From dabffbceffee2e68352bf5865987d5b2a91ce410 Mon Sep 17 00:00:00 2001
From: Michael Chaly <Vizvezdenec@gmail.com>
Date: Sun, 2 Feb 2025 06:06:13 +0300
Subject: [PATCH] Make pruning at ttpv nodes more aggressive
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Continuation of work done by @FauziAkram and @Viren6 They had a series
of patches that decrease pruning for ttPv nodes - and it passed as a
gainer at lower time controls while revert passed as a gainer at higher
time controls.
So it's a logical continuation of this work that increases pruning for
ttPv nodes in hopes of scaling to longer TCs.

Fixed games STC:
https://tests.stockfishchess.org/tests/view/679ee3910774dfd78deb0efd
Elo: -4.98 ± 2.1 (95%) LOS: 0.0%
Total: 28584 W: 7229 L: 7639 D: 13716
Ptnml(0-2): 143, 3579, 7219, 3247, 104
nElo: -9.54 ± 4.0 (95%) PairsRatio: 0.90

Passed VVLTC with STC bounds:
https://tests.stockfishchess.org/tests/view/679d21f70774dfd78deaf553
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 323282 W: 83729 L: 83105 D: 156448
Ptnml(0-2): 37, 29842, 101269, 30446, 47

Passed VVLTC with LTC bounds:
https://tests.stockfishchess.org/tests/view/679e7a970774dfd78deb0cd3
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 113712 W: 29485 L: 29051 D: 55176
Ptnml(0-2): 13, 10376, 35640, 10818, 9

closes https://github.com/official-stockfish/Stockfish/pull/5844

Bench: 2964045
---
 src/search.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 9af7a115..60f716cd 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -999,6 +999,12 @@ moves_loop:  // When in check, search starts here
 
         Depth r = reduction(improving, depth, moveCount, delta);
 
+        // Increase reduction for ttPv nodes (*Scaler)
+        // Smaller or even negative value is better for short time controls
+        // Bigger value is better for long time controls
+        if (ss->ttPv)
+            r += 1024;
+
         // Step 14. Pruning at shallow depth.
         // Depth conditions are important for mate finding.
         if (!rootNode && pos.non_pawn_material(us) && !is_loss(bestValue))
@@ -1156,7 +1162,7 @@ moves_loop:  // When in check, search starts here
 
         // Decrease reduction for PvNodes (*Scaler)
         if (ss->ttPv)
-            r -= 1037 + (ttData.value > alpha) * 965 + (ttData.depth >= depth) * 960;
+            r -= 2061 + (ttData.value > alpha) * 965 + (ttData.depth >= depth) * 960;
 
         if (PvNode)
             r -= 1018;