Update correction history in case of successful null move pruning

Since null move pruning uses the same position it makes some sense to try to update correction history there in case of fail high.
Update value is 4 times less than normal update.

Passed STC:
https://tests.stockfishchess.org/tests/view/664a011cae57c1758ac5b4dd
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 419360 W: 108390 L: 107505 D: 203465
Ptnml(0-2): 1416, 49603, 106724, 50554, 1383

Passed LTC:
https://tests.stockfishchess.org/tests/view/664a53d95fc7b70b8817c65b
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 193518 W: 49076 L: 48434 D: 96008
Ptnml(0-2): 89, 21335, 53263, 21989, 83

closes https://github.com/official-stockfish/Stockfish/pull/5272

bench 1301487

diff --git a/src/nnue/nnue_misc.cpp b/src/nnue/nnue_misc.cpp
index b54bbaba3ddbbdd9c3900415290cc03a224a9395..a13c717c3d80990a5af55523543f7016063eb8e8 100644 (file)
--- a/src/nnue/nnue_misc.cpp
+++ b/src/nnue/nnue_misc.cpp
@@ -178,11 +178,14 @@ trace(Position& pos, const Eval::NNUE::Networks& networks, Eval::NNUE::Accumulat
         ss << "|  " << bucket << "        ";
         ss << " |  ";
         format_cp_aligned_dot(t.psqt[bucket], ss, pos);
-        ss << "  " << " |  ";
+        ss << "  "
+           << " |  ";
         format_cp_aligned_dot(t.positional[bucket], ss, pos);
-        ss << "  " << " |  ";
+        ss << "  "
+           << " |  ";
         format_cp_aligned_dot(t.psqt[bucket] + t.positional[bucket], ss, pos);
-        ss << "  " << " |";
+        ss << "  "
+           << " |";
         if (bucket == t.correctBucket)
             ss << " <-- this bucket is used";
         ss << '\n';

diff --git a/src/search.cpp b/src/search.cpp
index 7e95dd878c31f16feb68c40e38e56a0a4ed26c47..2ed5d97bb5d5f2fb99004f2ef3d5ce15418ba6d1 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -802,7 +802,16 @@ Value Search::Worker::search(
         if (nullValue >= beta && nullValue < VALUE_TB_WIN_IN_MAX_PLY)
         {
             if (thisThread->nmpMinPly || depth < 16)
+            {
+                if (nullValue >= ss->staticEval)
+                {
+                    auto bonus = std::min(int(nullValue - ss->staticEval) * depth / 32,
+                                          CORRECTION_HISTORY_LIMIT / 16);
+                    thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+                      << bonus;
+                }
                 return nullValue;
+            }
 
             assert(!thisThread->nmpMinPly);  // Recursive verification is not allowed