Search rework (#61)

Elo   | 250.57 +- 44.99 (95%)
SPRT  | 60.0+0.60s Threads=1 Hash=64MB
LLR   | 1.05 (-2.94, 2.94) [0.50, 2.50]
Games | N: 340 W: 252 L: 42 D: 46
Penta | [3, 4, 33, 40, 90]

Bench: 3746694

.clang-format

@@ -2,3 +2,4 @@
 Language: Cpp
 BasedOnStyle: Google
 ColumnLimit: 100
+IndentWidth: 4

CMakeLists.txt

@@ -70,7 +70,7 @@
 cmake_minimum_required(VERSION 3.16)
 set(CMAKE_CXX_STANDARD 20)
 project(Zagreus)
-set(ZAGREUS_VERSION_MAJOR "3")
+set(ZAGREUS_VERSION_MAJOR "4")
 set(ZAGREUS_VERSION_MINOR "0")
 
 # Default values

README.md

@@ -18,18 +18,29 @@ You can download binaries here: https://github.com/Dannyj1/Zagreus/releases
 This engine requires a GUI that supports the UCI (Universal Chess Interface) protocol to use it. I personally
 use [CuteChess](https://cutechess.com/).
 
+# Development
+
+Development of all new changes and bug fixes happens in a separate branch for each change. When the change is properly
+tested using OpenBench and proven to improve ELO, it will be merged with the master branch. Because of this, the master
+branch is not the latest released version and may contain bugs.
+Every stable release (as in the version has been uploaded under releases) will have a tag. If you want to compile the
+stable version for yourself, you can use the tag. You can list all tags and search for tags under the branches dropdown
+on GitHub.
+
 # Features
 - Bitboard board representation with Plain Magic Bitboards for sliding piece move generation
-- Tapered Evaluation consisting of material balance, mobility, very simple connectivity, king safety, piece square
-  tables and more
-- Evaluation values automatically tuned with a gradient descent tuner with the Adam optimizer.
+- Tapered Evaluation with:
+  - Material
+  - Piece-Square Tables
+  - Several evaluation terms per piece type (e.g. passed pawn, king safety, etc.)
+  - Penalty for undefended minor pieces
+  - And more
+- Evaluation values automatically tuned using a gradient descent tuner with the Adam optimizer.
 - Principal Variation Search with Alpha-Beta pruning
-- Aspiration Windows
 - Quiescence Search with delta pruning and SEE move ordering
 - Move ordering using MVV/LVA, killer moves, history heuristic, countermove heuristic
 - Transposition Table
 - Null Move Pruning
-- Late Move Reduction
 - And more! This list is constantly growing and changing, but it is difficult to keep track of all features and changes.
 
 # UCI Options
@@ -42,7 +53,8 @@ Zagreus Engine has the following UCI options that can be changed:
 # Build Instructions
 
 To build Zagreus, you will need to use LLVM. On Windows, I use [LLVM MinGW](https://github.com/mstorsjo/llvm-mingw). On
-Linux I just use [LLVM](https://releases.llvm.org/download.html).
+Linux I just use [LLVM](https://releases.llvm.org/download.html), but it is also possible to use GCC. LLVM seems to have
+slightly better performance.
 Zagreus uses CMake to build. On Windows you can use the [CMake-GUI](https://cmake.org/runningcmake/). On Linux, use the
 following commands:
 
@@ -51,10 +63,11 @@ Clone the repository:
 git clone https://github.com/Dannyj1/Zagreus.git
 ```
 
-Set the compiler to clang++:
+If you want to use Clang/LLVM, set the compiler to clang++ (not required. If you don't run these commands, your default
+compiler will be used which works fine in most cases):
 ```bash
-export CC=/usr/bin/clang-15
-export CXX=/usr/bin/clang++-15
+export CC=/usr/bin/clang-<version here>
+export CXX=/usr/bin/clang++-<version here>
 ```
 Build:
 ```bash

senjo/BackgroundCommand.cpp

@@ -215,7 +215,7 @@ namespace senjo {
                     continue;
                 }
 
-                int depth = toNumber<int>(depthToken.substr(1));
+                int16_t depth = toNumber<int>(depthToken.substr(1));
                 if (depth < 1) {
                     Output() << "--- invalid depth: " << depthToken;
                     break;
@@ -252,7 +252,7 @@ namespace senjo {
 //! \param[out] leaf_count The actual leaf count at \p depth
 //! \return false if leaf_count count does not match expected leaf count
 //-----------------------------------------------------------------------------
-    bool PerftCommandHandle::process(const int depth,
+    bool PerftCommandHandle::process(const int16_t depth,
                                      const uint64_t expected_leaf_count,
                                      uint64_t &leaf_count) {
         if ((maxDepth > 0) && (depth > maxDepth)) {

senjo/BackgroundCommand.h

@@ -157,7 +157,7 @@ namespace senjo {
         void doWork();
 
     private:
-        bool process(const int depth, const uint64_t expected_leaf_count,
+        bool process(const int16_t depth, const uint64_t expected_leaf_count,
                      uint64_t &leaf_count);
 
         static const std::string _TEST_FILE;

senjo/ChessEngine.h

@@ -241,7 +241,7 @@ namespace senjo {
         //! \param[in] depth How many half-moves (plies) to search
         //! \return The number of leaf nodes visited at \p depth
         //---------------------------------------------------------------------------
-        virtual uint64_t perft(const int depth) = 0;
+        virtual uint64_t perft(const int16_t depth) = 0;
 
         //---------------------------------------------------------------------------
         //! \brief Execute search on current position to find best move

senjo/GoParams.h

@@ -30,7 +30,7 @@ namespace senjo {
     struct GoParams {
         bool infinite = false; // SearchManager until the "stop" command
         bool ponder = false; // Start searching in pondering mode
-        int depth = 0; // Maximum number of half-moves (plies) to search
+        int16_t depth = 0; // Maximum number of half-moves (plies) to search
         int movestogo = 0; // Number of moves remaining until next time control
         uint64_t binc = 0; // BLACK increment per move in milliseconds
         uint64_t btime = 0; // Milliseconds remaining on black's clock

senjo/SearchStats.h

@@ -29,7 +29,7 @@ namespace senjo {
 
 //-----------------------------------------------------------------------------
     struct SearchStats {
-        int depth = 0; // The current search depth
+        int16_t depth = 0; // The current search depth
         int seldepth = 0; // The maximum selective depth reached on "move"
         uint64_t nodes = 0; // The number of nodes searched so far
         uint64_t qnodes = 0; // The number of quiescence nodes searched so far