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Refactor times inverse of sqrt 2 calculation (#21293)

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フィルターペーパー 2023-07-07 22:50:21 +08:00 committed by GitHub
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1 changed files with 10 additions and 5 deletions
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quantum/mousekey.c
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@ -25,11 +25,16 @@
#include "mousekey.h" #include "mousekey.h"
static inline int8_t times_inv_sqrt2(int8_t x) { static inline int8_t times_inv_sqrt2(int8_t x) {
// 181/256 is pretty close to 1/sqrt(2) // 181/256 (0.70703125) is used as an approximation for 1/sqrt(2)
// 0.70703125 0.707106781 // because it is close to the exact value which is 0.707106781
// 1 too small for x=99 and x=198 const int16_t n = x * 181;
// This ends up being a mult and discard lower 8 bits const uint16_t d = 256;
return (x * 181) >> 8;
// To ensure that the integer result is rounded accurately after
// division, check the sign of the numerator:
// If negative, subtract half of the denominator before dividing
// Otherwise, add half of the denominator before dividing
return n < 0 ? (n - d / 2) / d : (n + d / 2) / d;
} }
static report_mouse_t mouse_report = {0}; static report_mouse_t mouse_report = {0};