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gambatte_qt/framework: slightly faster frametime estimation convergence

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utilize intermediate measurements to accumulate a least squares solution.
This commit is contained in:
sinamas 2013-11-24 06:28:22 +01:00
parent ec3ecc9283
commit f82184ef33
2 changed files with 19 additions and 16 deletions
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32
gambatte_qt/src/framework/src/blitterwidget.cpp
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@ -27,30 +27,34 @@ static long limit(long const est, long const ref) {
return std::max(std::min(est, ref + maxdiff), ref - maxdiff);
}
enum { ft_shift = 6 };
FtEst::FtEst(long const frameTime)
: frameTime_(frameTime)
, ft_(4500000 << ft_shift)
, ftAvg_(frameTime << ftavg_shift)
, last_(0)
, count_((ft_ + (frameTime >> 1)) / (frameTime ? frameTime : 1))
, t_(2250000)
, c_(t_ / (frameTime ? frameTime : 1))
, tc_(t_ * c_)
, c2_(c_ * c_)
{
}
void FtEst::update(usec_t const t) {
if (t - last_ < usec_t(ftAvg_ + (ftAvg_ >> 4)) >> ftavg_shift) {
ft_ += t - last_ < usec_t(ftAvg_ - (ftAvg_ >> 4)) >> ftavg_shift
? (ftAvg_ - (ftAvg_ >> 7)) << (ft_shift - ftavg_shift)
: (t - last_) << ft_shift;
count_ += 1 << ft_shift;
t_ += t - last_ < usec_t(ftAvg_ - (ftAvg_ >> 4)) >> ftavg_shift
? ftAvg_ * (0.9921875 / ftavg_scale)
: t - last_;
c_ += 1;
tc_ += t_ * c_;
c2_ += c_ * c_;
long const ftAvgNew = long(float(ft_) * ftavg_scale / count_ + 0.5f);
ftAvg_ = limit((ftAvg_ * 31 + ftAvgNew + 16) >> 5, frameTime_ << ftavg_shift);
if (ft_ > 6000000 << ft_shift) {
ft_ = (ft_ * 3 + 2) >> 2;
count_ = (count_ * 3 + 2) >> 2;
long const ftAvgNew = long(tc_ * ftavg_scale / c2_ + 0.5);
ftAvg_ = limit((ftAvg_ * 31 + ftAvgNew + 16) >> 5,
frameTime_ << ftavg_shift);
if (t_ > 3000000) {
t_ *= 3.0 / 4;
c_ *= 3.0 / 4;
tc_ *= 9.0 / 16;
c2_ *= 9.0 / 16;
}
}

3
gambatte_qt/src/framework/src/blitterwidget.h
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@ -38,10 +38,9 @@ private:
enum { ftavg_scale = 1 << ftavg_shift };
long frameTime_;
long ft_;
long ftAvg_;
usec_t last_;
unsigned count_;
double t_, c_, tc_, c2_;
};
class BlitterWidget : public QWidget {