From f0de8dc0349bac56021a900910f14a00a729dbc6 Mon Sep 17 00:00:00 2001
From: Carlos Esparza <ca2010es@gmail.com>
Date: Mon, 21 Apr 2025 18:26:46 -0700
Subject: [PATCH] Simplify move ordering bonuses for putting piece en prise and
 escaping capture

Now there is also a penalty for exposing knights and bishops to capture by a pawn.

Passed STC:
https://tests.stockfishchess.org/tests/view/68074379878abf56f9a0d5b1
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 96512 W: 24841 L: 24687 D: 46984
Ptnml(0-2): 294, 11336, 24835, 11504, 287

Passed LTC:
https://tests.stockfishchess.org/tests/view/6808954a878abf56f9a0d76d
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 221328 W: 56271 L: 56255 D: 108802
Ptnml(0-2): 131, 24149, 62071, 24199, 114

closes https://github.com/official-stockfish/Stockfish/pull/6023

Bench: 1778227
---
 src/movepick.cpp | 37 +++++++++++++++++--------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/src/movepick.cpp b/src/movepick.cpp
index cac4abe4a..71a5f9959 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -126,21 +126,20 @@ void MovePicker::score() {
 
     static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
 
-    [[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook,
-      threatenedPieces;
+    [[maybe_unused]] Bitboard threatenedPieces, threatByLesser[4];
     if constexpr (Type == QUIETS)
     {
         Color us = pos.side_to_move();
 
-        threatenedByPawn = pos.attacks_by<PAWN>(~us);
-        threatenedByMinor =
-          pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatenedByPawn;
-        threatenedByRook = pos.attacks_by<ROOK>(~us) | threatenedByMinor;
+        threatByLesser[0] = threatByLesser[1] = pos.attacks_by<PAWN>(~us);
+        threatByLesser[2] =
+          pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatByLesser[0];
+        threatByLesser[3] = pos.attacks_by<ROOK>(~us) | threatByLesser[2];
 
         // Pieces threatened by pieces of lesser material value
-        threatenedPieces = (pos.pieces(us, QUEEN) & threatenedByRook)
-                         | (pos.pieces(us, ROOK) & threatenedByMinor)
-                         | (pos.pieces(us, KNIGHT, BISHOP) & threatenedByPawn);
+        threatenedPieces = (pos.pieces(us, QUEEN) & threatByLesser[3])
+                         | (pos.pieces(us, ROOK) & threatByLesser[2])
+                         | (pos.pieces(us, KNIGHT, BISHOP) & threatByLesser[0]);
     }
 
     for (auto& m : *this)
@@ -172,17 +171,15 @@ void MovePicker::score() {
             // bonus for checks
             m.value += (bool(pos.check_squares(pt) & to) && pos.see_ge(m, -75)) * 16384;
 
-            // bonus for escaping from capture
-            m.value += threatenedPieces & from ? (pt == QUEEN && !(to & threatenedByRook)   ? 51700
-                                                  : pt == ROOK && !(to & threatenedByMinor) ? 25600
-                                                  : !(to & threatenedByPawn)                ? 14450
-                                                                                            : 0)
-                                               : 0;
-
-            // malus for putting piece en prise
-            m.value -= (pt == QUEEN && bool(to & threatenedByRook)   ? 49000
-                        : pt == ROOK && bool(to & threatenedByMinor) ? 24335
-                                                                     : 0);
+            // penalty for moving to a square threatened by a lesser piece
+            // or bonus for escaping an attack by a lesser piece.
+            constexpr int bonus[4] = {144, 144, 256, 517};
+            if (KNIGHT <= pt && pt <= QUEEN)
+            {
+                auto i = pt - 2;
+                int  v = (threatByLesser[i] & to ? -95 : 100 * bool(threatByLesser[i] & from));
+                m.value += bonus[i] * v;
+            }
 
             if (ply < LOW_PLY_HISTORY_SIZE)
                 m.value += 8 * (*lowPlyHistory)[ply][m.from_to()] / (1 + 2 * ply);