Simple razoring: depth 1 only, no distinction between PV / NonPV

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 8f7d263aa0367973286914920c6c231b49be1ebb..bd5eb2608cfa6714879d2cfd33b0e87ef5bc8a7c 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -66,7 +66,7 @@ namespace {
   constexpr int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
 
   // Razor and futility margins
-  constexpr int RazorMargin[] = {0, 590, 604};
+  constexpr int RazorMargin = 600;
   Value futility_margin(Depth d, bool improving) {
     return Value((175 - 50 * improving) * d / ONE_PLY);
   }
@@ -730,15 +730,9 @@ namespace {
     }
 
     // Step 7. Razoring (~2 Elo)
-    if (  !PvNode
-        && depth < 3 * ONE_PLY
-        && eval <= alpha - RazorMargin[depth / ONE_PLY])
-    {
-        Value ralpha = alpha - (depth >= 2 * ONE_PLY) * RazorMargin[depth / ONE_PLY];
-        Value v = qsearch<NonPV>(pos, ss, ralpha, ralpha+1);
-        if (depth < 2 * ONE_PLY || v <= ralpha)
-            return v;
-    }
+    if (   depth < 2 * ONE_PLY
+        && eval <= alpha - RazorMargin)
+        return qsearch<NT>(pos, ss, alpha, beta);
 
     improving =   ss->staticEval >= (ss-2)->staticEval
                || (ss-2)->staticEval == VALUE_NONE;