interpolation.cpp

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/**
 * @file    interpolation.cpp
 * @brief   Linear interpolation algorithms
 *
 * See test_interpolation_3d.cpp
 *
 *
 * @date Oct 17, 2013
 * @author Andrey Belomutskiy, (c) 2012-2020
 * @author Dmitry Sidin, (c) 2015
 */
 
#include "pch.h"
 
#include "efi_interpolation.h"
 
/** @brief  Linear interpolation by two points
 *
 * @param   x1 key of the first point
 * @param   y1 value of the first point
 * @param   x2 key of the second point
 * @param   y2 value of the second point
 * @param   X key to be interpolated
 *
 * @note    For example, "interpolateMsg("", engineConfiguration.tpsMin, 0, engineConfiguration.tpsMax, 100, adc);"
 * @see interpolateClamped
 */
float interpolateMsg(const char *msg, float x1, float y1, float x2, float y2, float x) {
    if (std::isnan(x1) || std::isnan(x2) || std::isnan(y1) || std::isnan(y2)) {
        warning(ObdCode::CUSTOM_ERR_INTERPOLATE_1, "interpolate%s: why param", msg);
        return NAN;
    }
    if (std::isnan(x)) {
        warning(ObdCode::CUSTOM_ERR_INTERPOLATE_2, "interpolate%s: why X", msg);
        return NAN;
    }
    // todo: double comparison using EPS
    if (x1 == x2) {
        /**
         * we could end up here for example while resetting bins while changing engine type
         */
        warning(ObdCode::CUSTOM_ERR_INTERPOLATE_3, "interpolate%s: Same x1 and x2 in interpolate: %.2f/%.2f", msg, x1, x2);
        return NAN;
    }
 
    // a*x1 + b = y1
    // a*x2 + b = y2
//  efiAssertVoid(ObdCode::CUSTOM_ERR_ASSERT_VOID, x1 != x2, "no way we can interpolate");
    float a = INTERPOLATION_A(x1, y1, x2, y2);
    if (std::isnan(a)) {
        warning(ObdCode::CUSTOM_ERR_INTERPOLATE_4, "interpolate%s: why a", msg);
        return NAN;
    }
    float b = y1 - a * x1;
    return a * x + b;
}
 
float interpolateClampedWithValidation(float x1, float y1, float x2, float y2, float x) {
    if (x1 >= x2) {
        criticalError("interpolateClamped %f has to be smaller than %f", x1, x2);
    }
    return interpolateClamped(x1, y1, x2, y2, x);
}
 
/**
 * todo: use 'interpolateClampedWithValidation' wider?
 * @see interpolateMsg
 */
float interpolateClamped(float x1, float y1, float x2, float y2, float x) {
    // note how we assume order of x1 and x2 here! see also interpolateClampedWithValidation
    if (x <= x1)
        return y1;
    if (x >= x2)
        return y2;
 
    // todo: do we care with code duplication with interpolateMsg above?
    float a = INTERPOLATION_A(x1, y1, x2, y2);
    float b = y1 - a * x1;
    return a * x + b;
}