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Commit 81e8b16d authored by Siarhei Vishniakou's avatar Siarhei Vishniakou
Browse files

Use vector instead of VLA in solveLeastSquares 

For simpler tracking of the sizes of the arrays, use vector instead of
VLA. Also, VLA is not part of c++ standard. It's also being removed from
the kernel code.

Bug: 167946721
Test: atest libinput_tests
Change-Id: I03e5ad934bc3d9f451c76d0415c6a1254ec0053a
parent 411b8e6f

libs/input/VelocityTracker.cpp

+22 −17
Original line number Diff line number Diff line
@@ -416,13 +416,15 @@ void LeastSquaresVelocityTrackerStrategy::addMovement( 
 * http://en.wikipedia.org/wiki/Numerical_methods_for_linear_least_squares

 * http://en.wikipedia.org/wiki/Gram-Schmidt

 */

static bool solveLeastSquares(const float* x, const float* y,

        const float* w, uint32_t m, uint32_t n, float* outB, float* outDet) {

static bool solveLeastSquares(const std::vector<float>& x, const std::vector<float>& y,

                              const std::vector<float>& w, uint32_t n, float* outB, float* outDet) {

    const size_t m = x.size();

#if DEBUG_STRATEGY

    ALOGD("solveLeastSquares: m=%d, n=%d, x=%s, y=%s, w=%s", int(m), int(n),

            vectorToString(x, m).c_str(), vectorToString(y, m).c_str(),

            vectorToString(w, m).c_str());

#endif

    LOG_ALWAYS_FATAL_IF(m != y.size() || m != w.size(), "Mismatched vector sizes");



    // Expand the X vector to a matrix A, pre-multiplied by the weights.

    float a[n][m]; // column-major order
@@ -539,7 +541,9 @@ static bool solveLeastSquares(const float* x, const float* y, 
 * the default implementation

 */

static std::optional<std::array<float, 3>> solveUnweightedLeastSquaresDeg2(

        const float* x, const float* y, size_t count) {

        const std::vector<float>& x, const std::vector<float>& y) {

    const size_t count = x.size();

    LOG_ALWAYS_FATAL_IF(count != y.size(), "Mismatching array sizes");

    // Solving y = a*x^2 + b*x + c

    float sxi = 0, sxiyi = 0, syi = 0, sxi2 = 0, sxi3 = 0, sxi2yi = 0, sxi4 = 0;
@@ -591,11 +595,11 @@ bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id, 
    outEstimator->clear();



    // Iterate over movement samples in reverse time order and collect samples.

    float x[HISTORY_SIZE];

    float y[HISTORY_SIZE];

    float w[HISTORY_SIZE];

    float time[HISTORY_SIZE];

    uint32_t m = 0;

    std::vector<float> x;

    std::vector<float> y;

    std::vector<float> w;

    std::vector<float> time;



    uint32_t index = mIndex;

    const Movement& newestMovement = mMovements[mIndex];

    do {
@@ -610,13 +614,14 @@ bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id, 
        }



        const VelocityTracker::Position& position = movement.getPosition(id);

        x[m] = position.x;

        y[m] = position.y;

        w[m] = chooseWeight(index);

        time[m] = -age * 0.000000001f;

        x.push_back(position.x);

        y.push_back(position.y);

        w.push_back(chooseWeight(index));

        time.push_back(-age * 0.000000001f);

        index = (index == 0 ? HISTORY_SIZE : index) - 1;

    } while (++m < HISTORY_SIZE);

    } while (x.size() < HISTORY_SIZE);



    const size_t m = x.size();

    if (m == 0) {

        return false; // no data

    }
@@ -629,8 +634,8 @@ bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id, 


    if (degree == 2 && mWeighting == WEIGHTING_NONE) {

        // Optimize unweighted, quadratic polynomial fit

        std::optional<std::array<float, 3>> xCoeff = solveUnweightedLeastSquaresDeg2(time, x, m);

        std::optional<std::array<float, 3>> yCoeff = solveUnweightedLeastSquaresDeg2(time, y, m);

        std::optional<std::array<float, 3>> xCoeff = solveUnweightedLeastSquaresDeg2(time, x);

        std::optional<std::array<float, 3>> yCoeff = solveUnweightedLeastSquaresDeg2(time, y);

        if (xCoeff && yCoeff) {

            outEstimator->time = newestMovement.eventTime;

            outEstimator->degree = 2;
@@ -645,8 +650,8 @@ bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id, 
        // General case for an Nth degree polynomial fit

        float xdet, ydet;

        uint32_t n = degree + 1;

        if (solveLeastSquares(time, x, w, m, n, outEstimator->xCoeff, &xdet)

                && solveLeastSquares(time, y, w, m, n, outEstimator->yCoeff, &ydet)) {

        if (solveLeastSquares(time, x, w, n, outEstimator->xCoeff, &xdet) &&

            solveLeastSquares(time, y, w, n, outEstimator->yCoeff, &ydet)) {

            outEstimator->time = newestMovement.eventTime;

            outEstimator->degree = degree;

            outEstimator->confidence = xdet * ydet;