show me a rapid 16-bit lookup table style arctan implementation, input arguments is sin and cos
时间: 2023-07-02 15:11:19 浏览: 62
Here is an example implementation of a 16-bit lookup table style arctan function in C, taking sin and cos as input arguments:
```c
#include <stdint.h>
#include <math.h>
#define LOOKUP_TABLE_SIZE 256
// Lookup table for arctan function
static const int16_t atan_table[LOOKUP_TABLE_SIZE] = {
0, 401, 804, 1207, 1611, 2014, 2417, 2821, 3224, 3628, 4032, 4436, 4840, 5244, 5648, 6052,
6456, 6861, 7265, 7669, 8074, 8478, 8883, 9288, 9693, 10098, 10503, 10908, 11314, 11719, 12125, 12531,
12937, 13343, 13749, 14156, 14562, 14969, 15376, 15783, 16190, 16597, 17005, 17412, 17820, 18228, 18636, 19044,
19452, 19861, 20269, 20678, 21086, 21495, 21904, 22313, 22722, 23131, 23540, 23950, 24359, 24769, 25179, 25589,
25999, 26409, 26819, 27230, 27640, 28051, 28462, 28873, 29284, 29695, 30106, 30518, 30929, 31341, 31753, 32165,
32577, 32989, 33401, 33813, 34225, 34638, 35050, 35463, 35876, 36288, 36701, 37114, 37527, 37940, 38353, 38766,
39179, 39592, 40005, 40418, 40831, 41245, 41658, 42072, 42485, 42899, 43312, 43726, 44140, 44554, 44968, 45382,
45796, 46210, 46624, 47039, 47453, 47868, 48283, 48697, 49112, 49527, 49942, 50357, 50772, 51187, 51603, 52018,
52434, 52849, 53265, 53681, 54097, 54513, 54929, 55345, 55762, 56178, 56595, 57011, 57428, 57845, 58262, 58679,
59096, 59513, 59931, 60348, 60766, 61184, 61602, 62020, 62438, 62856, 63274, 63693, 64111, 64530, 64949, 65368,
65787, 66206, 66625, 67044, 67463, 67882, 68302, 68721, 69141, 69560, 69980, 70400, 70820, 71240, 71660, 72081,
72501, 72922, 73342, 73763, 74184, 74605, 75026, 75447, 75868, 76289, 76711, 77132, 77554, 77976, 78397, 78819,
79241, 79663, 80085, 80508, 80930, 81353, 81775, 82198, 82621, 83043, 83466, 83889, 84312, 84735, 85158, 85582,
86005, 86429, 86852, 87276, 87700, 88124, 88548, 88972, 89396, 89820, 90244, 90668, 91093, 91517, 91942, 92366,
92791, 93216, 93641, 94066, 94491, 94916, 95341, 95766, 96192, 96617, 97043, 97468, 97894, 98320, 98746, 99172,
};
int16_t fast_atan2(int16_t sin_val, int16_t cos_val) {
// Calculate the absolute value of sin and cos
uint16_t abs_sin = sin_val >= 0 ? sin_val : -sin_val;
uint16_t abs_cos = cos_val >= 0 ? cos_val : -cos_val;
// Determine the quadrant of the angle
uint16_t angle_quadrant = 0;
if (abs_sin <= abs_cos) {
angle_quadrant = abs_sin * 256 / abs_cos;
} else {
angle_quadrant = abs_cos * 256 / abs_sin;
angle_quadrant = 90 - angle_quadrant;
}
// Look up the arctan value from the table
return sin_val < 0 ? -atan_table[angle_quadrant] : atan_table[angle_quadrant];
}
```
This implementation uses a lookup table with 256 entries to approximate the arctan function. The input sin and cos values are used to determine the quadrant of the angle, and the corresponding arctan value is looked up from the table. Note that this implementation assumes that the input values are 16-bit signed integers.
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