Simplify aspiration window

Don't modify alpha window on fail-high

Bench: 5875983

Closes #1172

diff --git a/src/search.cpp b/src/search.cpp
index 4551c39d4402eaa995c9a5ebeab8ffdb47e88a06..6e5d6ab3dae5e8b04d7db201c513b6ff74aecfa3 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -437,10 +437,7 @@ void Thread::search() {
                   }
               }
               else if (bestValue >= beta)
-              {
-                  alpha = (alpha + beta) / 2;
                   beta = std::min(bestValue + delta, VALUE_INFINITE);
-              }
               else
                   break;
 
@@ -1061,8 +1058,8 @@ moves_loop: // When in check search starts from here
                   ++static_cast<MainThread*>(thisThread)->bestMoveChanges;
           }
           else
-              // All other moves but the PV are set to the lowest value: this is
-              // not a problem when sorting because the sort is stable and the
+              // All other moves but the PV are set to the lowest value: this
+              // is not a problem when sorting because the sort is stable and the
               // move position in the list is preserved - just the PV is pushed up.
               rm.score = -VALUE_INFINITE;
       }