KnightStackSys · Oct 9, 2026 · Oct 9, 2026
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -24,6 +24,7 @@ add_library(ironphoenix_core STATIC
     src/tt.cpp
     src/eval.cpp
     src/nnue.cpp
+    src/tuning.cpp
     src/search.cpp
     src/multipv.cpp
     src/fen.cpp
@@ -33,6 +34,7 @@ add_library(ironphoenix_core STATIC
     include/ironphoenix/eval.hpp
     include/ironphoenix/lmr.hpp
     include/ironphoenix/nnue.hpp
+    include/ironphoenix/tuning.hpp
 )
 
 add_library(IronPhoenix::Core ALIAS ironphoenix_core)

diff --git a/include/ironphoenix/eval.hpp b/include/ironphoenix/eval.hpp
@@ -1,15 +1,16 @@
 #pragma once
 
+#include "tuning.hpp"
+
 namespace ironphoenix {
 
     class Position;
 
     namespace Eval {
 
-        struct Parameters final {
-
-        };
+        using Parameters = Tuning::EvalParameters;
 
+        [[nodiscard]] Parameters& parameters() noexcept;
         [[nodiscard]] int evaluate(const Position& pos) noexcept;
 
     }

diff --git a/include/ironphoenix/lmr.hpp b/include/ironphoenix/lmr.hpp
@@ -12,7 +12,10 @@ namespace ironphoenix {
         std::array<std::array<std::uint8_t, LMR_MAX_MOVES + 1>,
         LMR_MAX_DEPTH + 1>;
 
-    extern const LmrReductionTable lmrReduction;
+    // The table is rebuilt whenever an LMR tuning parameter changes.
+    extern LmrReductionTable lmrReduction;
+
+    void rebuildLmrReductionTable() noexcept;
 
     inline int lmrBaseReduction(int depth, int moveCount) noexcept {
         if (depth <= 0 || moveCount <= 0)

diff --git a/include/ironphoenix/tuning.hpp b/include/ironphoenix/tuning.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <iosfwd>
+#include <string_view>
+
+namespace ironphoenix {
+
+    class SearchEngine;
+
+    namespace Tuning {
+
+        struct SearchParameters final {
+            int aspirationStartDepth = 4;
+            int aspirationInitialDelta = 50;
+            int seePruneMaxDepth = 4;
+            int seePruneMarginPerDepth = 80;
+            int historyBonusScale = 64;
+            int historyBonusMax = 2048;
+            int counterMoveBonus = 32'000;
+            int checkMoveBonus = 10'000'000;
+            int lmrMinDepth = 3;
+            int lmrFullMoves = 3;
+            int lmrBaseX100 = 75;
+            int lmrDivisorX100 = 275;
+        };
+
+        struct EvalParameters final {
+            int pawnValue = 100;
+            int knightValue = 300;
+            int bishopValue = 400;
+            int rookValue = 500;
+            int queenValue = 1000;
+            int knightMobility = 4;
+            int bishopMobility = 4;
+            int rookMobility = 2;
+            int queenMobility = 1;
+        };
+
+        [[nodiscard]] SearchParameters& search() noexcept;
+        [[nodiscard]] EvalParameters& eval() noexcept;
+
+        void resetSearch() noexcept;
+        void resetEval() noexcept;
+        void resetAll() noexcept;
+
+        [[nodiscard]] bool setSearchParameter(std::string_view name, int value) noexcept;
+        [[nodiscard]] bool setEvalParameter(std::string_view name, int value) noexcept;
+
+        // UCI integration helpers. handleSetOption returns true when the option
+        // belongs to the tuning system, including recognized-but-invalid input.
+        [[nodiscard]] bool handleSetOption(std::string_view args, SearchEngine& searchEngine, std::ostream& out);
+        void printUciOptions(std::ostream& out);
+        void printCurrent(std::ostream& out);
+
+    } // namespace Tuning
+
+} // namespace ironphoenix
diff --git a/src/eval.cpp b/src/eval.cpp
@@ -3,20 +3,36 @@
 #include "ironphoenix/geometry.hpp"
 #include "ironphoenix/nnue.hpp"
 #include "ironphoenix/position.hpp"
-
-#include <array>
+#include "ironphoenix/tuning.hpp"
 
 namespace ironphoenix::Eval {
 
     namespace {
 
-        constexpr std::array<int, PIECE_TYPE_NB> EVAL_VALUE = {
-            0, 100, 300, 400, 500, 1000, 0
-        };
+        IRONPHOENIX_FORCE_INLINE int evalValue(PieceType pt) noexcept {
+            const auto& params = Tuning::eval();
 
-        constexpr std::array<int, PIECE_TYPE_NB> MOBILITY_WEIGHT = {
-            0, 0, 4, 4, 2, 1, 0
-        };
+            switch (pt) {
+            case PAWN:   return params.pawnValue;
+            case KNIGHT: return params.knightValue;
+            case BISHOP: return params.bishopValue;
+            case ROOK:   return params.rookValue;
+            case QUEEN:  return params.queenValue;
+            default:     return 0;
+            }
+        }
+
+        IRONPHOENIX_FORCE_INLINE int mobilityWeight(PieceType pt) noexcept {
+            const auto& params = Tuning::eval();
+
+            switch (pt) {
+            case KNIGHT: return params.knightMobility;
+            case BISHOP: return params.bishopMobility;
+            case ROOK:   return params.rookMobility;
+            case QUEEN:  return params.queenMobility;
+            default:     return 0;
+            }
+        }
 
         IRONPHOENIX_FORCE_INLINE Bitboard teamOccupancy(const Position& pos, Color c) noexcept {
             const Color partner = static_cast<Color>(static_cast<unsigned>(c) ^ 2u);
@@ -28,7 +44,7 @@ namespace ironphoenix::Eval {
 
             for (unsigned pt = PAWN; pt <= QUEEN; ++pt) {
                 material += pos.pieces(c, static_cast<PieceType>(pt)).popcount()
-                    * EVAL_VALUE[pt];
+                    * evalValue(static_cast<PieceType>(pt));
             }
 
             return material;
@@ -65,7 +81,7 @@ namespace ironphoenix::Eval {
                     }
 
                     const int mobility = (attacks & ~blockedByTeam).popcount();
-                    score += mobility * MOBILITY_WEIGHT[static_cast<unsigned>(pt)];
+                    score += mobility * mobilityWeight(pt);
                 }
             };
 
@@ -102,6 +118,10 @@ namespace ironphoenix::Eval {
 
     }
 
+    Parameters& parameters() noexcept {
+        return Tuning::eval();
+    }
+
     int evaluate(const Position& pos) noexcept {
         if (NNUE::loaded())
             return NNUE::evaluate(pos);

diff --git a/src/lmr.cpp b/src/lmr.cpp
@@ -1,4 +1,5 @@
 #include "ironphoenix/lmr.hpp"
+#include "ironphoenix/tuning.hpp"
 
 #include <algorithm>
 #include <cmath>
@@ -7,26 +8,29 @@ namespace ironphoenix {
 
     namespace {
 
-        LmrReductionTable buildLmrReductionTable() {
+        LmrReductionTable buildLmrReductionTable() noexcept {
             LmrReductionTable table{};
+            const auto& params = Tuning::search();
+
+            const double base = static_cast<double>(params.lmrBaseX100) / 100.0;
+            const double divisor = static_cast<double>(std::max(1, params.lmrDivisorX100)) / 100.0;
 
             for (int depth = 1; depth <= LMR_MAX_DEPTH; ++depth) {
                 for (int moveCount = 1; moveCount <= LMR_MAX_MOVES; ++moveCount) {
 
-                    if (depth < 3 || moveCount <= 3) {
+                    if (depth < params.lmrMinDepth || moveCount <= params.lmrFullMoves) {
                         table[depth][moveCount] = 0;
                         continue;
                     }
-                    
+
                     const double raw =
-                        0.75
+                        base
                         + (std::log(static_cast<double>(depth))
-                            * std::log(static_cast<double>(moveCount))) / 2.75;
+                            * std::log(static_cast<double>(moveCount))) / divisor;
 
                     int reduction = static_cast<int>(raw);
 
                     reduction = std::max(reduction, 1);
-
                     reduction = std::min(reduction, std::max(1, depth - 2));
 
                     table[depth][moveCount] =
@@ -39,6 +43,10 @@ namespace ironphoenix {
 
     }
 
-    const LmrReductionTable lmrReduction = buildLmrReductionTable();
+    LmrReductionTable lmrReduction = buildLmrReductionTable();
+
+    void rebuildLmrReductionTable() noexcept {
+        lmrReduction = buildLmrReductionTable();
+    }
 
 }
diff --git a/src/search.cpp b/src/search.cpp
@@ -2,6 +2,7 @@
 
 #include "ironphoenix/eval.hpp"
 #include "ironphoenix/lmr.hpp"
+#include "ironphoenix/tuning.hpp"
 
 #include "ironphoenix/movegen.hpp"
 #include "ironphoenix/see.hpp"
@@ -15,13 +16,6 @@
 namespace ironphoenix {
     namespace {
 
-        constexpr int ASPIRATION_START_DEPTH = 4;
-        constexpr int ASPIRATION_INITIAL_DELTA = 50;
-
-        constexpr int SEE_PRUNE_MAX_DEPTH = 4;
-        constexpr int SEE_PRUNE_MARGIN_PER_DEPTH = 80;
-        constexpr int QSEARCH_SEE_THRESHOLD = -50;
-
         IRONPHOENIX_FORCE_INLINE Bitboard teamOccupancy(const Position& pos, Color c) noexcept {
             const Color partner = static_cast<Color>(static_cast<unsigned>(c) ^ 2u);
             return pos.occupancy(c) | pos.occupancy(partner);
@@ -124,7 +118,8 @@ namespace ironphoenix {
     }
 
     int SearchEngine::historyBonus(int depth) const noexcept {
-        return std::min(2048, 64 * depth * depth);
+        const auto& params = Tuning::search();
+        return std::min(params.historyBonusMax, params.historyBonusScale * depth * depth);
     }
 
     int SearchEngine::moveScore(const Position& pos, Move move, Move ttMove, int ply) const noexcept {
@@ -133,6 +128,7 @@ namespace ironphoenix {
         if (isTerminalKingCapture(pos, move))
             return 45'000'000;
 
+        const auto& tuning = Tuning::search();
         const Color mover = pos.sideToMove();
         const Piece movingPiece = pos.pieceAt(move.from());
 
@@ -158,7 +154,7 @@ namespace ironphoenix {
             score += history_.continuationScore(ContinuationKind::PreviousPly, searchStack_[ply], movingPiece, move.to());
 
             if (history_.counterMove(mover, searchStack_[ply]) == move)
-                score += 32'000;
+                score += tuning.counterMoveBonus;
         }
 
         if (ply >= 4 && searchStack_[ply - 3].valid()
@@ -167,7 +163,7 @@ namespace ironphoenix {
         }
 
         if (pos.givesCheck(move))
-            score += 10'000'000;
+            score += tuning.checkMoveBonus;
 
         return score;
     }
@@ -413,6 +409,7 @@ namespace ironphoenix {
         }
 
         const bool inCheckNode = pos.inCheck();
+        const auto& tuning = Tuning::search();
 
         MoveList moves;
         generatePseudoLegalMoves(pos, moves);
@@ -446,14 +443,14 @@ namespace ironphoenix {
 
             if (!pvNode
                 && !inCheckNode
-                && depth <= SEE_PRUNE_MAX_DEPTH
+                && depth <= tuning.seePruneMaxDepth
                 && legalMoves > 0
                 && move.isCapture()
                 && !move.isPromotion()
                 && move != ttMove
                 && !givesCheckMove
                 && !mateWindow) {
-                const int seeThreshold = -SEE_PRUNE_MARGIN_PER_DEPTH * depth;
+                const int seeThreshold = -tuning.seePruneMarginPerDepth * depth;
                 if (!seeGE(pos, move, seeThreshold, SeeMode::Legal))
                     continue;
             }
@@ -654,6 +651,7 @@ namespace ironphoenix {
             return;
         }
 
+        const auto& tuning = Tuning::search();
         const int requestedDepth = limits_.depth > 0 ? std::min(limits_.depth, MAX_PLY - 1) : 0;
         int depth = 1;
 
@@ -669,7 +667,7 @@ namespace ironphoenix {
 
             int score = 0;
 
-            if (depth < ASPIRATION_START_DEPTH ||
+            if (depth < tuning.aspirationStartDepth ||
                 bestScore >= MATE_THRESHOLD ||
                 bestScore <= -MATE_THRESHOLD)
             {
@@ -686,7 +684,7 @@ namespace ironphoenix {
             }
             else
             {
-                int delta = ASPIRATION_INITIAL_DELTA;
+                int delta = tuning.aspirationInitialDelta;
 
                 int alpha = std::max(-INF, bestScore - delta);
                 int beta = std::min(INF, bestScore + delta);