From af7412e58a4ce374b5035d9bb1e8c47a108ff352 Mon Sep 17 00:00:00 2001
From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Sun, 25 Dec 2016 10:34:48 +0100
Subject: [PATCH] Explicitly use alpha+1 for beta in NonPV search (#939)

Fixes the only exception, in razoring.

The code already does assert(PvNode || (alpha == beta - 1)), and it can be verified by studying the program flow that this is indeed the case, also for the modified line.

No functional change.
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index a17a7506..8089130e 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -721,7 +721,7 @@ namespace {
         &&  eval + razor_margin[depth / ONE_PLY] <= alpha)
     {
         if (depth <= ONE_PLY)
-            return qsearch<NonPV, false>(pos, ss, alpha, beta);
+            return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
 
         Value ralpha = alpha - razor_margin[depth / ONE_PLY];
         Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
-- 
2.39.2