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Code Issues Wiki Activity

optimize math (#5287)

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* optimize math

Results in considerable flash saving

* log_approx, exp_approx, pow_approx

Taken from https://github.com/jhjourdan/SIMD-math-prims/blob/master/simd_math_prims.h

* Fix pow in rangefinder

* Use approximate function in baro calculation

Maximum error is < 20cm

* fixup! Fix pow in rangefinder
This commit is contained in:
Petr Ledvina 2018-03-03 13:26:33 +01:00 • committed by Michael Keller
parent b64802d931
commit c11d016bc7
7 changed files with 117 additions and 7 deletions
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4
src/main/sensors/barometer.c
View file

@ -332,7 +332,7 @@ int32_t baroCalculateAltitude(void)
// calculates height from ground via baro readings
// see: https://github.com/diydrones/ardupilot/blob/master/libraries/AP_Baro/AP_Baro.cpp#L140
if (isBaroCalibrationComplete()) {
BaroAlt_tmp = lrintf((1.0f - powf((float)(baroPressureSum / PRESSURE_SAMPLE_COUNT) / 101325.0f, 0.190295f)) * 4433000.0f); // in cm
BaroAlt_tmp = lrintf((1.0f - pow_approx((float)(baroPressureSum / PRESSURE_SAMPLE_COUNT) / 101325.0f, 0.190295f)) * 4433000.0f); // in cm
BaroAlt_tmp -= baroGroundAltitude;
baro.BaroAlt = lrintf((float)baro.BaroAlt * CONVERT_PARAMETER_TO_FLOAT(barometerConfig()->baro_noise_lpf) + (float)BaroAlt_tmp * (1.0f - CONVERT_PARAMETER_TO_FLOAT(barometerConfig()->baro_noise_lpf))); // additional LPF to reduce baro noise
}
@ -348,7 +348,7 @@ void performBaroCalibrationCycle(void)
baroGroundPressure -= baroGroundPressure / 8;
baroGroundPressure += baroPressureSum / PRESSURE_SAMPLE_COUNT;
baroGroundAltitude = (1.0f - powf((baroGroundPressure / 8) / 101325.0f, 0.190295f)) * 4433000.0f;
baroGroundAltitude = (1.0f - pow_approx((baroGroundPressure / 8) / 101325.0f, 0.190295f)) * 4433000.0f;
if (baroGroundPressure == savedGroundPressure)
calibratingB = 0;

3
src/main/sensors/rangefinder.c
View file

@ -233,7 +233,8 @@ static int16_t computePseudoSnr(int32_t newReading) {
static bool snrReady = false;
int16_t pseudoSnr = 0;
snrSamples[snrSampleIndex] = constrain((int)(pow(newReading - previousReading, 2) / 10), 0, 6400);
const int delta = newReading - previousReading;
snrSamples[snrSampleIndex] = constrain(delta * delta / 10, 0, 6400);
++snrSampleIndex;
if (snrSampleIndex == SNR_SAMPLES) {
snrSampleIndex = 0;