52ms -> 46ms. Render the board in parallel to generating the next one.

Author: Jumbub

makefile

@@ -1,7 +1,7 @@
 CC = g++
 
-COMPILER_FLAGS = -Wall -std=c++2a
-COMPILER_FLAGS_BENCHMARK = $(COMPILER_FLAGS) -isystem benchmark/include -Lbenchmark/build/src -lbenchmark -lpthread
+COMPILER_FLAGS = -Wall -std=c++2a -lpthread
+COMPILER_FLAGS_BENCHMARK = $(COMPILER_FLAGS) -isystem benchmark/include -Lbenchmark/build/src -lbenchmark
 COMPILER_FLAGS_PROFILE = $(COMPILER_FLAGS) -pg
 COMPILER_FLAGS_DEBUG = $(COMPILER_FLAGS) -ggdb
 

results/benchmark.txt

@@ -1,5 +1,5 @@
-----------------------------------------------------------------------------
-Benchmark                                  Time             CPU   Iterations
-----------------------------------------------------------------------------
-BM_NextBoard/min_time:5.000             50.4 ms         50.4 ms          125
-BM_RenderNextBoard/min_time:5.000       55.8 ms         55.8 ms          111
+------------------------------------------------------------------------
+Benchmark                              Time             CPU   Iterations
+------------------------------------------------------------------------
+BM_NextBoard/min_time:5.000         50.0 ms         49.9 ms          126
+BM_RenderBoard/min_time:5.000       6.96 ms         6.95 ms         1006

src/entrypoints/benchmark.cpp

@@ -17,7 +17,7 @@ static void BM_NextBoard(benchmark::State &state) {
   free(get<0>(board));
 }
 
-static void BM_RenderNextBoard(benchmark::State &state) {
+static void BM_RenderBoard(benchmark::State &state) {
   auto board = benchmarkBoard(TEST_WIDTH, TEST_HEIGHT);
 
   // Initialize graphics
@@ -29,7 +29,6 @@ static void BM_RenderNextBoard(benchmark::State &state) {
                                     SDL_TEXTUREACCESS_STATIC, TEST_WIDTH, TEST_HEIGHT);
 
   for (auto _ : state) {
-    board = nextBoard(board);
     renderBoardSdl(board, renderer, texture);
   }
 
@@ -43,6 +42,6 @@ static void BM_RenderNextBoard(benchmark::State &state) {
 }
 
 BENCHMARK(BM_NextBoard)->Unit(benchmark::kMillisecond)->MinTime(5);
-BENCHMARK(BM_RenderNextBoard)->Unit(benchmark::kMillisecond)->MinTime(5);
+BENCHMARK(BM_RenderBoard)->Unit(benchmark::kMillisecond)->MinTime(5);
 
 BENCHMARK_MAIN();

src/entrypoints/interactive.cpp

@@ -5,6 +5,13 @@
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_timer.h>
 #include <iostream>
+#include <thread>
+#include <thread>
+#include <future>
+
+void nextBoardThreaded(Board board, std::promise<Board> promise) {
+  promise.set_value(nextBoard(board));
+}
 
 int main() {
   // Initialize SDL
@@ -24,12 +31,17 @@ int main() {
                                    SDL_TEXTUREACCESS_STATIC, width, height);
 
   // Generate initial board
-  auto p1 = startProfiling();
   auto board = boardForSdlWindow(window);
-  stopProfiling(p1, "Generated first board");
 
   bool running = true;
+  bool recreateBoard = false;
   while (running) {
+    auto loopTimer = startProfiling();
+
+    std::promise<Board> nextBoardPromise;
+    auto nextBoardFuture = nextBoardPromise.get_future();
+    std::thread nextBoardThread(nextBoardThreaded, board, std::move(nextBoardPromise));
+
     while (SDL_PollEvent(&event)) {
       // Exit when told, or Escape is pressed
       if ((event.type == SDL_KEYDOWN && event.key.keysym.sym == SDLK_ESCAPE) ||
@@ -40,24 +52,28 @@ int main() {
       // Re-create board when Enter is pressed
       else if (event.type == SDL_KEYDOWN &&
                event.key.keysym.scancode == SDL_SCANCODE_RETURN) {
-
-        free(get<0>(board));
-        board = boardForSdlWindow(window);
-        int width, height;
-        SDL_GetWindowSize(window, &width, &height);
-        SDL_DestroyTexture(texture);
-        texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
-                                    SDL_TEXTUREACCESS_STATIC, width, height);
+        recreateBoard = true;
       }
     }
 
-    auto p2 = startProfiling();
-    board = nextBoard(board);
-    stopProfiling(p2, "Calculated next board");
-
-    auto p3 = startProfiling();
     renderBoardSdl(board, renderer, texture);
-    stopProfiling(p3, "Rendered next board");
+
+    nextBoardThread.join();
+    board = nextBoardFuture.get();
+
+    // Re-create board when computation is complete
+    if (recreateBoard) {
+      free(get<0>(board));
+      board = boardForSdlWindow(window);
+      int width, height;
+      SDL_GetWindowSize(window, &width, &height);
+      SDL_DestroyTexture(texture);
+      texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
+                                  SDL_TEXTUREACCESS_STATIC, width, height);
+      recreateBoard = false;
+    }
+
+    stopProfiling(loopTimer, "Done loop");
   }
 
   free(get<0>(board));