From d3f14efbbdb7fc07f74b39bee00f58749f0391e8 Mon Sep 17 00:00:00 2001
From: Ari Vuollet <ari.vuollet@kapsi.fi>
Date: Sun, 21 May 2023 20:22:56 +0300
Subject: [PATCH] _adaptive sleep

---
 Source/Engine/Engine/Engine.cpp               | 41 ++++++++++++++++---
 .../Engine/Platform/Win32/Win32Platform.cpp   |  9 ++++
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/Source/Engine/Engine/Engine.cpp b/Source/Engine/Engine/Engine.cpp
index 20063ca0f..f50be408b 100644
--- a/Source/Engine/Engine/Engine.cpp
+++ b/Source/Engine/Engine/Engine.cpp
@@ -165,16 +165,41 @@ int32 Engine::Main(const Char* cmdLine)
     while (!ShouldExit())
     {
         // Reduce CPU usage by introducing idle time if the engine is running very fast and has enough time to spend
-        if ((useSleep && Time::UpdateFPS > ZeroTolerance) || !Platform::GetHasFocus())
+        if ((useSleep && Time::UpdateFPS > ZeroTolerance && Time::PhysicsFPS > ZeroTolerance && Time::DrawFPS > ZeroTolerance))
         {
             double nextTick = Time::GetNextTick();
             double timeToTick = nextTick - Platform::GetTimeSeconds();
 
-            // Sleep less than needed, some platforms may sleep slightly more than requested
-            if (timeToTick > 0.002)
+            if (timeToTick > 0)
             {
-                PROFILE_CPU_NAMED("Idle");
-                Platform::Sleep(1);
+                // Sleep less than needed, some platforms may sleep slightly more than requested
+                static double adaptiveMinSleep = 0.00001;
+                if (timeToTick > adaptiveMinSleep)
+                {
+                    PROFILE_CPU_NAMED("Idle");
+                    while (timeToTick > adaptiveMinSleep)
+                    {
+                        Platform::Sleep(1);
+                        //Platform::Sleep(-1111);
+                        timeToTick = nextTick - Platform::GetTimeSeconds();
+                    }
+                }
+
+                if (timeToTick < 0)
+                {
+                    adaptiveMinSleep += -timeToTick * 0.15;
+                    //Log::Logger::Write(LogType::Info, TEXT("{0}, adaptive: {1}"), -timeToTick * 1000.0, adaptiveMinSleep);
+                }
+                else
+                {
+                    adaptiveMinSleep -= 0.000000001;
+                    PROFILE_CPU_NAMED("IdleBusyLoop");
+                    while (timeToTick > 0)
+                    {
+                        Platform::Sleep(-1111);
+                        timeToTick = nextTick - Platform::GetTimeSeconds();
+                    }
+                }
             }
         }
 
@@ -218,6 +243,12 @@ int32 Engine::Main(const Char* cmdLine)
             Time::OnEndDraw();
             FrameMark;
         }
+
+        /*{
+            PROFILE_CPU_NAMED("CollectResults");
+            // Collect physics simulation results (does nothing if Simulate hasn't been called in the previous loop step)
+            Physics::CollectResults();
+        }*/
     }
 
     // Call on exit event
diff --git a/Source/Engine/Platform/Win32/Win32Platform.cpp b/Source/Engine/Platform/Win32/Win32Platform.cpp
index d46706621..0dbf71cab 100644
--- a/Source/Engine/Platform/Win32/Win32Platform.cpp
+++ b/Source/Engine/Platform/Win32/Win32Platform.cpp
@@ -370,6 +370,15 @@ void Win32Platform::SetThreadAffinityMask(uint64 affinityMask)
 
 void Win32Platform::Sleep(int32 milliseconds)
 {
+    if (milliseconds < 0)
+    {
+        ::SwitchToThread();
+        return;
+    }
+
+    //::Sleep(milliseconds);
+    //return;
+
     static thread_local HANDLE timer = NULL;
     if (timer == NULL)
     {