Remove classical psqt

Based on vondele's deletepsqt branch:
https://github.com/vondele/Stockfish/commit/369f5b051

This huge simplification uses a weighted material differences instead of
the positional piece square tables (psqt) in the semi-classical complexity
calculation. Tuned weights using spsa at 45+0.45 with:

int pawnMult = 100;
int knightMult = 325;
int bishopMult = 350;
int rookMult = 500;
int queenMult = 900;
TUNE(SetRange(0, 200), pawnMult);
TUNE(SetRange(0, 650), knightMult);
TUNE(SetRange(0, 700), bishopMult);
TUNE(SetRange(200, 800), rookMult);
TUNE(SetRange(600, 1200), queenMult);

The values obtained via this tuning session were for a model where
the psqt replacement formula was always from the point of view of White,
even if the side to move was Black. We re-used the same values for an
implementation with a psqt replacement from the point of view of the side
to move, testing the result both on our standard book on positions with
a strong White bias, and an alternate book with positions with a strong
Black bias.

We note that with the patch the last use of the venerable "Score" type
disappears in Stockfish codebase (the Score type was used in classical
evaluation to get a tampered eval interpolating values smoothly from the
early midgame stage to the endgame stage). We leave it to another commit
to clean all occurrences of Score in the code and the comments.

-------

Passed non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 142542 W: 36264 L: 36168 D: 70110
Ptnml(0-2): 76, 15578, 39856, 15696, 65
https://tests.stockfishchess.org/tests/view/64c8cb495b17f7c21c0cf9f8

Passed non-regression LTC (with a book with Black bias):
https://tests.stockfishchess.org/tests/view/64c8f9295b17f7c21c0cfdaf
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 494814 W: 125565 L: 125827 D: 243422
Ptnml(0-2): 244, 53926, 139346, 53630, 261

------

closes https://github.com/official-stockfish/Stockfish/pull/4713

Bench: 1655985

diff --git a/src/Makefile b/src/Makefile
index f66d84d5547fe396b458604de939c7204cfa8931..8811d15e8689689bd4273ff5bd6d3acb4fb79869 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -53,7 +53,7 @@ PGOBENCH = $(WINE_PATH) ./$(EXE) bench
 
 ### Source and object files
 SRCS = benchmark.cpp bitboard.cpp evaluate.cpp main.cpp \
-       misc.cpp movegen.cpp movepick.cpp position.cpp psqt.cpp \
+       misc.cpp movegen.cpp movepick.cpp position.cpp \
        search.cpp thread.cpp timeman.cpp tt.cpp uci.cpp ucioption.cpp tune.cpp syzygy/tbprobe.cpp \
        nnue/evaluate_nnue.cpp nnue/features/half_ka_v2_hm.cpp
 

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 7f0ea4bc6040c4d38d0958fe0b3e61eeafe5a5de..c37dd98ad1c257a892930ca42385a0a2642fb5f0 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -143,7 +143,6 @@ Value Eval::evaluate(const Position& pos) {
   assert(!pos.checkers());
 
   Value v;
-  Value psq = pos.psq_eg_stm();
 
   int nnueComplexity;
   int npm = pos.non_pawn_material() / 64;
@@ -153,8 +152,14 @@ Value Eval::evaluate(const Position& pos) {
 
   Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
 
+  int material =   67 * (pos.count<PAWN>(stm)   - pos.count<PAWN>(~stm))
+                + 395 * (pos.count<KNIGHT>(stm) - pos.count<KNIGHT>(~stm))
+                + 288 * (pos.count<BISHOP>(stm) - pos.count<BISHOP>(~stm))
+                + 630 * (pos.count<ROOK>(stm)   - pos.count<ROOK>(~stm))
+                + 857 * (pos.count<QUEEN>(stm)  - pos.count<QUEEN>(~stm));
+
   // Blend optimism with nnue complexity and (semi)classical complexity
-  optimism += optimism * (nnueComplexity + abs(psq - nnue)) / 512;
+  optimism += optimism * (nnueComplexity + abs(material - nnue)) / 512;
 
   v = (  nnue     * (915 + npm + 9 * pos.count<PAWN>())
        + optimism * (154 + npm +     pos.count<PAWN>())) / 1024;

diff --git a/src/main.cpp b/src/main.cpp
index 593408f63a7d978a23e4cfb81bf70e44cafcdea0..c854ac0cd1644584800dcd8483b0baf5483f7e69 100644 (file)
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -20,7 +20,6 @@
 
 #include "bitboard.h"
 #include "position.h"
-#include "psqt.h"
 #include "search.h"
 #include "syzygy/tbprobe.h"
 #include "thread.h"
@@ -36,7 +35,6 @@ int main(int argc, char* argv[]) {
   CommandLine::init(argc, argv);
   UCI::init(Options);
   Tune::init();
-  PSQT::init();
   Bitboards::init();
   Position::init();
   Threads.set(size_t(Options["Threads"]));

diff --git a/src/position.h b/src/position.h
index dc4c583729970a6e66c917a6e5dc946566db23a3..393c1ac9226ade4e18c40d54dcce040298fed3b7 100644 (file)
--- a/src/position.h
+++ b/src/position.h
@@ -26,7 +26,6 @@
 
 #include "bitboard.h"
 #include "evaluate.h"
-#include "psqt.h"
 #include "types.h"
 
 #include "nnue/nnue_accumulator.h"
@@ -153,7 +152,6 @@ public:
   bool has_game_cycle(int ply) const;
   bool has_repeated() const;
   int rule50_count() const;
-  Value psq_eg_stm() const;
   Value non_pawn_material(Color c) const;
   Value non_pawn_material() const;
 
@@ -192,7 +190,6 @@ private:
   StateInfo* st;
   int gamePly;
   Color sideToMove;
-  Score psq;
   bool chess960;
 };
 
@@ -321,10 +318,6 @@ inline Key Position::material_key() const {
   return st->materialKey;
 }
 
-inline Value Position::psq_eg_stm() const {
-  return (sideToMove == WHITE ? 1 : -1) * eg_value(psq);
-}
-
 inline Value Position::non_pawn_material(Color c) const {
   return st->nonPawnMaterial[c];
 }
@@ -374,7 +367,6 @@ inline void Position::put_piece(Piece pc, Square s) {
   byColorBB[color_of(pc)] |= s;
   pieceCount[pc]++;
   pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
-  psq += PSQT::psq[pc][s];
 }
 
 inline void Position::remove_piece(Square s) {
@@ -386,7 +378,6 @@ inline void Position::remove_piece(Square s) {
   board[s] = NO_PIECE;
   pieceCount[pc]--;
   pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
-  psq -= PSQT::psq[pc][s];
 }
 
 inline void Position::move_piece(Square from, Square to) {
@@ -398,7 +389,6 @@ inline void Position::move_piece(Square from, Square to) {
   byColorBB[color_of(pc)] ^= fromTo;
   board[from] = NO_PIECE;
   board[to] = pc;
-  psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
 }
 
 inline void Position::do_move(Move m, StateInfo& newSt) {

diff --git a/src/psqt.cpp b/src/psqt.cpp
deleted file mode 100644 (file)
index d3ebb20..0000000
--- a/src/psqt.cpp
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
-  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
-
-  Stockfish is free software: you can redistribute it and/or modify
-  it under the terms of the GNU General Public License as published by
-  the Free Software Foundation, either version 3 of the License, or
-  (at your option) any later version.
-
-  Stockfish is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-  GNU General Public License for more details.
-
-  You should have received a copy of the GNU General Public License
-  along with this program.  If not, see <http://www.gnu.org/licenses/>.
-*/
-
-
-#include "psqt.h"
-
-#include <algorithm>
-
-#include "bitboard.h"
-#include "types.h"
-
-namespace Stockfish {
-
-namespace
-{
-
-auto constexpr S = make_score;
-
-// 'Bonus' contains Piece-Square parameters.
-// Scores are explicit for files A to D, implicitly mirrored for E to H.
-constexpr Score Bonus[][RANK_NB][int(FILE_NB) / 2] = {
-  { },
-  { },
-  { // Knight
-   { S(-175, -96), S(-92,-65), S(-74,-49), S(-73,-21) },
-   { S( -77, -67), S(-41,-54), S(-27,-18), S(-15,  8) },
-   { S( -61, -40), S(-17,-27), S(  6, -8), S( 12, 29) },
-   { S( -35, -35), S(  8, -2), S( 40, 13), S( 49, 28) },
-   { S( -34, -45), S( 13,-16), S( 44,  9), S( 51, 39) },
-   { S(  -9, -51), S( 22,-44), S( 58,-16), S( 53, 17) },
-   { S( -67, -69), S(-27,-50), S(  4,-51), S( 37, 12) },
-   { S(-201,-100), S(-83,-88), S(-56,-56), S(-26,-17) }
-  },
-  { // Bishop
-   { S(-37,-40), S(-4 ,-21), S( -6,-26), S(-16, -8) },
-   { S(-11,-26), S(  6, -9), S( 13,-12), S(  3,  1) },
-   { S(-5 ,-11), S( 15, -1), S( -4, -1), S( 12,  7) },
-   { S(-4 ,-14), S(  8, -4), S( 18,  0), S( 27, 12) },
-   { S(-8 ,-12), S( 20, -1), S( 15,-10), S( 22, 11) },
-   { S(-11,-21), S(  4,  4), S(  1,  3), S(  8,  4) },
-   { S(-12,-22), S(-10,-14), S(  4, -1), S(  0,  1) },
-   { S(-34,-32), S(  1,-29), S(-10,-26), S(-16,-17) }
-  },
-  { // Rook
-   { S(-31, -9), S(-20,-13), S(-14,-10), S(-5, -9) },
-   { S(-21,-12), S(-13, -9), S( -8, -1), S( 6, -2) },
-   { S(-25,  6), S(-11, -8), S( -1, -2), S( 3, -6) },
-   { S(-13, -6), S( -5,  1), S( -4, -9), S(-6,  7) },
-   { S(-27, -5), S(-15,  8), S( -4,  7), S( 3, -6) },
-   { S(-22,  6), S( -2,  1), S(  6, -7), S(12, 10) },
-   { S( -2,  4), S( 12,  5), S( 16, 20), S(18, -5) },
-   { S(-17, 18), S(-19,  0), S( -1, 19), S( 9, 13) }
-  },
-  { // Queen
-   { S( 3,-69), S(-5,-57), S(-5,-47), S( 4,-26) },
-   { S(-3,-54), S( 5,-31), S( 8,-22), S(12, -4) },
-   { S(-3,-39), S( 6,-18), S(13, -9), S( 7,  3) },
-   { S( 4,-23), S( 5, -3), S( 9, 13), S( 8, 24) },
-   { S( 0,-29), S(14, -6), S(12,  9), S( 5, 21) },
-   { S(-4,-38), S(10,-18), S( 6,-11), S( 8,  1) },
-   { S(-5,-50), S( 6,-27), S(10,-24), S( 8, -8) },
-   { S(-2,-74), S(-2,-52), S( 1,-43), S(-2,-34) }
-  },
-  { // King
-   { S(271,  1), S(327, 45), S(271, 85), S(198, 76) },
-   { S(278, 53), S(303,100), S(234,133), S(179,135) },
-   { S(195, 88), S(258,130), S(169,169), S(120,175) },
-   { S(164,103), S(190,156), S(138,172), S( 98,172) },
-   { S(154, 96), S(179,166), S(105,199), S( 70,199) },
-   { S(123, 92), S(145,172), S( 81,184), S( 31,191) },
-   { S( 88, 47), S(120,121), S( 65,116), S( 33,131) },
-   { S( 59, 11), S( 89, 59), S( 45, 73), S( -1, 78) }
-  }
-};
-
-constexpr Score PBonus[RANK_NB][FILE_NB] =
-  { // Pawn (asymmetric distribution)
-   { },
-   { S(  2, -8), S(  4, -6), S( 11,  9), S( 18,  5), S( 16, 16), S( 21,  6), S(  9, -6), S( -3,-18) },
-   { S( -9, -9), S(-15, -7), S( 11,-10), S( 15,  5), S( 31,  2), S( 23,  3), S(  6, -8), S(-20, -5) },
-   { S( -3,  7), S(-20,  1), S(  8, -8), S( 19, -2), S( 39,-14), S( 17,-13), S(  2,-11), S( -5, -6) },
-   { S( 11, 12), S( -4,  6), S(-11,  2), S(  2, -6), S( 11, -5), S(  0, -4), S(-12, 14), S(  5,  9) },
-   { S(  3, 27), S(-11, 18), S( -6, 19), S( 22, 29), S( -8, 30), S( -5,  9), S(-14,  8), S(-11, 14) },
-   { S( -7, -1), S(  6,-14), S( -2, 13), S(-11, 22), S(  4, 24), S(-14, 17), S( 10,  7), S( -9,  7) }
-  };
-
-} // namespace
-
-
-namespace PSQT
-{
-
-Score psq[PIECE_NB][SQUARE_NB];
-
-// PSQT::init() initializes piece-square tables: the white halves of the tables are
-// copied from Bonus[] and PBonus[], adding the piece value, then the black halves of
-// the tables are initialized by flipping and changing the sign of the white scores.
-void init() {
-
-  for (Piece pc : {W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING})
-  {
-    Score score = make_score(PieceValue[MG][pc], PieceValue[EG][pc]);
-
-    for (Square s = SQ_A1; s <= SQ_H8; ++s)
-    {
-      File f = File(edge_distance(file_of(s)));
-      psq[ pc][s] = score + (type_of(pc) == PAWN ? PBonus[rank_of(s)][file_of(s)]
-                                                 : Bonus[pc][rank_of(s)][f]);
-      psq[~pc][flip_rank(s)] = -psq[pc][s];
-    }
-  }
-}
-
-} // namespace PSQT
-
-} // namespace Stockfish

diff --git a/src/psqt.h b/src/psqt.h
deleted file mode 100644 (file)
index 9630f44..0000000
--- a/src/psqt.h
+++ /dev/null
@@ -1,38 +0,0 @@
-/*
-  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
-
-  Stockfish is free software: you can redistribute it and/or modify
-  it under the terms of the GNU General Public License as published by
-  the Free Software Foundation, either version 3 of the License, or
-  (at your option) any later version.
-
-  Stockfish is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-  GNU General Public License for more details.
-
-  You should have received a copy of the GNU General Public License
-  along with this program.  If not, see <http://www.gnu.org/licenses/>.
-*/
-
-
-#ifndef PSQT_H_INCLUDED
-#define PSQT_H_INCLUDED
-
-
-#include "types.h"
-
-
-namespace Stockfish::PSQT
-{
-
-extern Score psq[PIECE_NB][SQUARE_NB];
-
-// Fill psqt array from a set of internally linked parameters
-void init();
-
-} // namespace Stockfish::PSQT
-
-
-#endif // PSQT_H_INCLUDED