From 590a4473ff37ea30c07a4af6b5a84dba569df742 Mon Sep 17 00:00:00 2001
From: AnasImloul <pydev27@gmail.com>
Date: Tue, 31 Oct 2023 22:20:35 +0100
Subject: [PATCH] Added multithreading optimization

---
 grid.cpp | 10 ++++++--
 main.cpp |  6 ++---
 move.cpp | 76 +++++++++++++++++++++++++++++++++++++-------------------
 move.h   |  2 +-
 4 files changed, 63 insertions(+), 31 deletions(-)

diff --git a/grid.cpp b/grid.cpp
index 4be8a18..b95ff04 100644
--- a/grid.cpp
+++ b/grid.cpp
@@ -55,10 +55,16 @@ void grid::show() {
             long long value = (tiles[i * SIZE + j] != 0 ? (1 << tiles[i * SIZE + j]) : 0);
             std::cout << value << std::string(maxLength1 - length(value), ' ') << " ";
         }
-        for (int i = 0; i < 1 + maxLength1 / 3; i++)
+        if (i + 1 == SIZE) {
             std::cout << std::endl;
+        } else {
+            for (int i = 0; i < 1 + maxLength1 / 3; i++)
+                std::cout << std::endl;
+        }
     }
-    std::cout << std::endl;
+    std::cout << "Score: " << score << std::endl;
+
+
 }
 
 bool grid::up() {
diff --git a/main.cpp b/main.cpp
index b2893eb..4244bc7 100644
--- a/main.cpp
+++ b/main.cpp
@@ -12,17 +12,17 @@ void fastIO() {
 }
 
 int main() {
-    std::srand(std::time(nullptr));
+    // std::srand(std::time(nullptr));
     fastIO();
 
     grid g;
 
     int move;
     do {
-        move = move::bestMove(g, 8);
+        move = move::bestMove(g, 12);
         g.move(move);
         g.show();
-        std::cout << "Score: " << g.getScore() << std::endl;
+        std::cout << std::endl;
     } while (move != -1);
 
 }
diff --git a/move.cpp b/move.cpp
index 9f7c1c4..e94b435 100644
--- a/move.cpp
+++ b/move.cpp
@@ -1,47 +1,73 @@
-//
-// Created by user on 29/10/2023.
-//
-
 #include "move.h"
 #include <iostream>
+#include <thread>
+#include <vector>
+#include <atomic>
 
 #define max(a, b) ((a) > (b) ? (a) : (b))
 
 namespace move {
     int bestMove(grid& g, int depth) {
-        int64_t bestScore = 0;
-        int bestDir = -1, calls = 0;
-        bestMoveHelper(g, depth, bestScore, bestDir, -1, calls);
-        std::cout << "calls: " << calls << std::endl;
+        std::vector<std::thread> threads;
+        int64_t scores[16];
+        for (int i = 0; i < 16; i++) scores[i] = -1;
+
+        for (int first : DIRECTIONS) {
+            for (int second : DIRECTIONS) {
+                threads.emplace_back([&](int dir) {
+                    grid g1(g);
+                    if (g1.move(dir / 4)) {
+                        grid g2(g1);
+                        if (g2.move(dir % 4)) {
+                            int64_t score = -1;
+                            bestScore(g2, depth - 2, score);
+                            scores[dir] = score;
+                        } else {
+                            int64_t score = evaluate(g1) >> depth;
+                            scores[dir] = score;
+                        }
+                    }
+                }, first * 4 + second);
+            }
+        }
+
+        for (auto& thread : threads) {
+            thread.join();
+        }
+
+        int bestDir = -1;
+        int64_t _bestScore = -1;
+
+        for (int i = 0; i < 16; i++) {
+            int64_t score = scores[i];
+
+            if (score > _bestScore) {
+                _bestScore = score;
+                bestDir = i / 4;
+            }
+        }
+
         return bestDir;
+
     }
 
     inline int64_t evaluate(grid& g) { return (g.getEmpty() << 16) + g.getScore(); }
 
     namespace {
-        int bestMoveHelper(const grid& g, int depth, int &bestScore, int &bestDir, int move) {
-            if (depth == 0 || g.isBlocked()) {
-                return evaluate(g);
-            }
+        void bestScore(grid& g, int depth, int64_t& currentBestScore) {
 
-            if (move == -1) {
-                // if the move is -1, we are at the root of the tree
-                // we will have dynamic depth based on the number of empty tiles
-                // the less empty tiles, the more depth
-                depth = max(depth * (SIZE - g.getEmpty() / SIZE) / SIZE, 4);
-            }
+            int64_t score = evaluate(g) >> depth;
+            currentBestScore = max(currentBestScore, score);
+
+            if (depth == 0)
+                return;
 
             for (int dir : DIRECTIONS) {
                 grid g1(g);
-                g1.move(dir);
-                int score = bestMoveHelper(g1, depth - 1, bestScore, bestDir, (move == -1 ? dir : move));
-                if (score > bestScore) {
-                    bestScore = score;
-                    bestDir = move;
+                if (g1.move(dir)) {
+                    bestScore(g1, depth - 1, currentBestScore);
                 }
             }
-
-            return bestScore;
         }
     }
 
diff --git a/move.h b/move.h
index d80fedd..154530f 100644
--- a/move.h
+++ b/move.h
@@ -13,7 +13,7 @@ namespace move {
     inline int64_t evaluate(grid &g);
 
     namespace {
-        void bestMoveHelper(grid& g, int depth, int64_t &bestScore, int &bestDir, int move, int& calls);
+        void bestScore(grid& g, int depth, int64_t& currentBestScore);
     }
 
 }
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