowser
for help on using the repository browser.