From: Stéphane Nicolet <cassio@free.fr>
Date: Fri, 16 Sep 2016 16:18:53 +0000 (+0200)
Subject: Swap mg and eg in internal representation of Score
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=ea41f18e6e6404a6135d98eaeccfbeb177d5a49d

Swap mg and eg in internal representation of Score

Instrumentation shows that in make_score(mg, eg) calls, the mg value is
zero in 25,9% of the calls while the eg value is zero in 36,8% of the
calls.

Swapping the internal fields of mg and eg in the internal
representation of Score allows the compiler to optimize away the shift
in (eg << 16) + mg in more cases, thus resulting in a 0.3% speed-up
overall.

No functional change
---

diff --git a/src/types.h b/src/types.h
index 3aafb5c3..e5a7035c 100644
--- a/src/types.h
+++ b/src/types.h
@@ -265,22 +265,22 @@ enum Rank {
 enum Score : int { SCORE_ZERO };
 
 inline Score make_score(int mg, int eg) {
-  return Score((mg << 16) + eg);
+  return Score((eg << 16) + mg);
 }
 
 /// Extracting the signed lower and upper 16 bits is not so trivial because
 /// according to the standard a simple cast to short is implementation defined
 /// and so is a right shift of a signed integer.
-inline Value mg_value(Score s) {
+inline Value eg_value(Score s) {
 
-  union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s + 0x8000) >> 16) };
-  return Value(mg.s);
+  union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s + 0x8000) >> 16) };
+  return Value(eg.s);
 }
 
-inline Value eg_value(Score s) {
+inline Value mg_value(Score s) {
 
-  union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s)) };
-  return Value(eg.s);
+  union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s)) };
+  return Value(mg.s);
 }
 
 #define ENABLE_BASE_OPERATORS_ON(T)                             \