From ca6ce6398b1bd21ff2ac29b2dc27d7c25abbb509 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Thu, 18 Apr 2019 22:10:43 +0200
Subject: [PATCH 1/1] Revert "Revert "Shuffle detection #2064""

This reverts commit 5928cb2b300baafb040495ce41f9a5f42132d141.
---
 src/search.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/search.cpp b/src/search.cpp
index 15e88ca4..95b14021 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -607,6 +607,15 @@ namespace {
             : ttHit    ? tte->move() : MOVE_NONE;
     ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY);
 
+    // if position has been searched at higher depths and we are shuffling, return value_draw
+    if (pos.rule50_count() > 36
+        && ss->ply > 36
+        && depth < 3 * ONE_PLY
+        && ttHit
+        && tte->depth() > depth
+        && pos.count<PAWN>() > 0)
+        return VALUE_DRAW;
+
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && ttHit
@@ -924,6 +933,10 @@ moves_loop: // When in check, search starts from here
                && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
           extension = ONE_PLY;
 
+      // Shuffle extension
+      else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode)
+          extension = ONE_PLY;
+
       // Castling extension
       else if (type_of(move) == CASTLING)
           extension = ONE_PLY;
-- 
2.39.2