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Remove Quake Fast Inverse SQRT (it isn't faster)

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This commit is contained in:
Scott Lahteine
2018-07-04 18:41:41 -05:00
parent e7e896e7d7
commit 68e6650df7
3 changed files with 1 additions and 54 deletions
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23
Marlin/src/module/delta.cpp
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@ -90,31 +90,8 @@ void recalc_delta_settings() {
*
* - Disable the home_offset (M206) and/or position_shift (G92)
* features to remove up to 12 float additions.
*
* - Use a fast-inverse-sqrt function and add the reciprocal.
* (see above)
*/
#if ENABLED(DELTA_FAST_SQRT) && defined(__AVR__)
/**
* Fast inverse sqrt from Quake III Arena
* See: https://en.wikipedia.org/wiki/Fast_inverse_square_root
*/
float Q_rsqrt(float number) {
long i;
float x2, y;
const float threehalfs = 1.5f;
x2 = number * 0.5f;
y = number;
i = * ( long * ) &y; // evil floating point bit level hacking
i = 0x5F3759DF - ( i >> 1 ); // what the f***?
y = * ( float * ) &i;
y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration
// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
return y;
}
#endif
#define DELTA_DEBUG(VAR) do { \
SERIAL_ECHOPAIR("cartesian X:", VAR[X_AXIS]); \
SERIAL_ECHOPAIR(" Y:", VAR[Y_AXIS]); \

13
Marlin/src/module/delta.h
View File

@ -64,19 +64,8 @@ void recalc_delta_settings();
* (see above)
*/
#if ENABLED(DELTA_FAST_SQRT) && defined(__AVR__)
/**
* Fast inverse sqrt from Quake III Arena
* See: https://en.wikipedia.org/wiki/Fast_inverse_square_root
*/
float Q_rsqrt(float number);
#define _SQRT(n) (1.0f / Q_rsqrt(n))
#else
#define _SQRT(n) SQRT(n)
#endif
// Macro to obtain the Z position of an individual tower
#define DELTA_Z(V,T) V[Z_AXIS] + _SQRT( \
#define DELTA_Z(V,T) V[Z_AXIS] + SQRT( \
delta_diagonal_rod_2_tower[T] - HYPOT2( \
delta_tower[T][X_AXIS] - V[X_AXIS], \
delta_tower[T][Y_AXIS] - V[Y_AXIS] \