rooty/LibrePilot
1
0
Fork 0
mirror of https://bitbucket.org/librepilot/librepilot.git synced 2025-01-18 03:52:11 +01:00
Code Issues Releases Activity

OP-1535 - uses union in fast_invsqrt

Browse Source
This commit is contained in:
Alessio Morale 2014-10-14 05:31:40 +02:00
parent 5d074063d1
commit fe20e39d5c
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
flight/libraries/math/mathmisc.h
View File

@ -124,17 +124,20 @@ static inline float y_on_curve(float x, const pointf points[], int num_points)
static inline float fast_invsqrtf(float number)
{
uint32_t i;
float x2, y;
const float threehalfs = 1.5F;
union {
float f;
uint32_t u;
} i;
x2 = number * 0.5F;
y = number;
void *tmp = &y;
i = *(uint32_t *)tmp; // evil floating point bit level hacking
i = 0x5f3759df - (i >> 1); // what the fxck?
tmp = &i;
y = *(float *)tmp;
i.f = y; // evil floating point bit level hacking
i.u = 0x5f3759df - (i.u >> 1); // what the fxck?
y = i.f;
y = y * (threehalfs - (x2 * y * y)); // 1st iteration
// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed