Simplify away depth condition for aspiration window adjust

Simplification STC:
https://tests.stockfishchess.org/tests/view/64351654596a20f264276ded
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 374664 W: 98942 L: 99089 D: 176633
Ptnml(0-2): 1049, 41767, 101878, 41558, 1080

Simplification LTC:
https://tests.stockfishchess.org/tests/view/6439499f605991a801b4f684
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 457880 W: 123021 L: 123233 D: 211626
Ptnml(0-2): 166, 44739, 139335, 44541, 159

closes https://github.com/official-stockfish/Stockfish/pull/4534

Bench: 3879281

diff --git a/src/search.cpp b/src/search.cpp
index 5205fb5729b5799e96310b70682607fdac73ce03..e322a1c99aa5ca094c05ec186ce54dcfe55f862b 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -288,9 +288,7 @@ void Thread::search() {
 
   ss->pv = pv;
 
-  bestValue = delta = alpha = -VALUE_INFINITE;
-  beta = VALUE_INFINITE;
-  optimism[WHITE] = optimism[BLACK] = VALUE_ZERO;
+  bestValue = -VALUE_INFINITE;
 
   if (mainThread)
   {
@@ -349,18 +347,15 @@ void Thread::search() {
           selDepth = 0;
 
           // Reset aspiration window starting size
-          if (rootDepth >= 4)
-          {
-              Value prev = rootMoves[pvIdx].averageScore;
-              delta = Value(10) + int(prev) * prev / 16502;
-              alpha = std::max(prev - delta,-VALUE_INFINITE);
-              beta  = std::min(prev + delta, VALUE_INFINITE);
-
-              // Adjust optimism based on root move's previousScore
-              int opt = 120 * prev / (std::abs(prev) + 161);
-              optimism[ us] = Value(opt);
-              optimism[~us] = -optimism[us];
-          }
+          Value prev = rootMoves[pvIdx].averageScore;
+          delta = Value(10) + int(prev) * prev / 16502;
+          alpha = std::max(prev - delta,-VALUE_INFINITE);
+          beta  = std::min(prev + delta, VALUE_INFINITE);
+
+          // Adjust optimism based on root move's previousScore
+          int opt = 120 * prev / (std::abs(prev) + 161);
+          optimism[ us] = Value(opt);
+          optimism[~us] = -optimism[us];
 
           // Start with a small aspiration window and, in the case of a fail
           // high/low, re-search with a bigger window until we don't fail