Better document razoring

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 0ee25bca1b421a159e60071e2d0d482fb3903b91..056dc250377a9ecf8ae63ab3270247f3cc331da3 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -600,11 +600,9 @@ namespace {
         &&  abs(beta) < VALUE_MATE_IN_MAX_PLY
         && !pos.pawn_on_7th(pos.side_to_move()))
     {
-        Value rbeta = beta - razor_margin(depth);
-        Value v = qsearch<NonPV, false>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
-        if (v < rbeta)
-            // Logically we should return (v + razor_margin(depth)), but
-            // surprisingly this performed slightly weaker in tests.
+        Value ralpha = alpha - razor_margin(depth);
+        Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+        if (v <= ralpha)
             return v;
     }