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imath: add sqrti() function

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Benjamin Valentin 2023-03-22 14:08:52 +01:00 committed by Benjamin Valentin
parent 69a6b3cb14
commit eefa1b86b5
1 changed files with 31 additions and 7 deletions
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38
sys/include/imath.h
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@ -27,12 +27,12 @@
extern "C" { extern "C" {
#endif #endif
#define ISIN_PERIOD 0x8000 /**< Period of the isin() function */ #define SINI_PERIOD 0x8000 /**< Period of the fast_sini() function */
#define ISIN_MAX 0x1000 /**< Max value of the isin() function */ #define SINI_MAX 0x1000 /**< Max value of the fast_sini() function */
#define ISIN_MIN -0x1000 /**< Min value of the isin() function */ #define SINI_MIN -0x1000 /**< Min value of the fast_sini() function */
/** /**
* @brief Internal isin/icos helper function * @brief Internal fast_sini/fast_cosi helper function
* @internal * @internal
* *
* @param[in] x Input parameter * @param[in] x Input parameter
@ -66,7 +66,7 @@ int32_t _ihelp(int32_t x)
* @param x angle (with 2^15 units/circle) * @param x angle (with 2^15 units/circle)
* @return sine value (-2^12 ≤ y ≤ 2^12) * @return sine value (-2^12 ≤ y ≤ 2^12)
*/ */
static inline int32_t isin(int32_t x) static inline int32_t fast_sini(int32_t x)
{ {
static const int32_t qN = 13; static const int32_t qN = 13;
@ -83,16 +83,40 @@ static inline int32_t isin(int32_t x)
* @param x angle (with 2^15 units/circle) * @param x angle (with 2^15 units/circle)
* @return sine value (-2^12 ≤ y ≤ 2^12) * @return sine value (-2^12 ≤ y ≤ 2^12)
*/ */
static inline int32_t icos(int32_t x) static inline int32_t fast_cosi(int32_t x)
{ {
static const int32_t qN = 13; static const int32_t qN = 13;
int32_t c = (x + (ISIN_PERIOD >> 2)) << (30 - qN); int32_t c = (x + (SINI_PERIOD >> 2)) << (30 - qN);
int32_t y = _ihelp(x); int32_t y = _ihelp(x);
return c >= 0 ? y :-y; return c >= 0 ? y :-y;
} }
/**
* @brief Square root of an integer
*
* @param x unsigned integer value
* @return square root of @p x
*/
static inline unsigned sqrti(unsigned x)
{
if (x <= 1) {
return x;
}
/* initial estimate */
unsigned y0 = x >> 1;
unsigned y1 = (y0 + x / y0) >> 1;
while (y1 < y0) {
y0 = y1;
y1 = (y0 + x / y0) >> 1;
}
return y0;
}
#ifdef __cplusplus #ifdef __cplusplus
} }
#endif #endif