From 41d99890c1e57d724ace40e09f281267c2613886 Mon Sep 17 00:00:00 2001
From: catbot <catbot@bot.local>
Date: Tue, 16 Jun 2026 15:25:22 +0000
Subject: [PATCH] perf(window): ring buffer for CRAFTER_TIMING frame times
 (#44)

Replace the std::vector<nanoseconds> frameTimes plus
erase(begin()) with a fixed-size std::array ring buffer (head +
count). The previous code memmoved ~99 elements left every frame once
the window filled. LogTiming computes order-independent sum/avg/min/max,
so the ring's write order is irrelevant to the reported stats.

Behind CRAFTER_TIMING only; shipping builds are unaffected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 implementations/Crafter.Graphics-Window.cpp | 34 +++++++++++----------
 interfaces/Crafter.Graphics-Window.cppm     |  9 +++++-
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/implementations/Crafter.Graphics-Window.cpp b/implementations/Crafter.Graphics-Window.cpp
index 1388a03..411ffb1 100644
--- a/implementations/Crafter.Graphics-Window.cpp
+++ b/implementations/Crafter.Graphics-Window.cpp
@@ -657,11 +657,12 @@ void Window::Update() {
 	#ifdef CRAFTER_TIMING
 	frameEnd = std::chrono::high_resolution_clock::now();
 	
-	frameTimes.push_back(totalUpdate+totalRender);
-	
-	// Keep only the last 100 frame times
-	if (frameTimes.size() > 100) {
-		frameTimes.erase(frameTimes.begin());
+	// Ring buffer: overwrite the oldest entry once full. Order doesn't matter
+	// to LogTiming, so we never need to shift elements.
+	frameTimes[frameTimesHead] = totalUpdate+totalRender;
+	frameTimesHead = (frameTimesHead + 1) % frameTimeCapacity;
+	if (frameTimesCount < frameTimeCapacity) {
+		++frameTimesCount;
 	}
 	#endif
 	lastFrameBegin = startTime;
@@ -843,21 +844,22 @@ void Window::LogTiming() {
     std::cout << std::format("Total: {}", duration_cast<std::chrono::milliseconds>(totalUpdate+totalRender)) << std::endl;
     std::cout << std::format("Vblank: {}", duration_cast<std::chrono::milliseconds>(vblank)) << std::endl;
     
-    // Add 100-frame average and min-max timing info
-    if (!frameTimes.empty()) {
+    // Add 100-frame average and min-max timing info. Only the first
+    // frameTimesCount entries of the ring buffer hold valid samples.
+    if (frameTimesCount != 0) {
         // Calculate average
         std::chrono::nanoseconds sum(0);
-        for (const auto& frameTime : frameTimes) {
-            sum += frameTime;
+        for (std::size_t i = 0; i < frameTimesCount; ++i) {
+            sum += frameTimes[i];
         }
-        auto average = sum / frameTimes.size();
-        
+        auto average = sum / frameTimesCount;
+
         // Find min and max
-        auto min = frameTimes.front();
-        auto max = frameTimes.front();
-        for (const auto& frameTime : frameTimes) {
-            if (frameTime < min) min = frameTime;
-            if (frameTime > max) max = frameTime;
+        auto min = frameTimes[0];
+        auto max = frameTimes[0];
+        for (std::size_t i = 0; i < frameTimesCount; ++i) {
+            if (frameTimes[i] < min) min = frameTimes[i];
+            if (frameTimes[i] > max) max = frameTimes[i];
         }
         
         std::cout << std::format("Last 100 Frame Times - Avg: {}, Min: {}, Max: {}", 
diff --git a/interfaces/Crafter.Graphics-Window.cppm b/interfaces/Crafter.Graphics-Window.cppm
index b957882..9068267 100644
--- a/interfaces/Crafter.Graphics-Window.cppm
+++ b/interfaces/Crafter.Graphics-Window.cppm
@@ -164,7 +164,14 @@ export namespace Crafter {
         std::chrono::nanoseconds vblank;
         std::chrono::nanoseconds totalFrame;
         std::chrono::time_point<std::chrono::high_resolution_clock> frameEnd;
-        std::vector<std::chrono::nanoseconds> frameTimes;
+        // Fixed-size ring buffer of the most recent frame times. LogTiming does
+        // order-independent sum/avg/min/max, so head position is irrelevant to
+        // the reported stats; this avoids the per-frame memmove a vector::erase
+        // at the front would incur once full.
+        static constexpr std::size_t frameTimeCapacity = 100;
+        std::array<std::chrono::nanoseconds, frameTimeCapacity> frameTimes{};
+        std::size_t frameTimesHead = 0;
+        std::size_t frameTimesCount = 0;
         void LogTiming();
         #endif