From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Sun, 10 Dec 2017 15:46:57 +0000 (+0100)
Subject: Make staticEval independent of the search path
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=f6981b1321357866e7aff688572e1d0e1fe57c08

Make staticEval independent of the search path

Current master can yield different staticEvals depending on the path
used to reach the position. The reason for this is that the evaluation after a
null move is always computed subtracting 2 * Eval::Tempo, while this is not
the case for lazy or specialized evals. This patch always adds tempo to evals,
which doesn't affect playing strength:

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 59911 W: 7616 L: 7545 D: 44750

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 104947 W: 18897 L: 18919 D: 67131

Fixes issue #1335

Bench: 5208264
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 47a65c59..d9c306e8 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -891,7 +891,7 @@ namespace {
         Trace::add(TOTAL, score);
     }
 
-    return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
+    return pos.side_to_move() == WHITE ? v : -v; // Side to move point of view
   }
 
 } // namespace
@@ -903,7 +903,7 @@ Score Eval::Contempt = SCORE_ZERO;
 
 Value Eval::evaluate(const Position& pos)
 {
-   return Evaluation<>(pos).value();
+   return Evaluation<>(pos).value() + Eval::Tempo;
 }
 
 /// trace() is like evaluate(), but instead of returning a value, it returns
@@ -914,7 +914,7 @@ std::string Eval::trace(const Position& pos) {
 
   std::memset(scores, 0, sizeof(scores));
 
-  Value v = Evaluation<TRACE>(pos).value();
+  Value v = Evaluation<TRACE>(pos).value() + Eval::Tempo;
   v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
 
   std::stringstream ss;