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simplify atan initial angle expression

This commit is contained in:
Matt Huszagh 2020-12-17 08:02:54 -08:00
parent 2ddaab8fae
commit d9d500743f
1 changed files with 6 additions and 12 deletions
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18
dsp/src/trig.rs
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@ -50,19 +50,13 @@ pub fn atan2(y: i32, x: i32) -> i32 {
let ratio = (min << 15) / max; let ratio = (min << 15) / max;
let mut angle = { let mut angle = {
// pi/4, referenced to i16::MAX const K1: i32 =
const PI_4_FACTOR: i32 = 25735; ((1_f64 / 4_f64 + 0.285_f64 / PI) * (1 << 16) as f64) as i32;
// 0.285, referenced to i16::MAX const K2: i32 = ((0.285_f64 / PI) * (1 << 16) as f64) as i32;
const FACTOR_0285: i32 = 9339;
// 1/pi, referenced to u16::MAX
const PI_INVERTED_FACTOR: i32 = 20861;
let r1 = shift_round(ratio * PI_4_FACTOR, 15); let ratio_squared = shift_round(ratio * ratio, 15);
let r2 = shift_round(
(shift_round(ratio * FACTOR_0285, 15)) * (i16::MAX as i32 - ratio), ratio * K1 - K2 * ratio_squared
15,
);
(r1 + r2) * PI_INVERTED_FACTOR
}; };
if uy > ux { if uy > ux {