Amalgamate most outstanding strength patches.

To make it easier to make the tournament deadline. * Bad bishop eval (kz04px#56). * Late move pruning changes (kz04px#78). * Improving variable (kz04px#83). * Include promotions in qsearch (kz04px#97). Also include kz04px#95 to make this exactly 4096 bytes, and put in tournament settings (hash/threads) that keep the size below target. vs master (432c06a): ELO | 18.58 +- 9.34 (95%) SPRT | 8.0+0.08s Threads=1 Hash=64MB LLR | 2.97 (-2.94, 2.94) [0.00, 5.00] GAMES | N: 3032 W: 945 L: 783 D: 1304
gcp · Dec 23, 2022 · 6969225 · 6969225
1 parent 432c06a
commit 6969225
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Showing 3 changed files with 37 additions and 14 deletions.
diff --git a/README.md b/README.md
@@ -28,7 +28,7 @@ sh build-mini.sh
 
 ## 4ku-mini Size
 ```
-3,989 bytes
+4,096 bytes
 ```
 
 ---

diff --git a/minifier/minify.py b/minifier/minify.py
@@ -423,6 +423,8 @@ def rename(tokens):
         "pawn_attacked":"dw",
         "no_move":"dx",
         "reduction":"dy",
+        "quiet_moves_evaluated":"dz",
+        "improving":"ea",
         # Labels
         "do_search":"bk",
         "full_window":"bl",

diff --git a/src/main.cpp b/src/main.cpp
@@ -1,13 +1,15 @@
+// clang-format off
+#include <random>
+#include <iostream>
+#include <thread>
 #include <array>
+#include <string>
+#include <cstring>
 #include <cstdint>
 #include <cstdio>
-#include <cstring>
 #include <ctime>
-#include <iostream>
-#include <random>
-#include <string>
-#include <thread>
 #include <vector>
+// clang-format on
 // minify delete on
 #include <sstream>
 // minify delete off
@@ -61,6 +63,7 @@ struct [[nodiscard]] Stack {
     Move moves[218];
     Move move;
     Move killer;
+    int score;
 };
 
 struct [[nodiscard]] TT_Entry {
@@ -87,6 +90,9 @@ const auto keys = []() {
 // Engine options
 auto num_tt_entries = 64ULL << 15;  // The first value is the size in megabytes
 auto thread_count = 1;
+// Possible tournament settings (4095 bytes exe)
+// auto num_tt_entries = 1ULL << 30;  // 32 GB
+// auto thread_count = 52;
 
 vector<TT_Entry> transposition_table;
 
@@ -316,8 +322,9 @@ void generate_piece_moves(Move *const movelist,
     const BB all = pos.colour[0] | pos.colour[1];
     const BB to_mask = only_captures ? pos.colour[1] : ~pos.colour[0];
     const BB pawns = pos.colour[0] & pos.pieces[Pawn];
+    generate_pawn_moves(
+        movelist, num_moves, north(pawns) & ~all & (only_captures ? 0xFF00000000000000ULL : 0xFFFFFFFFFFFF0000ULL), -8);
     if (!only_captures) {
-        generate_pawn_moves(movelist, num_moves, north(pawns) & ~all, -8);
         generate_pawn_moves(movelist, num_moves, north(north(pawns & 0xFF00ULL) & ~all) & ~all, -16);
     }
     generate_pawn_moves(movelist, num_moves, nw(pawns) & (pos.colour[1] | pos.ep), -7);
@@ -468,6 +475,13 @@ const int pawn_attacked[] = {S(-61, -18), S(-53, -42)};
             }
         }
 
+        // Bad bishops
+        score -= S(4, 4)
+            * ((!!(pos.colour[0] & pos.pieces[Bishop] & 0xAA55AA55AA55AA55ULL)
+               * count(pawns[0] & 0xAA55AA55AA55AA55ULL))
+            + (!!(pos.colour[0] & pos.pieces[Bishop] & ~0xAA55AA55AA55AA55ULL)
+               * count(pawns[0] & ~0xAA55AA55AA55AA55ULL)));
+
         flip(pos);
 
         score = -score;
@@ -514,16 +528,15 @@ int alphabeta(Position &pos,
               vector<BB> &hash_history,
               const int do_null = true) {
     const int static_eval = eval(pos);
-
     // Don't overflow the stack
     if (ply > 127) {
         return static_eval;
     }
-
+    stack[ply].score = static_eval;
     // Check extensions
     const auto in_check = attacked(pos, lsb(pos.colour[0] & pos.pieces[King]));
     depth = in_check ? max(1, depth + 1) : depth;
-
+    const int improving = ply > 1 && static_eval > stack[ply - 2].score;
     const int in_qsearch = depth <= 0;
     if (in_qsearch && static_eval > alpha) {
         if (static_eval >= beta) {
@@ -545,8 +558,8 @@ int alphabeta(Position &pos,
         if (!in_check && alpha == beta - 1) {
             // Reverse futility pruning
             if (depth < 5) {
-                const int margins[] = {0, 50, 100, 200, 300};
-                if (static_eval - margins[depth] >= beta) {
+                const int margins[] = {50, 50, 100, 200, 300};
+                if (static_eval - margins[depth - improving] >= beta) {
                     return beta;
                 }
             }
@@ -635,6 +648,7 @@ int alphabeta(Position &pos,
         }
     }
 
+    int quiet_moves_evaluated = 0;
     int moves_evaluated = 0;
     int best_score = -INF;
     Move best_move{};
@@ -722,15 +736,17 @@ int alphabeta(Position &pos,
                 goto full_window;
             }
         }
+        moves_evaluated++;
+        if (piece_on(pos, move.to) == None) {
+            quiet_moves_evaluated++;
+        }
 
         // Exit early if out of time
         if (stop || now() >= stop_time) {
             hash_history.pop_back();
             return 0;
         }
 
-        moves_evaluated++;
-
         if (score > best_score) {
             best_score = score;
             best_move = move;
@@ -754,6 +770,11 @@ int alphabeta(Position &pos,
             }
             break;
         }
+
+        // Late move pruning based on quiet move count
+        if (!in_check && alpha == beta - 1 && quiet_moves_evaluated > 3 + 2 * depth * depth) {
+            break;
+        }
     }
     hash_history.pop_back();