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https://github.com/k4zmu2a/SpaceCadetPinball.git
synced 2023-12-30 21:52:56 +00:00
Added hybrid sleep/spin wait mode.
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@ -99,6 +99,7 @@ void options::init()
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Options.UncappedUpdatesPerSecond = get_int("Uncapped Updates Per Second", false);
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Options.SoundChannels = get_int("Sound Channels", DefSoundChannels);
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Options.SoundChannels = std::min(MaxSoundChannels, std::max(MinSoundChannels, Options.SoundChannels));
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Options.HybridSleep = get_int("HybridSleep", false);
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winmain::UpdateFrameRate();
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@ -130,6 +131,7 @@ void options::uninit()
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set_int("ShowMenu", Options.ShowMenu);
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set_int("Uncapped Updates Per Second", Options.UncappedUpdatesPerSecond);
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set_int("Sound Channels", Options.SoundChannels);
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set_int("HybridSleep", Options.HybridSleep);
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}
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@ -73,6 +73,7 @@ struct optionsStruct
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bool ShowMenu;
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bool UncappedUpdatesPerSecond;
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int SoundChannels;
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bool HybridSleep;
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};
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struct ControlRef
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@ -42,6 +42,8 @@ std::string winmain::FpsDetails;
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double winmain::UpdateToFrameRatio;
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winmain::DurationMs winmain::TargetFrameTime;
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optionsStruct& winmain::Options = options::Options;
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winmain::DurationMs winmain::SpinThreshold = DurationMs(0.005);
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WelfordState winmain::SleepState{};
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int winmain::WinMain(LPCSTR lpCmdLine)
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{
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@ -115,7 +117,8 @@ int winmain::WinMain(LPCSTR lpCmdLine)
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// If HW fails, fallback to SW SDL renderer.
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SDL_Renderer* renderer = nullptr;
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for (int i = 0; i < 2 && !renderer; i++)
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auto swOffset = strstr(lpCmdLine, "-sw") != nullptr ? 1 : 0;
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for (int i = swOffset; i < 2 && !renderer; i++)
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{
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Renderer = renderer = SDL_CreateRenderer
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(
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@ -288,6 +291,9 @@ int winmain::WinMain(LPCSTR lpCmdLine)
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TimePoint frameEnd;
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if (targetTimeDelta > DurationMs::zero() && !Options.UncappedUpdatesPerSecond)
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{
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if (Options.HybridSleep)
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HybridSleep(targetTimeDelta);
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else
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std::this_thread::sleep_for(targetTimeDelta);
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frameEnd = Clock::now();
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}
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@ -519,6 +525,12 @@ void winmain::RenderUi()
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{
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Options.UncappedUpdatesPerSecond ^= true;
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}
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if (ImGui::MenuItem("Precise Sleep", nullptr, Options.HybridSleep))
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{
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Options.HybridSleep ^= true;
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SleepState = WelfordState{};
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SpinThreshold = DurationMs::zero();
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}
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if (changed)
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{
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@ -947,7 +959,9 @@ void winmain::RenderFrameTimeDialog()
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auto target = static_cast<float>(TargetFrameTime.count());
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auto scale = 1 / (64 / 2 / target);
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ImGui::Text("Target frame time:%03.04fms, 1px:%03.04fms", target, scale);
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auto spin = Options.HybridSleep ? static_cast<float>(SpinThreshold.count()) : 0;
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ImGui::Text("Target frame time:%03.04fms, 1px:%03.04fms, SpinThreshold:%03.04fms",
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target, scale, spin);
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gfr_display->BlitToTexture();
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auto region = ImGui::GetContentRegionAvail();
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ImGui::Image(gfr_display->Texture, region);
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@ -955,3 +969,28 @@ void winmain::RenderFrameTimeDialog()
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ImGui::End();
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ImGui::PopStyleVar();
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}
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void winmain::HybridSleep(DurationMs sleepTarget)
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{
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static constexpr double StdDevFactor = 0.5;
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// This nice concept is from https://blat-blatnik.github.io/computerBear/making-accurate-sleep-function/
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// Sacrifices some CPU time for smaller frame time jitter
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while (sleepTarget > SpinThreshold)
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{
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auto start = Clock::now();
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std::this_thread::sleep_for(DurationMs(1));
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auto end = Clock::now();
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auto actualDuration = DurationMs(end - start);
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sleepTarget -= actualDuration;
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// Update expected sleep duration using Welford's online algorithm
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// With bad timer, this will run away to 100% spin
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SleepState.Advance(actualDuration.count());
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SpinThreshold = DurationMs(SleepState.mean + SleepState.GetStdDev() * StdDevFactor);
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}
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// spin lock
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for (auto start = Clock::now(); DurationMs(Clock::now() - start) < sleepTarget;);
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}
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@ -33,6 +33,31 @@ struct SdlPerformanceClock
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}
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};
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struct WelfordState
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{
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double mean;
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double M2;
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int64_t count;
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WelfordState() : mean(0.005), M2(0), count(1)
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{
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}
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void Advance(double newValue)
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{
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++count;
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auto delta = newValue - mean;
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mean += delta / count;
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M2 += delta * (newValue - mean); //M2n = M2n-1 + (Xn - AvgXn-1) * (Xn - AvgXn)
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}
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double GetStdDev() const
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{
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return std::sqrt(M2 / (count - 1)); // Sn^2 = M2n / (n - 1)
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}
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};
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class winmain
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{
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using Clock = SdlPerformanceClock; // Or std::chrono::steady_clock.
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@ -75,7 +100,10 @@ private:
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static double UpdateToFrameRatio;
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static DurationMs TargetFrameTime;
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static struct optionsStruct& Options;
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static DurationMs SpinThreshold;
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static WelfordState SleepState;
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static void RenderUi();
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static void RenderFrameTimeDialog();
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static void HybridSleep(DurationMs seconds);
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};
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